Note: Descriptions are shown in the official language in which they were submitted.
128341~;
AN IMPROVED PROOESS FOR 'l~n~: PREPAR~TION OF
BICYCLIC AMIDE ACETALS
This invention relates to an improved process for the
preparation of bicyclic amide acetals by the reaction of an
organic nitrile with a dialkanol amine wherein the reaction
temperature is maintained below about 140 degrees C. and the
bicyclic amide acetal is removed from the reaction mixture by
extraction in a hydrocarbon solvent.
The synthesis of bicyclic amide acetals by the reaction
of a dialkanol amine, such as diethanol amine with alkyl
nitriles has been reported to result in relatively low yields
(30-40%) in Agnew_Chem. 85, Patenk Publication No. 2,344,607.
Reaction temperatures used in this synthesis have been in the
range of 120 to 180C. The preparation and reactions of
bicyclic amide acetals are also described in Synthesis, (1~71),
pp. 16-26.
Although low yield synthesis of bicyclic amide acetals
by the reaction of dialkanol amines and nitriles at 120 to 180
degrees C., usually in the presence of a catalyst such as an
alkali metal, has been described, no reaction between the
dialkanol amine and the bicyclic amide acetal at these
temperatures has been disclosed. Because all of the bicyclic
amide acetals boil at temperatures greater than 170 degrees C.
under ambient pressure, and at these temperatures the dialkanol
amine reacts with the bicyclic amide acetal, lower yields in
the prior art process were inevitable. The use of solvent
extraction to separate the bicyclic amide acetal from the
reaction mixture to produce significantly higher yields has not
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previously been disclosed or suggested. The extraction solvent
can be any inert solvent and can even include an excess of the
_ starting nitrile itself.
The bicyclic amide acetals produced by the improved
process of this invention include those having the Formula I
~"
~..
, P
~1: ~
/
I
wherein n is 1 or 2, R and R~ independently represent hydrogen,
an alkyl group containing from 1 to 10 carbon atoms or an aryl
group containing from 6 to 12 carbon atoms, and when n is 1, R'
represents an alkyl group containing from 1 to 20 carbon atoms,
an aryl group containing from 6 to 12 carbon atom~, or an
alkaryl group containing from 7 to 20 carbon atoms, and when n
is 2, R' represents an al~ylene group containing from 1 to 18
carbon atoms, an arylene group containing from 6 to 14 carbon
atoms or an alkarylene group containing from 7 to 20 carbon
~oms .
We have discovered that higher yields of purified
bioyclic amide acetals can be obtained by separating the
bicyclic amide acetal via solvent extraction prior to any
distillation of the bicyclic amide acetal. Thu~, following the
reaction of diethanol amine with an alkyl nitrile at a reaction
betwe~n room temperature and 140-C. The reaction mixture in
our process is subjected to extraction at about room
- 2
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temperature to isola'ce the bicyclic amide acetal product. The
preferred solvents for the extraction of bicyclic amide acetal
from the reaction mixture are hydrocarbons and hydro~arbon
ethers containing from 2 to 20 carbon atoms and most preferred
are aliphatic hydrocarbons such as pentane, hexane, heptane,
petroleum ether and aromatic hydrocarbons such as benzene and
toluene. The starting nitriles themselves can also be used as
extraction solvents in our invention. In the extraction the
bicyclic amide acetals selectively go into the solvent layer
and dialkanol amine and catalyst as well as high boiling
byproducts remain in the remainder of the reaction mixture.
The extracted bicyclic amide acetal, along with the nitrile and
solvent can then be sub~ected to fractional distillation at any
desired temperature without loss of yield. The use of an
excess amount of the nitrile often obviates the necessity for
any other solvent. The nitrile containing the bicyclic amide
acetal separates and can be isolated readily from the remainder
of the reaction mixture.
The organic nitriles useful in this process include
aliphatic mononitriles having from 1 to 20 carbon atoms,
aromatlc mononitriles having from 7 to 15 carbon atoms and
alkylaromatic mononitriles having from 8 to 20 carbon atoms and
aliphatic dinitriles having from 3 to 22 carbon atoms,
aromatic dinitriles having from 8 to 16 carbon atoms and
alkaryl dinitriles having from 9 to 21 carbon atoms.
The dialkanol amines useful in the process of this
invention include substituted and unsubstituted dialkanol
amines having the general formula HOC(R)2CH2NHCH2C(R")20H
wherein R and R" have the foregoing designations.
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The process of this invention is further illustrated in
the following representative examples.
EXAMPLE 1
Diethanol amine (0.26g) and a bicyclic amide acetal of
Formula I wherein n is 1, R and R" are hydrogen and R' is
benzyl (0.51~ were mixed and heated in a closed mini reactor
with constant stirring at 160C. for 2 1/2 hours. GLC analysis
of the mixture showed that 47% of the diethanol amine and about
55% of the bicyclic amide acetal had reacted (were no longer
present).
~XAMPLE 2
Diethanol amine (1.08g) and a bicyclic amide acetal of
Formula I where n is 1, R and R" are hydrogen and R' is methyl
(1.3g) were mixed in a mini reactor and heated at 120C. for
thrse hours, followed by heating at 150C. for two hours. GLC
analysis of the mixture indicated that about 20% by weight of
the starting diethanol amine and 25% of the bicyclic amide
acetal had reacted.
