Note: Descriptions are shown in the official language in which they were submitted.
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Anodic oxidation of organic substrates in the presence of nucleophiles
Description
This invention refers to a process of anodic substitution comprising
electrolyzing the liquid reac-
tion medium in an electrochemical cell comprising a cathode and an anode,
whereas the liquid
reaction medium comprises an organic compound with at least one carbon bound
hydrogen
atom, a nucleophilic agent, and an ionic liquid in a proportion of at least 10
% by weight, and
whereas the said hydrogen atoms are replaced at least partially with the
nucleophilic group of
said nucleophilic agent. In a preferred embodiment of the invention, a gas
diffusion layer elec-
trode is used as anode. Preferred nucleophilic agents are aliphatic alcohols
and aliphatic car-
boxylic acids. Preferred ionic liquids are quaternary ammonium compounds
having a melting
point of less than 200 C at atmospheric pressure (1 bar).
The anodic oxidation (in the context of this invention also referred to as
electrochemical oxida-
tion) of a substrate in the presence of nucleophile is an important reaction
type in organic elec-
trochemistry which allows for an anodic substitution. Different nucleophiles
are used in this syn-
thetic valuable electrolysis (Eberson & Nyberg, Tetrahedron 1976, 32, 2185).
With alcanols like
methanol an alkoxylation of a substrate can be carried out (EP 1348043 B, EP
1111094 A).
With acids like HCOOH, CH3COOH or CF3COOH an acyloxylation of a substrate is
possible (EP
1111094 A). Also the fluorination is known as one way for a selective
introduction of fluorine.
(Fuchigami, Organic Electrochemistry, 4th edn., (Eds.: Lund & Hammerich),
Dekker, New York,
2001, p. 1035). In general this anodic substitution works nicely if the first
step the removal of an
electron from the substrate renders a stable enough cation radical so that an
attack of a nucleo-
phile can lead to the substituted product.
Anodic substitution is used at industrial scale for example in the double
methoxylation of me-
thylsubstituted aromatic compounds leading to the corresponding acetals. The
first methoxyla-
tion step renders the ether as intermediate and the following methoxylation
leads to the acetal in
one cell/process. By this elegant way aromatic aldehydes are synthesized from
toluene deriva-
tives like p-tert-butyl benzaldehyde from p-tert-butyl toluene (DE 2848397).
But there are also drawbacks to this electrosynthesis which is shown for
example in the limited
substrate range for the acetalization of methylsubstituted aromatic compounds.
The acetaliza-
tion of p-substituted toluene derivatives is only successful if the
substituent is electron pushing
like the tert-butyl group in the industrial example above. Though if the p-
substituent is non elec-
tron pushing the selectivity is very low. This problem was not solved in
decades.
Also an obvious problem for an anodic substitution is if the reaction of the
nucleophile with the
substrate follows an undesired reaction path, e.g. cyclic compounds like
ethylene carbonate
react with nucleophiles under ring opening. Therefore a substitution at the
ethylene carbonate
ring generally has not been carried out by a nucleophilic but a radical
pathway.
Unexpectedly, a method was found to improve anodic substitution in general
(conversion rate,
selectivity, current yield and accessibility of a broad range of organic
compounds for anodic
substitution) by use high ionic liquid electrolyte concentration.
This method also allows for anodic substitution of organic compounds which are
prone to nu-
cleophilic side reactions such as the ring-opening reaction of cyclic
carbonates.
The invention provides a process of anodic substitution comprising the steps
of:
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a) providing an organic compound comprising at least one hydrogen atom
bound to a car-
bon atom;
b) providing, in an electrochemical cell comprising a cathode and an anode,
a liquid reac-
tion medium comprising the organic compound and a nucleophilic agent;
c) electrolyzing the liquid reaction medium to cause replacement of at
least a part of said
hydrogen atoms with the nucleophilic group of the nucleophilic agent,
characterized in that the liquid reaction medium additionally comprises ionic
liquid in a propor-
tion of at least 10 % by weight.
The process of anodic substitution is special case of electrochemical
oxidation.
It is a critical feature of the process according to the invention to employ a
liquid reaction medi-
um that comprises ionic liquid in a proportion of at least 10 % by weight.
In the context of the present invention, the term ionic liquid refers to salts
(compounds of cations
and anions) which at atmospheric pressure (1 bar) have a melting point of less
than 200 C,
preferably less than 150 C, particularly preferably less than 100 C.
Possible ionic liquids also include mixtures of different ionic liquids.
Preferred ionic liquids comprise an organic compound as cation (organic
cation). Depending on
the valence of the anion, the ionic liquid can comprise further cations,
including metal cations, in
addition to the organic cation. The cations of particularly preferred ionic
liquids are exclusively
an organic cation or, in the case of polyvalent anions, a mixture of different
organic cations.
Suitable organic cations comprise, in particular, heteroatoms such as
nitrogen, sulfur, oxygen or
phosphorus; in particular, the organic cations comprise an ammonium group
(ammonium cati-
ons), an oxonium group (oxonium cations), a sulfonium group (sulfonium
cations) or a phos-
phonium group (phosphonium cations).
In a particular embodiment, the organic cations of the ionic liquids are
ammonium cations,
which for the present invention are
- non-aromatic compounds having a localized positive charge on the nitrogen
atom, e.g.
compounds having tetravalent nitrogen (quaternary ammonium compounds) or
- compounds having trivalent nitrogen, with one bond being a double bond,
or
- aromatic compounds having a delocalized positive charge and at least one
nitrogen at-
om, preferably from one to three nitrogen atoms, in the aromatic ring system.
Preferred organic cations are quaternary ammonium cations, preferably those
having three or
four aliphatic substituents, particularly preferably C1-C12-alkyl groups, on
the nitrogen atom; the-
se aliphatic substituents may optionally be substituted by hydroxyl groups.
In the context of the present invention, the expression C1-C12-alkyl comprises
straight-chain or
branched and saturated or unsaturated C1-C12-alkyl groups. Preferably, the C1-
C12-alkyl groups
are saturated.
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Preference is likewise given to organic cations which comprise a heterocyclic
ring system hav-
ing from one to three, in particular one or two, nitrogen atoms as
constituents of the ring system.
Monocyclic, bicyclic, aromatic or nonaromatic ring systems are all possible.
