Chemistry Reference
In-Depth Information
by conversion of the bis(chloroformate) derivative to the desired dicarbamate by
ammoniation with gaseous NH
3
. Antipyrine gave consistently higher yields than
other tertiary amines [382].
Typical procedure. 2,2-Diethyl-1,3-propanediol dicarbamate [382]:
To a stirred solution
of phosgene (20 g, 0.2 mol) (for a safe source, see Chapter 7) in toluene (200 mL) at
10
C, a cooled solution of 2,2-diethyl-1,3-propanediol (13.2 g, 0.1 mol) and anti-
pyrine (38 g, 0.2 mol) in chloroform (100 mL) was added at such a rate that the
temperature of the reaction mixture was maintained at
5to0
C. The mixture
was then allowed to warm slowly to room temperature and was left at this tem-
perature overnight. The antipyrine hydrochloride formed was removed by filtration
and the bis(chloroformate) was converted directly to the carbamate by treating the
filtrate with gaseous ammonia with moderate cooling. The carbamate was sepa-
rated by filtration, freed from ammonium chloride by extracting with 250 mL
of cold water, and recrystallized from hot water; 17.5 g (80%) of 2,2-diethyl-1,3-
propanediol dicarbamate was obtained.
Monocarbamate derivatives of 1,3-propanediol may be prepared in a similar
manner, using an equimolar ratio of phosgene and diol, but this reaction yields,
in addition to the desired monocarbamate derivative, a considerable amount of
unreacted diol and appreciable quantities of the dicarbamate and cyclic carbonate
derivatives. The di
culty of separating these products may be avoided by forming
the monocarbamates through ammonolysis of the cyclic carbonate esters (yields of
53-75% are obtained) [382]. The latter compounds are prepared by the reaction of
equimolar quantities of phosgene and propanediol in the presence of antipyrine at
a temperature somewhat higher than that found most suitable for chloroformate
formation.
O
Cl
OH
COCl
2
Toluene
HC
HC
O
529
530
N
O
R
H
2
NR
Toluene
HC
O
531
R
= CH
2
CH
2
OH, CH
2
COOEt, CH
2
CONH
2
,
H
2
COC
N
OEt
H
2
C
