Note: Descriptions are shown in the official language in which they were submitted.
HO~ 75/F _06
lO~/93~
The present invention provides a novel process for the
preparation of 2-hydroxynaphthalencs by dehydrogenation of
the reaction products obtained from cyclohexanones and ~ un-
saturated ketones in the Robinson anellation.
Hitherto, the industrial-scale manufacture of 2-hydroxy-
naphthalenes consists in reacti.ng naphthalenes with sulfuric
acid, neutralizing the naphthalenesulfonic acid, fusiny the
naphthalene sulfonate with caustic soda, and liberating the
hydroxynaphthalene by means of sulfu.ric acid. The disadvan-tage
of this process resides .in the fact that large amounts of
salts (Na2SO3, Na2SO~) are inevitably formed which have to be
removed from the sewage water with great expenditure.
; Furthermore, it is known to obtain 2-hydroxynaph-thalene
by catalytic dehydroyenation of ~-tetralone. However, this
lS process yields only 26% of ~-naphthol, apart from 54% of
naphthalene.
2-hydroxynaphthalenes are important intermediate products
: for organic dyestuffs.
There has now been found a process for the preparatio.n
of 2-hydroxy-naphthalenes of the formula
R R
R ~ OH
R R
wherein the radicals R, being identical or different, are
hydrogen, aliphatic or aromatic radicals; adjacent aliphatic
radicals R optionally forming together an alicyclic 5- or
6-membered ring, which comprises heatiny cycloalkenones or
hydroxycycloalkanones of the formulae II to IV
~ 93~
R ~ ~ ~ 0 R ~ 0 R ~ ~ 0
R R R ~ R
Il III . IV
.. . . .
wherein the radicals R ar6! as defined above, in the
presence o~ a dehydrogenating agent.
The compounds o~ formulae II~ III and IV may be obtained
in known manner, ~or example ~rom ~t n-unsaturat~d ketones and
cyclic ketones such as cyclohexanones, or ~- and B-decalones
or thelr enamines or ketimi.ne~.
~ Suitable aliphatio radical~ are straight~chain, branched
or cyclic alkyl radicals, pre~erably those having up to 12
carbon atoms. Especially mcthyl, ethyl, propyl, butyl, pentyl,
hexyl, octyl, decyl, dodecyl, cyclopentyl, cyclohexyl and cy~lo-
dodecyl are pre~erred.
Generally, the radicals R together do not contain more
than 24 carbon atoms. The alkyl radioals may be subst.ituted~
for example by halogen, espec~ally fluorine or chlorine, or by
~ .
pheny}, naph~hyl,:hydroxy, methoxy5 acetoxy9 carbamide or carbo--
nitrile, but also by carbalkoxy ha~ing up to 6 carbon atoms,
for example carboxymethyl ( -coocH3 3 or carbo~yethyl (_COOC2H5).
~25~ :~ Suitable aromatic radioals are ~or example aryl groups
having~from 6~to:1~ carbon a~oms; phen~l or naphthyl being
pr~er~ed. :Th.e aryl groups may be ~ubstituted, ~or example by
ha~ogen, especially fluorine:or~chlorine, alkyl having up to
29~ 6 carbcn~atom~,~cr~by tri~luoro~ethyl or nitro, but also by
',~5~ 3 -
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~IOE 751F 006
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alkoxy having up to 6 carbon atoms such as methoxy or ethoxy.
Dehydrogenation o~ the cycloalkenones or hydroxyalka~ones
is carried out by hea-ting them in the presence of a dehydrogen-
ating agent, for example by reaction with sulfur9 selenium,
chloranil~ Pd(II) salt~ or by heating them in the presence of
a dehydrogenation catalyst/
Suitable dehydrogenation cRtalysts are for example
ruthenium~ rhodium, palladium, osmium9 iridium and platinum,
but also metals such as copper, silver, gold, iron, cobalt,
nickel and chromium~ or mixtures of these elements, as well as
also the salts thereo~. Suitable salts are ~or example
chlorides, oxides, acetates or carbonates. Preferred elements
are palladi~, platinum, ruthenium and copper, or the salts
; thereof.
The catalysts are preferably used on carriers, ~or example
on carbon9 aluminum oxide, silicic acid, magnesium oxide,
calcium oxide, titanium oxide and asbestos, or a mixture o~
two or more of the cited carriers ~ Palladium o~ carhon is
especially recommended. The concentration o~ the catalyst is
~20 advantageously from 0.02 to 20 weight %, relative to the
carrier, preferably from 0.1 to 10 weight %.
The process may be carried out in the liquid or gaseous
phase, batchwise or continuously~
Operations in the liquid phase are generally carried out
at temperatures of from 140 to 350C and under a pressure
. su~icient ~or maintaining the liquid phase. Temperatures
of ~rom 180 to 250C are preferred/ since these temperatures
ensure an e~pecially high selectivity and simultaneously a
29 ~ very rapid course of the dehydrogenation reaction.
