Preparation of N-alkoxycarbonyl-substituted cyclic lactams and ketones

N-alkoxycarbonyl-substituted cyclic lactams and nitrogen-containing cyclic ketones are prepared by reaction of a C.sub.1-20 alkyl ester of trichloroacetic acid with the corresponding cyclic lactam or nitrogen-containing cyclic ketone.

BACKGROUND OF THE INVENTION 
This invention relates to a novel process for preparing 
N-alkoxycarbonyl-substituted cyclic lactams and ketones by the reaction of 
an alkyl ester of trichloroacetic acid with the corresponding cyclic 
lactam or nitrogen-containing cyclic ketone. The products are useful as 
intermediates in the synthesis of isocyanates and the preparation of other 
useful chemicals. 
It is previously known to react ethyl chloroformate with 2-oxazolidinone in 
the presence of an equivalent amount of triethylamine. Y. A. Naumov et 
al., Khim. Geterotsikl. Soedin., 768 (1976) (Chem. Abs., 85, 123067q 
1976). The process is not preferred for commercial implementation due to 
the unavoidable formation of large amounts of salt during the process 
according to the following equation. 
##STR1## 
Therefore an alternate procedure to useful chemical intermediates such as 
this is desirable. 
SUMMARY OF THE INVENTION 
A novel process has now been discovered for the preparation of 
N-alkoxycarbonyl-substituted cyclic lactams and ketones represented by the 
formula: 
##STR2## 
where X is oxygen or methylene, R' is C.sub.2-4 alkylene and R is 
C.sub.1-20 alkyl, which comprises reacting a C.sub.1-20 alkyl ester of 
trichloroacetic acid with a cyclic lactam or nitrogen-containing cyclic 
ketone of the formula: 
##STR3## 
where X, R' and R are as previously defined. Preferred ester reactants are 
C.sub.1-4 alkyl esters of trichloroacetic acid. Most preferred is ethyl 
trichloroacetate. Preferred cyclic lactam or nitrogen-containing cyclic 
ketone reactants include 2-oxazolidinone, 2-pyrrolidinone or caprolactam. 
Most preferred is 2-oxazolidinone. 
The by-product, chloroform, is easily separated from the desired cyclic 
ester derivative and is itself commercially valuable. 
DETAILED DESCRIPTION OF THE INVENTION 
The reaction is conducted by contacting the desired reactants at an 
elevated temperature preferably in the presence of a suitable acylation 
catalyst. The reaction is suitably conducted in reaction vessels of 
ordinary design and construction. Temperatures from about 100.degree. C. 
to about 160.degree. C. are suitable. Preferred temperatures are from 
about 105.degree. C.-125.degree. C. 
A preferred acylation catalyst is 4-dimethylaminopyridine. The catalyst is 
added in a catalytically effective amount from about 0.01 percent to about 
10 percent by weight. 
Elevated pressures may be employed if desired, however, no advantage is 
known to arise therefrom. Suitable reaction rates are obtained without the 
use of superatmospheric pressure. 
Molar ratios of cyclic lactam or nitrogen-containing cyclic ketone to 
trichloroacetic acid ester of from about 1:1 to about 1:30 may suitably be 
employed. Preferably an excess of the C.sub.1-20 alkyl ester of 
trichloroacetic acid is employed. 
Reaction times may vary from a few minutes to several hours, depending on 
the temperature of the reaction and the alkyl ester employed. Separation 
of the product is easily accomplished by ordinary techniques such as 
distillation.

SPECIFIC EMBODIMENTS 
Having described my invention, the following examples are provided as 
further illustrative of the present invention. 
EXAMPLE 1 
Preparation of 3-Carboethoxy-2-Oxazolidinone 
A mixture of 2-oxazolidinone (9.0 g, 0.10 mole) and 25 ml (0.18 mole) of 
ethyl trichloroacetate were heated to 120.degree. C. in an oil bath. A 
small amount (ca 50 mg) of 4-dimethylaminopyridine was added to the 
stirred solution, during which time vigorous reflux began. After removing 
most of the chloroform by a Dean-Stark trap, the dark solution was allowed 
to cool to room temperature. Bulb to bulb distillation at 105.degree. 
C.-120.degree. C. (0.05 mm) yielded 14.1 g (0.0887 mole, 89 percent yield) 
of the product as a clear liquid which solidified to a colorless solid (mp 
40.degree. C.-44.degree. C.) on standing at room temperature. Spectral 
data confirmed its structure. 
EXAMPLE 2 
Preparation of N-Carboethoxy-2-Pyrrolidinone 
In a manner similar to the above procedure, a solution of 2-pyrrolidinone 
(9.1 g, 0.11 mole), ethyl trichloroacetate (140 ml, 2.9 mole) and 
catalytic amounts of 4-dimethylaminopyridine were reacted together for 1 
hour. Distillation at 90.degree. C.-95.degree. C. (0.4 mm) afforded 14.2 g 
(0.094 mole, 82 percent yield) of the product as a clear liquid. Spectral 
data confirmed its structure.