Note: Descriptions are shown in the official language in which they were submitted.
HOE 73/F_299
lU4;~;~5z
The addition of reactive methylene groups to especially
activated C,C-double bonds in the presence of basic catalysts
is already known. 5-Oxo-carboxylic acid nitriles may be
prepared according to this reaction, known as Michael's
S addition, by adding ketones having one or several activated
hydrogen atoms in O<-position to the especially activated
double bond of the acrylonitrile.
5-Oxo-carboxylic acid nitriles may be transformed into
5-oxo-carboxylic acids by hydrolysing them with strong acids,
the acids obtained being valuable intermediate products for
preparing resorcins and plastics.
This process for preparing 5-oxo-carboxylic acids has the
disadvantage that it must be effected in two steps and that
ammonium salts are necessarily obtained in the hydrolysis of
the nitriles, considerably charging the waste waters.
It could not be expected that ketones could be directly
added to the considerably less active double bond of the
acrylic acid.
A process has now been found for preparing 5-oxo-carb-
oxylic acids of the formula
R2 IR4 15
Rl - C - C - CH - CH - COOH
O R3
wherein Rl-R5 are identical or di ~erent and each may represent
alkyl, cycloalkyl, aryl or aralkyl radicals or, with the
exception of Rl, hyrdogen and wherein Rl and R2 or R4 and R5
~ay form a 5- to 12-membered carbocyclic ring together with
the C-C group substituted by them, by reacting ketones of the
formula
- 2 -
HOE 73/F 299
~43;~52 ~
l2
Rl - C - CH
o R3
wherein Rl, R2 and R3 have the above meaning, with an acrylic
acid of the formula
14 15
HC = C - COOH
wherein R4 and R5 are defined as above, which comprises
carrying out the reaction in the presence of at least one
member of the group of ammonia, primary amines, primary
aliphatic amino-alcohols, aliphatic amino-carboxylic acids
having a primary amino group and Schiff's bases as catalysts.
Examples for the radicals Rl - R5 to be used in the
process according to the invention are straight-chained,
ramified or cyclic alkyl groups having up to 12, preferably
up to 6 carbon atoms, which may be substituted by the phenyl
or naphthyl radical. Furthermore Rl - R5 may be aromatic
radicals, having up to 14 carbon atoms, preferably the phenyl
or naphthyl radical, which may also be substituted, for
example, by alkyl, hydroxyl, halogen, alkoxy, cyano and nitro
groups. The process can be carried out with or without
solvents. Suitable solvents are, for example, acetonitrile,
tetrahydrofuran, benzene.
- 5-Oxo-carboxylic acids may be obtained, consequently, in
a one-stage reaction, according to this process, without
yeilding ammonium salts.
The following amines, amino-alcohols, amino-carboxylic
acids and Schiff's bases are examples of the catalysts
suitable for the reaction:
-- 3 --
_OE 73/F 299
1~)43352
methylamine, ethylamine, n-propylamine, isopropylamine,
n-butylamine, isobutylamine, secondary butylamine, tertiary
butylamine, amylamine, isoamylamine, ethylidenediamine,
tetramethylenediamine, hexamethylenediamine, cyclopentylamine,
cyclohexylamine, benzylaminer aminoethanol, glycocoll, B-
amino-propionic acid, -amino-caproic acid or the Schiff's
bases of the aforesaid amines, preferably those formed by the
ketones used.
Generally the quality of the catalysts to be used ranges
from 0.01 to 0.2 mol per mol of acrylic acid.
The following ketones, for example, may be used according
to the process of the invention: aliphatic ketones such as
acetone, methyl ethyl ketone, methyl propyl ketone, diethyl
ketone, methyl isopropyl ketone, methyl-t-butyl-ketone, 2-
hexanone, 2-heptanone, 2-octanone, 2-nonanone, acetyl-acetone,
acetonyl acetone, cycloaliphatic ketones such as cyclopenta-
none, cyclohexanone, l-methyl-2-cyclohexanone, acetophenone,
propiophenone and benzyl methyl ketone.
The following acrylic acids, for example, are suitable
for the reaction: acrylic acid, methacrylic acid, crotonic
acid, ~-methylcrotonic acid, cinnamic acid.
The molar proportion of ketone to acrylic acid may vary
within wide limits: it generally ranges from 2 : 1 to 20 : 1,
preferably 3 : 1 to 8 : 1.
The reaction can be effected within wide temperature
limits. Temperatures from 150 to 230C are the most suitable
to assure a good yield and a sufficiently quick reaction.
The pressure is not a critical factor, but the reaction
generally is effected at pressures ranging from atmospheric
-- 4
1~4~35Z 1~ 73/F 299
pressure to 50 atmospheres gauge. If the reaction is carried
out in the liquid phase, the process is preferably preferred
at the vapor pressure corresponding to the reaction tempera-
ture. It is also possible to operate in the gaseous phase.
The acrylic acid used may be reacted completely or
partially. Preferably the reaction rate should not surpass
90%, since otherwise the extended reaction time and the
higher reaction temperatures necessary for a reaction rate
above 90% are susceptible to favour secondary reactions.
The fraction obtained in the separation of the reaction
products by distillation containing the non-reacted starting
material and the catalyst can be re-used for the reaction.
The following examples illustrate the invention.
E X A M P L E 1:
2.320 g (40 mols) of acetone, 576 g (8 mols) of acrylic
acid, 42 g (0.7 mol) of isoproylamine and 2 g of hydroquinone
are heated to 180C for two hours in a 5 liter autoclave
provided with a stirrer and cooled subsequently. The gas-
chromatographic analysis of the reaction product (2.920 g)
showed the following composition: 70.8~ by weight of
acetone, 14.6% by weight of 5-oxo-hexanoic acid, 8.2~ by
weight of acrylic acid. The conversion of the acrylic acid
was 58.4~ and of the acetone 10.9%.
The yield of 5-oxo-hexanoic acid, calculated on the
converted acrylic acid, was 70.2% and, calculated on the
converted acetone, 75.3~.
E X A M P L E 2:
720 g (10 mols) of methyl ethyl ketone, 144 g (2 mols)
of acrylic acid, 21 g (0.35 mol) of isopropyplamine and
-- 5 --
I~OE 73/F 299
lV4;~35Z ~
2 g of hydroquinone were heated to 185C for 1 hour in a 2
liter autoclave. The reaction product (890 g) had the fol-
lowing composition: 67.8% by weight of methyl ethyl ketone,
16.2% by weight of methyl-5-oxo-hexanoic acid, 4.0% by weight
of 5-oxo-heptanoic acid and 3.0% by weight of acrylic acid.
The reaction rate of the acrylic acid was 81.5% and of
the methyl ethyl ketone 16.2%. The yield of 4-methyl-5-oxo-
hexanoic acid, calculated on the reacted acrylic acid, was
62% and, calculated on the reacted methyl ethyl ketone,
60%. The yield of 5-oxo-heptanoic acid was 15.5%, calcu-
lated on the reacted acrylic acid and 15%, calculated on the
reacted methyl ethyl ketone.