Mention may be
made by way of example of bicyclic systems as described in WO 2008/043837. The
bicyclic
systems of WO 2008/043837 are diazabicyclo derivatives, preferably formed by a
7-membered
ring and a 6-membered ring, which comprise an amidinium group; particular
mention may be
made of the 1,8-diazabicyclo(5.4.0)undec-7-enium cation.
Particularly preferred ammonium cations are quaternary ammonium cations,
imidazolium cati-
ons, pyrimidinium cations and pyrazolium cations.
The ionic liquids can comprise inorganic or organic anions. Such anions are
described, for ex-
ample, in the abovementioned WO 03/029329, WO 2007/076979, WO 2006/000197 and
WO
2007/128268.
Preference is given to anions from the group of
alkylsulfates of the formula Ra0503-,
where Ra is a C1-C12-alkyl group, a perfluorinated C1-C12-alkyl group, or a C6-
Cio-aryl
group, preferably a C1-C6-alkyl group, a perfluorinated C1-C6-alkyl group, or
a Cs-aryl
group (tosylate);
alkylsulfonates of the formula Ra503-,
where Ra is a C1-C12-alkyl group, preferably a C1-C6-alkyl group;
bisalkylsulfonylimides of the formula(Ra502)2N-,
where Ra is a C1-C12-alkyl group or a perfluorinated C1-C12-alkyl group,
preferably a
C1-C6-alkyl group or a perfluorinated C1-C6-alkyl group;
halides, in particular chloride, bromide or iodide;
pseudohalides such as thiocyanate, dicyanamide;
carboxylates of the formula Ra000-,
where Ra is a C1-C12-alkyl group, preferably a C1-C6-alkyl group, in
particular acetate;
phosphates, in particular the dialkyl phosphates of the formula RaRbPO4-,
where Ra and Rb are each, independently of one another, a C1-C6-alkyl group;
in particu-
lar, Ra and Rb are the same alkyl group (e.g. dimethyl phosphate or diethyl
phosphate);
and
phosphonates, in particular monoalkyl phosphonates of the formula RaP03-,
where Ra is a C1-C6-alkyl group.
Suitable ionic liquids in the context of the present invention are e.g.
ammoniumtetraalkyl alkyl-
sulfate (such as methyltributylammonium methylsulfate (MTBS)) or
ammoniumtetraalkyl
bis(alkylsulfonyl)imide (such as methyltributylammonium
bis(trifluoromethylsulfonyl)imide (MTB-
TFSI) or tetraoctylammonium bis(trifluoromethylsulfonyl)imide).
The proportion of the ionic liquid or the mixture thereof should be high at
least 10 % by weight,
preferably at least 25 % by weight, more preferably at least 50 % by weight,
particularly at least
65 % by weight based on the entire liquid reaction medium.
As anode and cathode any electrode suitable for electrochemical oxidation
processes can be
used. A person skilled in the art can determine which electrode is suitable.
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In a preferred embodiment of the invention, at least one gas diffusion layer
electrode is em-
ployed as anode.
Gas diffusion layer (GDL) electrodes are known from fuel cell technology and
consist of a sub-
strate and a microporous layer containing carbon particles as main component.
Suitable GDLs
are described inter alia in US 4,748,095, US 4,931,168 and US 5,618,392. The
teaching of
those documents is incorporated herein by reference. Suitable GDLs are
commercial available
e.g. from Ballard Power Systems Inc., Freudenberg FOOT KG (e.g. the g. of the
H2315 series)
or SGL Group.
A GDL generally comprises a fibre layer or substrate and a microporous layer
(MPL) consisting
of carbon particles attached to each other. The degree of hydrophobization can
vary in such a
way that wetting and gas permeability can be adjusted.
GDL electrodes for the process of the invention preferably do not contain a
catalyst supported
on the surface of the electrode.
GDL electrodes for the process of the invention contain a substrate and a
microporous layer
containing carbon particles preferable carbon black as main component.
GDL electrodes for the process of the invention can be manufactured according
to US
6,103,077, eventually using commercially available components like substrate
and carbon parti-
cles.
Preferably, the cathode is selected from Pt, Pb, Ni, graphite, felt materials
like coal or graphite
felts, stainless steel and GDL electrodes.
The organic compound provided in step a) of process according to the present
invention can
generally be any organic compound that comprises at least one hydrogen atom
directly bound
to a carbon atom that can be substituted by a nucleophilic group under the
conditions of the
anodic substitution. It is of course also possible to employ a mixture of
organic compounds.
Suitable are organic compounds that in combination with at least one
nucleophilic agent, with
ionic liquid in a proportion of at least 10 % by weight and optionally with
solvents and/or addi-
tives allow the formation of a liquid reaction medium with ionic conductivity
so that electrolysis
can be applied to cause the anodic substitution.
Preferably, the hydrogen atom is directly bound to a carbon atom is part of an
alkyl group, more
preferably. According to the invention 1, 2 or 3 hydrogen atoms are directly
bound to said car-
bon atom. Preferably, said carbon atom is a tertiary carbon atom of an alkane
or a cycloalkane,
an allylic carbon atom of an alkene or a cycloalkene or corresponding diens, a
carbon atom in
a-position to the arene moiety of an alkylarene, a carbon atom in a-position
to the nitrogen atom
of an amide, or a carbon atom in a-position to the oxygen atom of an ether.
Preferably, the organic compound according to the invention exhibits an alkyl
or alkylen group
having at least one hydrogen atom directly bound to a carbon atom.
Particularly preferred or-
ganic compounds are (i) alkanes or cycloalkanes having at least one hydrogen
atom directly
bound to a tertiary carbon atom, (ii) alkenes or cycloalkenes or corresponding
dienes having at
least one hydrogen atom directly bound to an allylic carbon atom, (iii)
alkylarenes having at
least one hydrogen atom directly bound to a carbon atom in a-position to the
arene moiety, (iv)
amides having at least one hydrogen atom directly bound to a carbon atom in a-
position to the
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nitrogen atom, or (v) ethers, esters, carbonates or acetals having at least
one hydrogen atom
directly bound to a carbon atom in a-position to the oxygen atom.
The organic compound can comprise functional groups that are essentially
stable under the
reaction conditions. Suitable functional groups comprise carbonyl,
thiocarbonyl, ester, thioester,
5 amide, oxycarbonyloxy, urethane, urea, hydroxyl, sulfonyl, sulfinate,
sulfonate, sulfate, ether,
amine, nitrile, etc. and combinations thereof.