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The reaction pressure in the case of liquid phase operation
is generally from 0.5 to 20 atmospheres, but it must be at
leas-t su~ficient for maintaining a liquid phase.
It is important to keep low the partial pressure of the
nydrogen Iormed during ihe dehydrogenaiion3 so thai ihe equi-
librium is shifted in ~avor of the dehydrogerlation and hydro-
genation or hydrogenolysis o~ I;he starting compounds and ~inal
product~ is prevented. Such a low hydrogen partial pressure
may be obtained by flushing the reaction system with an inert
gas, ~or example nitrogen or carbon dioxide.
Liquid phase operation may be carried out in the pre~ence
o~ a suitable solvent, for example aliphatic ethers, aromatic
ethers 9 such as diphenyl ether; hydrocarbons, such as benzene,
toluene, ~ylene, pseudo-cumene, naphthalene, biphenyl, tetra-
line, decaline; ketones/ such as acetone, diethylketone~ methyl-
ethylketone or methylisobu-tylketone; esters, such as cyclo-
hexyl propionate or trimethyleneglycol diacetate; but also
acid amides, for example dimethyl formamide or N-methyl-pyrro
lidone, alcohols, phenols, water or the reaction product it~
self are suitable.
P~e~erred solvents are aliphatic ethers, for example poly-
glycol dialkyl ethers, such as di.~ tri- or tetraethyleneglycol
dialkyl ethers having generally alkyl groups o~ up to 6 carbon
a*oms.
Especially advantageous are polyglycol dimethyl and di-
ethyl ethers. The polyglycol dialkyl ethers have the advantage
o~ boiling under atmospheric pressure in the pre~erred temper-
ature range of from 180 to 260C, which is extremely fa~orable
29 ~or the process of the in~ention, since it allows operating
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ilOE 75/F _06
1~93~
without pressure an~ since the dehydrogenation ~ith reElux in
the preferred temperat~lre range proceeds most rapidly and wi-th
high selectivity.
The efficiency of the process is increased by vigorous
agitation of the reaction mixture as long as it is in contact
with the catalyst.
It is very advantageous -to operate in the presence of
hydrogen accepting substances, that is, substances which bind
the hydrogen immediately after its formation, thus cnsuring
that the dehydrogena-tion reaction proceeds under relatively
gentle conditions. Suitable hydrogen accep-tors are unsaturated
compounds such as styrene, ~- and ~-methylstyrene, s-tilhene,
anthracene, acenaphthylene, crotonic acid, maleic acid, fumaric
and cinnamic acid as well as the alkyl esters of these acids
with alcohols having up to 6 car~on atoms/ butene-diol, butine-
diol and thir acetates and propionates, mesityl oxide, benzal-
acetone or maleic acid anhydride. Also nitro compounds, for
example nitrobenzene, p-nitrotoluene or o-nitrophenol are appro-
priate.
The process of the invention is generally carried out in
the presence of a fixed bed catalyst or a catalyst being main-
: tained in suspension in the reaction solution by vigorous agi-
- tation.
In the case of using a fixed bed catalyst, the particle
25~ size of the catal~st is advantageously from 0.5 to 10 mm, pre-
ferably from 2 to 5 mm.
In the case where a`catalyst on a carrier suspended in the
reaction. medium i9 used, a particle size of the catalyst of
~:~ from O.Ol to 5 mm, preferably from 0.05 to 1 mm, is recommended.
- 6 -
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06
10~930~
Depending on the nature of the liquid and the catalyst, the
suspension ~ontains generally from 0.~ to 40 parts by weight
o~ catalyst on carrier per 100 parts by weight o~ the l~quid.
A ratio of from 1 to 30 parts by weight of catalyst on carrier
pe~ 100 p~rts by weight ~ s~l~rPnt ~s pre~P red.
When the process is carried out in the gaseous phase, a
carrier gas such as nitrogen, C02, or hydrogen or a hydrogen
acceptor such as ethylene or propylene, or highly volatile
æolvents, ~or example alcohols, ethers, acetic acid or acetone~
ma~ be added to the starting material be~ore the vaporization.
Water is mo~t advantageous, slnce it~ presence increases con-
siderably the se~tivity of 2-hydroxy-naphthalene ~ormation~
be~ause it prevents ~ormation of naphthalene~
In the liquid as well as in the gaseous phase~ the ternper-
ature and the residence time necessary for dehydrogenation may
vary within a wide range, depending on the starting materials
and ~he kind o~ cntalyst used. Generally~ operations are
carried out at temperatures of ~rom 160 to 450C, preferably
~rom 200 to 350C, continuously or batchwise, under reduced or
normal pressure, although higher pressures are allowed~ for
example 20 atmospheres~ on condition that the H2 partial pres--
sure is kept low.