EXAMPLE 3
Diethanol amine (1.05g) and the bicyclic amide acetal of
Formula I in which n is 1, R and R" are hydrogen and Rl' is
methyl (1.25g) were mixed and heated at 120C for three hours.
GLC analysis showed the consumption of only about 2% by weight
of each reactant.
XANPL~ 4
The procedure of the pxior art (German Patent
Publication No. 1,344,~07) was followed using 117.15g of benzyl
nitrile and 105.14g of diethanol amine. The reaction was
carried out at 140C. for about 20 hours. The GLC analysis of
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the reaction mixture indicat~d the presence OI about 6
by weight of the product of Formula I wherein n is 1, R
and R" are hydrogen and R' is benzyl and about
10~ by weight of benzyl nitrile and
4% of diethanol amine. The reaction mixture was
subjected to fractional distillation under reduced
pressure. Because of the high boiling nature of the
product, the pot temperature had to be increased about
150C. in order to distill the product at 110-20C.
10 /Or 6-2 mm Hg pressure which afforded a 41% overall
yield of the bicyclic amide acetal. The pot residue
~95g, 43%) was found to contain only traces o~ the
product bicyclic amide acetal and was highly viscous
indicating higher molecular weight byproducts. This
shows that about 14% by weight of the bicyclic amide
acetal product was lost during the isolation by
distillation.
EXAMPLE S
Diethanol amine (25.6g) containing 2 mole percent
of sodium and benzonitrile (25g) were mixed and heated
at 100C. for 56 hours under nitrogen. The GLC
analysis of the reaction mixture indicated the
formation of about 3B% by weight of bicyclic amide
acetal of Formula I wherein n is 1, R is 1, R and R"
are hydrogen and R' is phenyl. The reaction mixture
was brought back to room temperature and the product
and the unreacted benzonitrile were separated from
diethanol ami~e and the catalyst by extr~ction with
three 40 ml portions of hexane and 20 ml of toluene.
GLC analysis of the com~ined extracts showed them to
contain mainly the nitrile and the bicyclic amide
acetal product with only traces ~less than 1~) of
diethanol amine, whereas the residue was found ts be
mainly diethanol amine with traces (1 to 2%) of
bicyclic amide ace~al and nitrile. The solvent was
removed from the extract and the rPsidue was
fractionally distilled gi~ing a 35% yield of the
bicyclic amide acetal (78-79~C./0.02 mm Hg~. This
,
lZ~334~;
experiment demonstrates that essentially no loss of
product occurs when separation of product ~y extraction
is carried out prior to the distillation step which
precludes possible reaction between the bicyclic amide
acetal and diethanol amine.
EXAMPLE 6
The procedure of Example 5 was repeated using
52,7g of diethanol amine with 2 mole percent of sodium
and 90.7g of undecyl nitrile. GLC analysis of the
reaction mixture after 72 hours of reaction at 100~ C.
showed the formation of about 42% of the bicyclic ~mide
acetal of Eormula I in which n is 1, R and ~ are
hydrogen and R' is undecyl. The extraction with
pentane (three 50 ml portions) and fractional
distillation of the extract afforded about 52g (greater
than 3~% yield) of the bicyclic amide acetal product.
EXAMPLE 7
A 40g mixture containing approximately 50% by
weight of diethanol amine, 45% of a bicyclic amide
acetal of Formula I wherein n is 1~ R and R" are
hydrogen and R" is methyl and 5% of acetonitrile w~s
extracted with three 80 ml por~ions of pentane at room
~5 temperature. The extracts were combined and analyzed
and it was found that 95% of the total bicyclic amide
acetal had been extracted. The GLC analysis of the
residue not extracted showed thP presence mainly of
diethanol amine with about 5% of the bicyclic ~mide
acetal.
EXA~PLE 8
A mixture of 20% by weight of the bicyclic amide
acetal of Example 7 and 80% of diethanol amine. The
bicyclic amide acetal was separated by extraction using
acetonitrile as the solvent as in Example 7, GLC
.
',,~ ,~,0
~;283~5
analysis of the residue left after extraction indicated
the presence of 95% of diethanol amine and about 5~ of
the bicyclic amide acetal.
EXAMPLE 9
Acetonitrile (83.8g, 2.04 mols) and
diethanol-amine (88.2g, 0.84 mol1 containing 2 mole% of
sodium (based on diethanol amine) as catalyst were
reacted for 30 hours at 79C. to produce the methyl
bicyclic amide acetal of Formula I wherein n is l, R
and R" are hydrogen and R' is methyl in 75% yield.
Separation of the bicyclic amide acetal product from
the unreacted starting material and catalyst was
accomplished with pentane solvent. The pentane
lS extracted 93.5% of the bicyclic amide and no diethanol
amine (GLC analysis). The mo~her liquor left after $he
extraction was found by GC to contain 100% of the
unreacted diethanol amine and only 6.5% of the bicyclic
amide acetal.