In one embodiment of the present invention, the organic compound provided in
step a) is se-
lected from compounds of the general formula I
0
,1 ,2
I-< 1-<
X 0 (I)
wherein
X is 0, N-R3 or CR4R5,
R1 is selected from C1-C6-alkyl, C1-C6-alkoxy-C1-C6-alkyl, formyl, C1-C6-
alkylcarbonyl and Ci-
C6-alkyloxycarbonyl,
wherein R1 may also be C1-C6-alkoxy if X is a CR4R5 group,
wherein R1 may also be Ci-C6-alkylcarbonyloxy if X is a N-R3 or CR4R5 group,
R2 is selected from hydrogen, Ci-C6-alkyl, Ci-C6-alkoxy-Ci-C6-alkyl, C6-
Cio-aryl-Ci-C6-alkyl,
C3-C12-cycloalkyl and C6-Cio-aryl,
R3 is selected from hydrogen, Ci-C6-alkyl, C1-C6-alkoxy-C1-C6-alkyl,
formyl, 01-06-
alkylcarbonyl and C1-C6-alkyloxycarbonyl,
R4 and R5 are independently selected from hydrogen, C1-C6-alkyl, C1-C6-alkoxy-
C1-C6-alkyl and
C1-C6-alkoxy,
or R1 and R2 together with the X-(C=0)-0 group to which they are bound
form a 5- to 7-
membered heterocyclic ring, which may contain at least one additional
heteroatom or het-
eroatom containing group, selected from 0, S, NRc or 0=0, wherein Rc is
selected from
hydrogen, alkyl, cycloalkyl and aryl,
or X is a CR4R5 group and R1 and R4 together with the carbon atom to
which they are bound
form a 3 to 7 membered carbocyclic ring.
Preferably, X is 0, CH2 or NR3, wherein R3 is 01-04-alkyl or Ci-04-
alkylcarbonyl.
In a preferred embodiment, R1 and R2 together with the X-(C=0)-0 group to
which they are
bound form a 5 to 7 membered heterocyclic ring, which may contain at least one
additional het-
eroatom or heteroatom containing group, selected from 0, S, NRc or 0=0,
wherein Rc is select-
ed from hydrogen, alkyl, cycloalkyl or aryl. In this embodiment, X is
preferably 0, CH2 or NR3,
wherein R3 is 01-04-alkyl or Ci-04-alkylcarbonyl. Further, in this embodiment
R1 and R2 together
are selected from groups of the formulae -0H2-0H2-, -0H2-0H2-0H2- and -
CH(CxH2,0-1)-CH2-,
wherein xis 1, 2, 3 or 4.
In a further preferred embodiment, the organic compound provided in step a) is
selected from
compounds of the general formula la
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0
1
xX
0
\
A ( R6
H
(la)
wherein
X is 0, CH2 or NR3, wherein R3 is 01-C4-alkyl or 01-04-alkylcarbonyl,
A is an alkylene group selected from -CH2-, -CH2-CH2-, -CH2-CH2-CH2-, -
CHR7-, -CHR7-
CH2-,
-CH2-CHR7-, -CHR7-CH2-CH2-, -CH2-CHR7-CH2-, and -CH2-CH2-CHR7-, wherein R7is
Ci-
Cs-alkyl,
R6 is hydrogen or 01-C6-alkyl.
Preferably, X is 0 or -CH2-, A is -CH2- or -CHR7-, wherein R7 is 01-04-alkyl,
and R6 is hydrogen
or Ci-C4-alkyl.
Examples of suitable organic compounds of the general formulas I and la are
ethylene car-
bonate, propylene carbonate (4-methyl-1,3-dioxolan-2-one) and gamma
butyrolactone.
In one embodiment of the present invention, the organic compound provided in
step a) is se-
lected from compounds of the general formula II
Z-CHR8R9 (II)
wherein
Z is selected from 06-010-aryl, substituted 06-010-aryl, 01-06-allyl, -
NR10R11 group, and 01-
06-alkoxy,
R8 is selected from hydrogen, 01-06-alkyl, 01-06-alkoxy-01-06-alkyl,
wherein R8 may also be 01-06-alkoxy if Z is a 06-C10-aryl or 01-06-allyl,
R9 is selected from hydrogen, 01-06-alkyl, 01-06-alkoxy, 01-06-alkoxy-01-
06-alkyl, 06-010-
aryl, substituted 06-010-aryl, 06-Cio-aryl-C1-06-alkyl, and 03-012-cycloalkyl,
or
R8 and R9 together form a 04-07-alkylen or a 04-07-alkenylen, and
R1 and R" are independently selected from hydrogen, 01-06-alkyl, 06-010-aryl,
substituted 06-
Cio-aryl, and 01-06-alkylcarbonyl
or wherein
Z, Wand R9 are independently a 01-06-alkyl.
Preferably, Z is 06-C10-aryl or substituted 06-010-aryl, and R8 and R9
areindependently selected
from hydrogen, 01-06-alkyl and 01-06-alkoxy, particularly preferably, Z is 06-
C10-aryl or substi-
tuted 06-010-aryl, and Wand R9 areindependently selected from hydrogen, 01-04-
alkyl and 01-
04-alkoxy.
Also preferably, Z is 01-06-alkoxy, R8 is selected from hydrogen and 01-06-
alkyl, and R9 is se-
lected from hydrogen, 01-06-alkyl, 01-06-alkoxy, 06-010-aryl, and substituted
06-010-aryl, par-
ticularly preferably, Z is 01-04-alkoxy, R8 is selected from hydrogen and 01-
04-alkyl, and R9 is
selected from hydrogen, 01-04-alkyl, 01-04-alkoxy, 06-010-aryl, and
substituted 06-010-aryl.
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Examples of suitable organic compounds of the general formula II are toluene,
benzyl methyl
ether and benzaldehyde dimethylacetal.
In the context of the present invention, the expression C1-C6-alkyl comprises
straight-chain or
branched and saturated or unsaturated C1-C6-alkyl groups. Preferably, the C1-
C6-alkyl groups
are saturated. Examples of C1-C6-alkyl groups are methyl, ethyl, n-propyl,
isopropyl, n-butyl,
isobutyl, sec-butyl, tert-butyl, n-pentyl, neo-pentyl and n-hexyl.
The above remarks regarding alkyl also apply to the alkyl moiety in alkoxy.
In the context of the present invention, the term "cycloalkyl" denotes a
cycloaliphatic radical hav-
ing usually from 3 to 12 carbon atoms, preferably 5 to 8 carbon atoms, such as
cyclopropyl,
cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, norbornyl,
bicyclo[2.2.2]octyl or ad-
amantyl.