The following exampl~s illustrate the in~ention.
E X A M P L E S:
m e starting materials for Examples 1 to 5 have been pre-
pared according to the method described ln Organic Syntheses,
; Vol. 459 pp. 130 - 83, and identified according ko the data in-
, ~
dicated by ~.L. Augustine et al. in Chem. Ind. (London~, 1963
29 pp. 490j491.
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HOE 75~ 006
~ 3
E X A M P L E 1:
In a three~-necked flask having a capacity o~ 100 ml and
provided with thermometer, reflux condenser and gas colleotor
vessel, 50 ml of diethyleneglyool diethyl ether, 1 g of de-
hydrogenation catalyst (0.1 g Pd on 0.9 g active carbon and
4.8 g (0.032 mol) of a mixture composed of about 80 % of
(9~-octalone-27 10 % of~9 (1)-octalone-2 an~ 10 % of
9-hydroxydecalone-2 were heated for 5 hours at 190C7 which
caused the development of 2.1 l o~ gasO A~ter suction~filtra-
tion of the catalyst~ the gas chromatography analysis o~ the
filtrate yielded 3.9 g o~ B-naphthol (85 mol %) and 0.5 g of
naphthalene (12 mol ~).
2.
4,8 g of the oxo-cycloaliphatic mixture o~ Example 1 and
1 g of Pd/C catalyst (0.1 g Pd, 0.~ g active carbon ) were
heated for 1 hour at 215 - 220C, which caused the development
of 2.0 l o~ gas. After cooling, the reaction mixture was
digested with ~0 ml of di-ethyleneglycol diethyl ether~ and
the catalyst was suction-filtered. The gas chromatography
analysis o~ the filtrate yielded 3.2 g of R-naphthol (70 % o~
the theoretical yield~ and O.g g of naphthalene (22 % of the
theoretical yieId)~
E X A M ,~ ~ B 3~
In a glass reactor having a diameter of 10 mm and a length
of 120 mm, there were 5 ml of catalyst (2.0 weight % o~ Pd on
active carbon~ bu~k density 005 g/ml, diameter 0~2~2 mm).
The catal~st temperature was maintained during the reaction
. j ,-
a~ ~0C by means o~ an electric stove. Before the reaction~
29 ~he catalyst had been actlvated ~or 2 hours at 170C b~ me~ns
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HOE 7~F 006
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of 0.7 l!h of N2 and 1.4 l/h of H2.
Subsequently, 2.25 g/h of the oxoc;ycloaliphatic mixture
described in Example 1, 0 7 l o~ N2 and 1.4 l o~ H2 per hour
were forwarded via an evaporator preheated to 350C to the
~boYs cata~yst haYl nv a tempera+l]re of 32QC, The prO~l~C+
collected at the reactor outlet in a cooled collector vessel
solidified in the form of white crystals (2.15 g/h3 having a
melting point of 106C, which crystals9 according to GLC
~ analysis,consisted o~ 60 % o~ B-naphthol and 35 % of naph~
thalene.
E X A M P L E 4:
The glass reactor described in Example 3 was charged with
the catalyst described in the same Example.
After a 2 hour activation by means of 0.7 l/h o~ N2 and
1.4 l/h of H2 at 170C, 1.9 ~/h of the oxo-cycloaliphatic
mixture as described in Example 1, and 1.4 1 of H2, 2~0 g of
H20 and 0 7 l o~ N2 (all per hour) were forwarded to the
catalyst ha~ing a temperature of 285C. The product obtained
in the cooled collector vessel was in ~he form of an aqueous
crystal pulp which, according to GLC analysis, contained 1.5 g
(~2 % o~ the theoretical yield)o~ ~-naphthol and 0.24 g
(15 ~ of the theore-tical yield ) of naphthalene.
_A~
0.5 g of 9-hydroxydecalone~2 (melting poi~t 145C) and
0.1 g of catal~Jst (0.01 g of Pd on 0.09 g o~ active carbon)
were heat~d ~or 20 minutes at 210C in a~ Erle~eye~ ~lask
having a capac$ty o~ 20 ml whereby gas development occurred-
~ A~te~ cooling, 10 ml~ of ethanol were added9 the catalyst was
29 separated by ~iltration9 and the filtrate was subjected to thin
_ g .,,
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IOE 75/ _006
~ 3~
layer chromatograph~ on sil:ica gel plates with an ether/hexane
1/1 mixture as solven-t, whereby ~-naphthol was de-tec-ted.
On spraying with a methanolic so].ution of fast blue salt ss
and subse~uent treating w:ith ammon:ia vapor, ~-naphthol was
showing as a violet spot having a Rf value of 0.51. Color and
Rf value are identical to color and Rf value of yenuine
~-naphthol.
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