Chemistry Reference
In-Depth Information
Miscellaneous reagents
A series of 2-isocyanatoacyl chlorides 1231 was prepared by treating glycine 1226, dl-
alanine, l-valine, l-leucine, and l-phenylalanine with phosgene in an inert solvent
such as dioxane. The acid chloride group of the 2-isocyanatoacyl chloride is more
reactive as an electrophile than the isocyanate group. In reactions with an equi-
molecular amount of ethanol or water, 2-isocyanatoacetyl chloride 1231 gives ethyl
2-isocyanatoacetate and 2,5-oxazolidinedione, respectively. With a molar excess of
p-phenetidine, it gives 3-(p-phenethyl)hydantoin, while with a 2 molar or greater
excess of amine it gives the corresponding ureidoamide. Treatment with an equi-
molar amount of N-methylaniline in the presence of an equimolar amount of pyr-
idine furnished N-methyl-2-isocyanatoacetanilide [447].
O
COCl
2
-HCI
H
2
N
H
Cl
H
COOH
1226
1227
O
2 HCI
Cl
HCl * H
2
N
O
HN
-HCl
O
O
1228
1229
-2 HCI
COCl
2
O
Cl
Cl
Cl
H
O
C
N
-HCI
O
O
1231
1230
Typical procedure. 2,5-Oxazolidinedione 1228 [447]:
Phosgene (for a safe source, see
Chapter 7) was passed in a fine stream into a suspension of finely ground glycine
(15 g) in dry dioxane (750 mL) at 45-50
C with e
cient agitation. A clear solu-
tion was obtained after 5 h. This solution was filtered to remove unreacted glycine
(1.7 g), and the dioxane was then removed under reduced pressure at a tempera-
ture below 40
C under exclusion of moisture. The residue was treated with dry
diethyl ether (100 mL), and the crystals of 2,5-oxazolidinedione 1228 were collected
by filtration and dried over P
2
O
5
in a vacuum desiccator. The crude product thus
obtained, 16 g (89%), was recrystallized from ethyl acetate/petroleum ether to yield
14.3 g (77.2%) of pure material, which showed no melting point because of poly-
merization.