In the context of the present invention, the term C6-Cio-aryl refers to mono-
or polycyclic aro-
matic hydrocarbon radicals. C6-Cio-aryl is preferably phenyl or naphthyl.
In the context of the present invention, the term substituted C6-Cio-aryl
refers to mono- or poly-
cyclic aromatic hydrocarbon radicals having 1 to 3 aromatic hydrogen atoms,
preferably having
1 hydrogen atom substituted. Preferably, the substituents are independently
selected from Ci-
Cs-alkyl and C1-C6-alkoxy. Preferably, the substituent is in p-position.
Examples of such substit-
uents are p-methoxy, p-t-butyl or p-methyl.
In step b) of the process according to the invention, a liquid reaction medium
comprising ionic
liquid in a proportion of at least 10 % by weight, the organic compound and a
nucleophilic agent
is provided.
The nucleophilic agent employed in step b) can be any agent or mixtures of
agents which pro-
vides a nucleophile which is stabile under the electrolysis conditions and
which is capable to
substitute a hydrogen atom of the organic compound with a nucleophilic group
during the anod-
ic substitution.
A general formula for the anodic substitution according to the invention is
R-H +Nu- 4 R-Nu + H+ + 2 e-,
whereas R-H is the organic compound as specified above and Nu- is the
nucleophile. Important-
ly, the left side of this formula contains two species that would not react
with each other where it
not for the fact that two electrons are removed from the system.
The nucleophile represented by Nu- is not necessarily negatively charged. A
nucleophile in the
context of the invention may also be e.g. pyridine (C5H5N). In such a case a
positively charged
substitution product is gained.
Nucleophilic agents in the context of the present invention are compounds
which possess a
nucleophilic group. The nucleophilic group or the nucleophilic agent itself
can act as nucleophile
in a nucleophilic substitution reaction with the organic compound having at
least one hydrogen
atom bound to an electrophilic carbon atom. In the course of the nucleophilic
substitution reac-
tion said hydrogen atom is replaced with the nucleophilic group. In certain
cases the nucleo-
philic group is identical to the nucleophilic agent (e.g. pyridine (C5H5N)).
In the context of the
present invention, the term nucleophile refers to the attacking agent (e.g.
C5H5N, RO- and
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R000-, but also ROH, RCOOH), whereas the term nucleophilic group refers to the
replacement
group (e.g. RO- or Rcoa but not ROH or RCOOH).
Preferred nucleophiles of the present invention are selected from the group
consisting of HO-,
RO-, ROH, R000-, RCOOH, NO2-, NO3-, N3-, OCN-, SCN-,RS03-, SeCN-, ON-, CI-,
Br, and I-,
whereas R represents an alkyl or arly group, preferably an alkyl group.
Particularly preferred
nucleophiles of the present invention are RO- , ROH, R000-, or RCOOH.
Anodic substitutions employing the nucleophiles Ha, Ra, R000-, or NO3- result
in the for-
mation of 0-0 bonds:
R-H + R'COO-, R-000R' + H+ + 2 e- (anodic acyloxylation)
R-H + R'0-, R-OR' + H+ + 2 e- (anodic alkoxylation)
R-H + HO-, R-OH + H+ + 2 e- (anodic hydroxylation)
R-H + NO3-, R-0NO2+ H+ + 2 e- (anodic nitratation)
R-H + R'S03-, R-OSO2R' + H+ + 2 e-
Anodic substitutions employing the nucleophiles N3-, OCN-, or NO2- result in
the formation of 0-
N bonds:
R-H + N3- -> R-N3 + H+ + 2 e- (anodic azidation)
R-H + OCN-, R-NCO + H+ + 2 e-
R-H + NO2-, R-NO2+ H+ + 2 e- (anodic nitration)
Anodic substitution employing the nucleophile ON- results in the formation of
a C-C bond:
R-H + ON-, R-ON + H+ + 2 e- (anodic cyanation)
Nucleophilic agents in the context of the present invention are compounds
which possess a
nucleophilic group, e.g. water (with the nucleophilic group HO-), alcohols
(e.g. of the formula
ROH with the nucleophilic group RO-), carboxylic acids (e.g. of the formula
RCOOH with the
nucleophilic group R000-), nitrous acid or salts thereof (with the
nucleophilic group NO2-), nitric
acid or salts thereof (with the nucleophilic group NO3-), hydrazoic acid or
salts thereof (with the
nucleophilic group N3-), isocyanic acid or salts thereof (with the
nucleophilic group OCN-),
isothiocyanic acid or salts thereof (with the nucleophilic group SON),
sulfonic acid (e.g. of the
formula RSO3H with the nucleophilic group R503-), isoselenocyanic acid or
salts thereof (with
the nucleophilic group SeCN-), hydrogen cyanide or salts thereof (with the
nucleophilic group
ON-), hydrogen chloride or salts thereof (with the nucleophilic group 01-),
hydrogen bromide or
salts thereof (with the nucleophilic group Br), or hydrogen iodide or salts
thereof (with the nu-
cleophilic group I-), whereas R represents an alkyl or arly group, preferably
an alkyl group.
Preferred nucleophilic agents of the present invention are alcohols of the
formula III
R120H (III)
or carboxylic acids of the formula IV
R13000H (IV),
where R12 and R13 are 01-012-alkyl or 01-012-perfluorinated alkyl, preferably
01-06-alkyl or Ci-
06-perfluorinated alkyl, particular preferably 01-06-alkyl.
In a particular embodiment of the invention, F- is excluded from the
nucleophiles. Accordingly, in
this particular embodiment, F- providing compounds (fluorinating agents) are
excluded from the
nucleophilic agents. Also in this particular embodiment, such fluorinating
agents are excluded
from the ionic liquids.
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The molar ratio of nucleophilic agent (with regard nucleophilic group) to
organic compound is
preferably in the range from 1:1 to 99:1 (nucleophilic agent: organic
compound), more prefera-
bly from 2:1 to 99:1.
