Chemistry Reference
In-Depth Information
Typical procedure. Se-Methyl-N-phenylselenocarbamate 664 [446]:
Phenyl isocyanate
661 (R
Ph) (0.11 mL, 1.0 mmol) was added to a solution of LiAlHSeH 662 (1.0
mmol) in THF (10 mL). The reaction mixture was stirred at room temperature for
1 h. Methyl iodide 663 (0.06 mL, 1.0 mmol) was then added, and the reaction
mixture was stirred at room temperature for 2 h. It was then extracted with diethyl
ether and the combined extracts were washed with water. The organic phase was
dried over sodium sulfate and concentrated to dryness. The residue was purified by
flash chromatography on silica gel eluting with dichloromethane/n-hexane (4:1) to
give Se-methyl-N-phenylselenocarbamate 664 (0.15 g, 70%) as yellow crystals; mp
90.8-93.0
C.
A series of 2-isocyanatoacyl chlorides of type 670 was prepared by treating glycine,
DL
-alanine,
L
-valine,
L
-leucine, and
L
-phenylalanine with phosgene in an inert solvent
such as dioxane [447].
ΒΌ
O
O
COCl
2
2 HCI
Cl
HCl * H
2
N
O
H
2
N
COOH
Cl
H
COOH
HN
-HCl
-HCI
O
O
665
666
667
668
-2 HCI
COCl
2
O
Cl
Cl
O
C
N
Cl
H
-HCI
O
O
670
669
The acid chloride group of the 2-isocyanatoacyl chloride 670 is more reactive as an
electrophile than the isocyanate group (see Section 4.3.5. ''Reactions with Binu-
cleophiles''). For example, in reactions with equimolecular amounts of ethanol and
water, 2-isocyanatoacetyl chloride 670 gave ethyl 2-isocyanatoacetate and 2,5-oxazo-
lidinedione, respectively. With a molar excess of p-phenetidine, it gave 3-(p-phene-
thyl)hydantoin, and with a 2 molar or greater excess of amine it gave the corre-
sponding ureidoamide. Treatment with molar quantities of N-methylaniline in the
presence of molar quantities of pyridine furnished N-methyl-2-isocyanatoacetanilide
[447].
Typical procedure. 2,5-Oxazolidinedione 667 [447]: Into a suspension of finely
ground glycine (15 g) in dry dioxane (750 mL), phosgene (for a safe source, see
Chapter 7) was introduced in a fine stream at 45-50
C with e
cient agitation. A
clear solution was obtained after 5 h. This solution was filtered to remove un-
reacted glycine (1.7 g), and the dioxane was then removed under reduced pressure
at a temperature below 40
C with protection from moisture. The residue was