In a particular embodiment of the invention, the organic compound provided in
step a) is select-
ed from compounds of the general formula V
Y-CH2R14 (V)
wherein
Y is selected from C6-Cio-aryl, substituted C6-C10-aryl, C1-C6-allyl,
and ¨NR10R11 group,
R14 is selected from hydrogen, C1-C6-alkyl, Ci-C6-alkoxy-Ci-C6-alkyl, C6-
Cio-aryl-C1-C6-alkyl,
C6-C10-aryl, substituted C6-Cio-aryl and C3-C12-cycloalkyl,
R10 and R11 arespecified as above,
and the nucleophilic agent is an alcohol of the formula III as specified
above,
whereas in the course of the anodic substitution process two hydrogen atoms
are subsequently
replaced by ¨0R12 groups resulting in an acetal of the formula VI
Y-C(0R12)2R14 No.
In one embodiment, the invention provides a process of manufacturing an acetal
of the general
formula VI as specified above by anodic substitution comprising the steps of:
a) providing an organic compound of the general formula V as specified
above;
b) providing, in an electrochemical cell comprising a cathode and an anode,
a liquid reac-
tion medium comprising the organic compound and an alcohol of the general
formula III
as specified above;
c) electrolyzing the liquid reaction medium to cause the formation of the
acetal of the gen-
eral formula VI,
characterized in that the liquid reaction medium additionally comprises ionic
liquid in a propor-
tion of at least 10 % by weight.
Preferably, at least one gas diffusion layer electrode is employed as anode.
An example for such an acetalization process is the conversion of toluene with
methanol to
benzaldehyde dimethylacetal.
In a particular embodiment of the invention, the organic compound provided in
step a) is select-
ed from compounds of the general formula V
Y-CH2R14 (V)
wherein
Y is selected from C6-Cio-aryl, substituted C6-C10-aryl, C1-C6-allyl,
and ¨NR1 R11 group,
R14 is selected from hydrogen, C1-C6-alkyl, Ci-C6-alkoxy-Ci-C6-alkyl, C6-
Cio-aryl-C1-C6-alkyl,
C6-Cio-aryl, substituted C6-Cio-aryl and C3-C12-cycloalkyl,
R10 and R11 arespecified as above,
and the nucleophilic agent is an alcohol of the formula III as specified
above,
whereas in the course of the anodic substitution process two hydrogen atoms
are subsequently
replaced by ¨0R12 groups resulting in an acetal of the formula VI
Y-C(0R12)2R14 (VI), and
whereas the acetal of formula VI is subsequently hydrolysed resulting in an
aldehyde or ketone
of formula Via
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Y-00R14 (Via).
In one embodiment, the invention provides a process of manufacturing an
aldehyde or ketone of
the general formula Via as specified above by anodic substitution comprising
the steps of:
a) providing an organic compound of the general formula V as specified
above;
5 b) providing, in an electrochemical cell comprising a cathode and an
anode, a liquid reac-
tion medium comprising the organic compound and an alcohol of the general
formula III
as specified above;
c) electrolyzing the liquid reaction medium to cause the formation of
the acetal of the gen-
eral formula VI;
10 d) hydrolyzing the acetal of the general formula Vito cause the
formation of the aldehyde
or ketone of the general formula Via,
characterized in that the liquid reaction medium additionally comprises ionic
liquid in a propor-
tion of at least 10 % by weight.
Preferably, at least one gas diffusion layer electrode is employed as anode.
An example for such a manufacturing process is the conversion of toluene with
methanol to
benzaldehyde dimethylacetal and the subsequent hydrolysis of the benzaldehyde
dimethyla-
cetal to benzaldehyde. Hydrolysis step can be performed according to protocols
known by the
skilled person.
In the context of the present invention, the expression "liquid reaction
medium" denotes a reac-
tion medium that comprises a liquid phase under the reaction conditions of the
anodic substitu-
tion. This liquid phase contains a sufficient amount of the organic compound
to allow anodic
substitution. It is not necessary that the liquid phase contains the organic
compound in form of a
homogeneous solution, as long as a sufficient amount of the organic compound
is brought in
contact with the electrodes of the electrochemical cell, in particular the
anode. Thus, the liquid
reaction medium may contain the organic compound in form of a homogeneous
solution, colloi-
dal solution, molecularly disperse solution, emulsified phase or disperse
phase. Finally, it is also
possible to introduce a gaseous stream containing the organic compound into
the liquid reaction
medium.
The liquid reaction medium within the electrochemical oxidation cell comprises
ionic liquid in a
proportion of at least 10 % by weight based on the total liquid reaction
medium, an amount of
organic compound solubilized therein, and an amount of nucleophilic agent
solubilized therein.
The process according to the invention does not require any additional
solvents or additives to
establish a anodic substitution reaction with high conversion rates and good
selectivity. In par-
ticular, the ionic liquid employed also function as conducting salt
(electrolyte).
In one embodiment of the present invention, the liquid reaction medium
comprises in essence
no additional solvents or other additives, i.e. the proportion of solvents and
other additives is
below 1% by weight, based on the total weight of the liquid reaction medium.
If the liquid reaction medium contains an organic solvent, it is preferably
selected from acetoni-
trile, ethers, halogenated alkanes, sulfolane and mixtures thereof.
In a specific embodiment of the present invention the liquid reaction medium
comprises at least
one further additive as redox mediator and/or supportive electrolyte.
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Redox mediators are used in indirect electrolyses. Typical examples of redox
mediators are
2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), triarylamines such as tris(2,4-
dibromophenyl)amine or halogenides such as bromide or iodide (Steckhan,
Angewandte
Chemie 1986, 98,681-699).
In the present invention preferred redox mediators are bromide or iodide
salts, particular bro-
mide salts such as alkaline bromide salts or tetraalkylammonium bromide salts.
In a specific embodiment of the present invention the liquid reaction medium
comprises a bro-
mide or iodide salt as further additive. Preferably, in this specific
embodiment a GDL electrode
is employed as anode and the ionic liquid is employed in a proportion of from
30 to 70 % by
weight, preferably from 40 to 50 % by weigh based on the entire liquid
reaction medium.
Preferably, in this specific embodiment the organic compound provided in step
a) is selected
from compounds of the general formula VII
Y-CR152H (VII)
wherein
Y is specified as above,
R15 is a C1-C12-alkoxy, preferably a C1-C6-alkoxy,
and the nucleophilic agent is an alcohol of the formula III as specified
above, whereas in the
course of the anodic substitution process the hydrogen atom is replaced by the
¨0R1 group
resulting in an ortho-ester of the formula VIII
Y-CR152(0R12) (VIII).
In one embodiment, the invention provides a process of manufacturing an ortho-
ester of the
general formula VIII as specified above by anodic substitution comprising the
steps of:
a) providing an organic compound of the general formula VII as
specified above;
b) providing, in an electrochemical cell comprising a cathode and an anode,
a liquid reac-
tion medium comprising the organic compound, a bromide or iodide salt, and an
alcohol
of the general formula III as specified above;
c) electrolyzing the liquid reaction medium to cause the formation of
the acetal of the gen-
eral formula VII,
characterized in that the liquid reaction medium additionally comprises ionic
liquid in a propor-
tion of at least 10 % by weight.
Preferably, at least one gas diffusion layer electrode is employed as anode.
Such a process of mediated alkoxylation of an acetal to the ortho-ester is
improved compared to
the mediated alkoxylation processes concerning the current yield reported
within the prior art
(Grosse Brinkhaus et al., Tetrahedron, 1986, 42, 553-560).
In one embodiment of the invention, the organic compound provided in step a)
is a compound of
the general formula la as specified above and the nucleophilic agent is a
carboxylic acids of the
formula (IV) as specified above. Preferably, the nucleophilic acid within this
embodiment is a
carboxylic acid of the formula IV, wherein R13 is C4-C12-alkyl, preferably Ca-
Cs-alkyl having a
tertiary carbon atom in alpha position. This process of the invention allows
for the anodic substi-
tution of an organic compound of formula la such as e.g. ethylene carbonate or
propylene car-
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bonate with a carboxylic acid (acyloxylation) which is very surprisingly
related to the easy ring-
opening of ethylene carbonate with nucleophiles even if acids are mediocre
nucleophiles.
Accordingly, in one embodiment, the invention provides a process of
manufacturing an acylox-
ylated organic compound of the general formula lb
0
XZo
\A4--- IR6
0
0
R13
(lb)
wherein X, A, and R6 arespecified as above in the context of the general
formula la and
wherein R13 is C1-C12-alkyl or C1-C12-perfluorinated alkyl, preferably C1-C6-
alkyl or 01-06-
perfluorinated alkyl, particular preferably Ca-Cs-alkyl having a tertiary
carbon atom in a-position
by anodic substitution comprising the steps of:
a) providing an organic compound of the general formula la as specified
above;
b) providing, in an electrochemical cell comprising a cathode and an anode,
a liquid reac-
tion medium comprising the organic compound and an carboxylic acid of the
general
formula IV as specified above;
c) electrolyzing the liquid reaction medium to cause the formation of the
acyloxylated or-
ganic compound of the general formula lb,
characterized in that the liquid reaction medium additionally comprises ionic
liquid in a propor-
tion of at least 10 % by weight.
An overview on the construction possibilities of electrolysis cells that are
suitable as electro-
chemical oxidation cells for the process of the invention can be found, for
example, in Pletcher
& Walsh, Industrial Electrochemistry, 2nd Edition, 1990, London, pp. 60ff.
Suitable electrochemical cells for the electrochemical oxidation are undivided
cells and divided
cells. An undivided cell usually comprises only one electrolyte portion; a
divided cell has two or
more such portion. The individual electrodes can be connected in parallel
(monopolar) or serial-
ly (bipolar). In a suitable embodiment, the electrochemical cell employed for
the electrochemical
oxidation is a monopolar cell comprising a GDL anode and a cathode. In a
further suitable em-
bodiment, the electrochemical cell employed for the electrochemical oxidation
is a cell having
bipolar connection of the stacked electrodes.
In a preferred embodiment, the electrochemical oxidation cell is a plate-and-
frame cell. Plate-
and-frame cells employed in the process of the invention preferably comprise
at least one GDL
electrode. This type of cell is composed essentially of usually rectangular
electrode plates and
frames which surround them. They can be made of polymer material, for example
polyethylene,
polypropylene, polyvinyl chloride, polyvinylidene fluoride, PTFE, etc. The
electrode plate and
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the associated frame are frequently joined to each other to form an assembly
unit. By pressing
a plurality of such plate-and-frame units together, a stack which is assembled
according to the
constructional fashion of filter presses is obtained. Yet further frame units,
for example for re-
ceiving spacing gauzes, etc. can be inserted in the stack.
The process according to the invention can be performed according to known
methods for the
anodic substitution by electrolyzing the liquid reaction medium in order to
cause replacement of
at least a part of the carbon bound hydrogen atoms with nucleophilic groups,
with the proviso
that the employed liquid reaction medium comprises ionic liquid in a
proportion of at least 10 %
by weight.
One or more anodes and one or more cathodes are placed in the liquid reaction
medium. Ac-
cording to the invention, preferably at least the anode is a GDL electrode. An
electric potential
(voltage) is established between the anode(s) and cathode(s), resulting in an
oxidation reaction
(anodic substitution, i.e., replacement of one or more carbon bound hydrogen
atoms with car-
bon bound nucleophilic groups) at the anode, and a reduction reaction
(primarily hydrogen evo-
lution) at the cathode.
Preferably, the anodic substitution reaction is performed with a constant
current applied; i.e. at a
constant voltage and a constant current flow. It is of course also possible,
to interrupt the elec-
tric current through a current cycle, as described in US 6,267,865.
The current density applied in step c) is in ranges known to the expert.
Preferably, the current
density employed in step c) is in a range of from 10 to 250 mA/cm2, more
preferably, in the
range of from 10 to 100 mA/cm2.
The anodic substitution products can be separated from the reaction medium by
customary
methods, preferably by distillation. The distillation of the reaction
discharge can be carried out
by customary methods known to those skilled in the art. Suitable apparatuses
for the fractiona-
tion by distillation comprise distillation columns such as tray columns, which
can be provided
with bubble caps, sieve plates, sieve trays, packings, internals, valves, side
offtakes, etc. Divid-
ing wall columns, which may be provided with side offtakes, recirculations,
etc., are especially
suitable. A combination of two or more than two distillation columns can be
used for the distilla-
tion. Further suitable apparatuses are evaporators such as thin film
evaporators, falling film
evaporators, Sambay evaporators, etc, and combinations thereof.
The use of a liquid reaction medium which comprises ionic liquid in a
proportion of at least 10 %
by weight in the process of the invention has a positive effect on at least
one of the following
parameters: selectivity of the nucleophilic substitution, conversion rate of
the nucleophilic substi-
tution reaction, current yield, space-time yield, service life of the cell,
and accessibility of a
broad range of organic compounds for anodic substitution. This positive effect
is even more
pronounced if additionally a GDL electrode is used as anode. While not being
bound to any the-
ory it is assumed, that intermediates of the nucleophilic substitution
reaction of the organic
compound, e.g. cation-radicals generated during the anodic oxidation step, are
stabilized by the
ionic liquid and that this stabilization is even better if the ionic liquid is
used in combination with
a GDL anode.
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Examples
The following examples are intended for further illustration of the present
invention.
Example 1 for comparison
In a 100 ml undivided electrolysis cell 6.5 g toluene, 34.1 g methanol and 2.6
g methyltribu-
tylammonium methylsulfate (MTBS, 6 % by weight) as supporting electrolyte were
electrolyzed
for 7 F using a graphite anode (10 cm2) and a stainless steel cathode (10
cm2). The applied
current density was 34 mA/cm2. The GC analysis showed 65 % conversion of
toluene, a selec-
tivity to benzaldehyde dimethylacetal of 7 % and a current yield of 2 %. The
results of this ex-
periment are summarized in table 1.
Example 2
In a 100 ml undivided electrolysis cell 7.5 g toluene, 17.0 g methanol and
25.5 g methyltribu-
tylammonium methylsulfate (MTBS, 51 % by weight) as supporting electrolyte
were electrolyzed
for 7 F using a graphite anode (10 cm2) and a stainless steel cathode (10
cm2). The applied
current density was 34 mA/cm2. The GC analysis showed 88 % conversion of
toluene, a selec-
tivity to benzaldehyde dimethylacetal of 32 % and a current yield of 15 %. The
results of this
experiment are summarized in table 1.
Example 3
In a 100 ml undivided electrolysis cell 13.1 g toluene, 29.5 g methanol and
9.8 g methyltribu-
tylammonium methylsulfate (MTBS, 12% by weight) as supporting electrolyte were
electrolyzed
for 7 F using a GDL (10 cm2) as anode and a stainless steel cathode (10 cm2).
The current den-
sity was 34 mA/cm2. The GC analysis showed 87 % conversion of toluene, a
selectivity to ben-
zaldehyde dimethylacetal of 22 % and a current yield of 9 %. The GDL electrode
has been be
manufactured according to US 6,103,077 using carbon black. The results of this
experiment are
summarized in table 1.
Example 4
In a 100 ml undivided electrolysis cell 13.1 g toluene, 29.5 g methanol and
9.8 g methyltribu-
tylammonium methylsulfate (MTBS, 25 % by weight) as supporting electrolyte
were electrolyzed
for 7 F using a GDL (10 cm2) as anode and a stainless steel cathode (10 cm2).
The current den-
sity was 34 mA/cm2. The GC analysis showed 89 % conversion of toluene, a
selectivity to ben-
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zaldehyde dimethylacetal of 29 % and a current yield of 13 %. The GDL
electrode has been be
manufactured according to US 6,103,077 using carbon black. The results of this
experiment are
summarized in table 1.
5
Example 5
In a 100 ml undivided electrolysis cell 13.1 g toluene, 29.5 g methanol and
9.8 g methyltribu-
tylammonium methylsulfate (MTBS, 51 % by weight) as supporting electrolyte
were electrolyzed
10 for 8 F using a commercial GDL (H2315 IX11CX45 from Freudenberg, 10 cm2)
as anode and a
stainless steel cathode (10 cm2). The current density was 34 mA/cm2. The GC
analysis showed
98 % conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 45
% and a current
yield of 21 %. The results of this experiment are summarized in table 1.
Example 6
In a 100 ml undivided electrolysis cell 7.9 g toluene, 17.9 g methanol and
26.9 g methyltribu-
tylammonium methylsulfate (MTBS, 51 % by weight) as supporting electrolyte
were electrolyzed
for 7 F using a commercial GDL (Sigracet GDL 25 BC from SGL Group, 10 cm2) as
anode and
a stainless steel cathode (10 cm2). The current density was 34 mA/cm2. The GC
analysis
showed 96 % conversion of toluene, a selectivity to benzaldehyde
dimethylacetal of 45 % and a
current yield of 23 %. The results of this experiment are summarized in table
1.
Example 7
In a 100 ml undivided electrolysis cell 7.6 g toluene, 17.2 g methanol and
25.8 g methyltribu-
tylammonium methylsulfate (MTBS, 51 % by weight) as supporting electrolyte
were electrolyzed
for 6 F using a GDL (10 cm2) as anode and a stainless steel cathode (10 cm2).
The current den-
sity was 34 mA/cm2. The GC analysis showed 97 % conversion of toluene, a
selectivity to ben-
zaldehyde dimethylacetal of 48 % and a current yield of 25 %. The GDL
electrode has been be
manufactured according to US 6,103,077 using carbon black. The results of this
experiment are
summarized in table 1.
Example 8
In a 100 ml undivided electrolysis cell 8.1 g toluene, 18.3 g methanol and
27.4 g methyltribu-
tylammonium methylsulfate (MTBS, 51 % by weight) as supporting electrolyte
were electrolyzed
for 6 F using a GDL (10 cm2) as anode and a stainless steel cathode (10 cm2).
The current den-
sity was 65 mA/cm2. The GC analysis showed 94 % conversion of toluene, a
selectivity to ben-
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zaldehyde dimethylacetal of 49 % and a current yield of 27 %. The GDL
electrode has been be
manufactured according to US 6,103,077 using carbon black. The results of this
experiment are
summarized in table 1.
Example 9
In a 100 ml undivided electrolysis cell 4.9 g toluene, 10.9 g methanol and
36.8 g methyltribu-
tylammonium methylsulfate (MTBS, 70 % by weight) as supporting electrolyte
were electrolyzed
for 6 F using a graphite anode (10 cm2) and a stainless steel cathode (10
cm2). The applied
current density was 34 mA/cm2. The GC analysis showed 81 % conversion of
toluene, a selec-
tivity to benzaldehyde dimethylacetal of 30 % and a current yield of 15 %. The
results of this
experiment are summarized in table 1.
Example 10
In a 100 ml undivided electrolysis cell 5.2 g toluene, 11.7 g methanol and
39.4 g methyltribu-
tylammonium methylsulfate (MTBS, 70 % by weight) as supporting electrolyte
were electrolyzed
for 6 F using a GDL (10 cm2) as anode and a stainless steel cathode (10 cm2).
The current den-
sity was 34 mA/cm2. The GC analysis showed 93 % conversion of toluene, a
selectivity to ben-
zaldehyde dimethylacetal of 50 % and a current yield of 28 %. The GDL
electrode has been be
manufactured according to US 6,103,077 using carbon black. The results of this
experiment are
summarized in table 1.
Example 11
In a 100 ml undivided electrolysis cell 5.9 g toluene, 13.2 g methanol and
44,4 g 1-Ethyl-3-
methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMimid-TFSI, 70 % by
weight) as support-
ing electrolyte were electrolyzed for 6 F using a GDL (10 cm2) as anode and a
stainless steel
cathode (10 cm2). The applied current density was 34 mA/cm2. The GC analysis
showed 98%
conversion of toluene, a selectivity to benzaldehyde dimethylacetal of 50 %
and a current yield
of 30 %. The GDL electrode has been be manufactured according to US 6,103,077
using car-
bon black. The results of this experiment are summarized in table 1.
Example 12
In a 100 ml undivided electrolysis cell 5.6 g toluene, 12.7 g methanol and
42.8 g methyltribu-
tylammonium bis(trifluoromethylsulfonyl)imide (MTB-TFSI, 70 % by weight) as
supporting elec-
trolyte were electrolyzed for 6 F using a GDL (10 cm2) as anode and a
stainless steel cathode
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(10 cm2). The applied current density was 34 mA/cm2. The GC analysis showed 98
% conver-
sion of toluene, a selectivity to benzaldehyde dimethylacetal of 50 % and a
current yield of 32
%. The GDL electrode has been be manufactured according to US 6,103,077 using
carbon
black. The results of this experiment are summarized in table 1.
Example 13
In a 100 ml undivided electrolysis cell 6.0 g toluene, 13.5 g methanol and
45.4 g methyltribu-
tylammonium bis(trifluoromethylsulfonyl)imide (MTB-TFSI, 70 % by weight) as
supporting elec-
trolyte were electrolyzed for 5.5 F using a GDL (10 cm2) as anode and a
stainless steel cathode
(10 cm2). The applied current density was 60 mA/cm2. The GC analysis showed 95
% conver-
sion of toluene, a selectivity to benzaldehyde dimethylacetal of 54 % and a
current yield of 35
%. The GDL electrode has been be manufactured according to US 6,103,077 using
carbon
black. The results of this experiment are summarized in table 1.
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Table 1: Acetalization of toluene
Exam- Anode % IL electro- F c. d. cony. Select. c.
y.
pie lyte
[mA/cm2] [%] IN IN
1 Graphite 6 MTBS 7 34 65 7 2
2 Graphite 51 MTBS 7 34 88 32 15
3 GDL 12 MTBS 7 34 87 22 9
4 GDL 25 MTBS 7 34 89 29 13
Commercial
51 MTBS 8 34 98 45 21
GDL
Commercial
6 GDL 51 MTBS 7 34 96 45 23
7 GDL 51 MTBS 7 34 97 48 25
8 GDL 51 MTBS 6 65 94 49 27
9 Graphite 70 MTBS 6 34 81 30 15
GDL 70 MTBS 6 34 93 50 28
EMimid-
11 GDL 70 TFSI 6 34 98 50 30
12 GDL 70 MTB-TFSI 6 34 98 50 32
5.
13 GDL 70 MTB-TFSI 60 95 54 35
5
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Example 14 for comparison
In a 100 ml undivided electrolysis cell 6.7 g benzaldehyde dimethylacetal and
37.6 g methanol
and 0.45 g sodium bromide (1 % by weight) as mediator /supporting electrolyte
were electro-
lyzed for 2.5 F using graphite(10 cm2) as anode and a stainless steel cathode
(10 cm2). The
applied current density was 34 mA/cm2. The GC analysis showed 18 % conversion
of benzal-
dehyde dimethylacetal, a selectivity to benzoic acid ortho-ester of 49 % and a
current yield of 7
%.
Example 15 for comparison
In a 100 ml undivided electrolysis cell 6.1 g benzaldehyde dimethylacetal and
33.9 g methanol
and 0.82 g tetrabutyl ammonium bromide (2 % by weight) as mediator /supporting
electrolyte
were electrolyzed for 2.5 F using graphite(10 cm2) as anode and a stainless
steel cathode (10
cm2). The applied current density was 34 mA/cm2. The GC analysis showed 24 %
conversion of
benzaldehyde dimethylacetal, a selectivity to benzoic acid ortho-ester of 59 %
and a current
yield of 11 %.
Example 16
In a 100 ml undivided electrolysis cell 5.2 g benzaldehyde dimethylacetal,
21.2 g methanol, and
23.1 g methyltributylammonium methylsulfate (MTBS, 45 % by weight) and 2.2 g
tetrabutyl
ammonium bromide (4 % by weight) as mediator were electrolyzed for 5 F using a
GDL (10
cm2) as anode and a stainless steel cathode (10 cm2). The applied current
density was 34
mA/cm2. The GC analysis showed 72 % conversion of benzaldehyde dimethylacetal,
a selectivi-
ty to benzoic acid ortho-ester of 68 % and a current yield of 20 %. The GDL
electrode has been
be manufactured according to US 6,103,077 using carbon black.
Example 17
In a 100 ml undivided electrolysis cell 4.9 g benzaldehyde dimethylacetal,
20.2 g methanol, and
21.8 g methyltributylammonium methylsulfate (MTBS, 42 % by weight) and 5.1 g
tetrabutyl
ammonium bromide (10 % by weight) as mediator were electrolyzed for 5 F using
a GDL
(10 cm2) as anode and a stainless steel cathode (10 cm2). The applied current
density was 34
mA/cm2. The GC analysis showed 31 % conversion of benzaldehyde dimethylacetal,
a selectivi-
ty to benzoic acid ortho-ester of 83 % and a current yield of 10 %. The GDL
electrode has been
be manufactured according to US 6,103,077 using carbon black.
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Example 18
In a 100 ml undivided electrolysis cell 5.6 g ethylene carbonate, 27 g pivalic
acid and 22.3 g
5 tetraoctylammonium bis(trifluoromethylsulfonyl)imide (41 % by weight) as
supporting electrolyte
were electrolyzed for 4.7 F using a GDL (10 cm2) as anode and a stainless
steel cathode (10
cm2). The applied current density was 10 mA/cm2. The NMR and GC analysis
showed 67%
conversion of ethylene carbonate, the yield is 18 % of 4-(tert-butyl)
carbonyloxy-1,3-dioxolan-2-
one. The GDL electrode has been be manufactured according to US 6,103,077
using carbon
10 black.
