Chemistry Reference
In-Depth Information
0
C within 30 min to give carbamate 590. Subsequent addition of cyclopropyl-
methylamine in the same solvent and in the presence of NaHCO
3
gives the amino
acid urea derivative 591 in 92% yield.
The reaction proceeds under very mild conditions owing to the good leaving
group ability of the p-nitrophenyl moiety and hence is not applicable to the tetra-
substituted urea [417].
SMe
SMe
NO
2
4-NO
2
-C
6
H
4
OCOCl
O
589
BnO
H
BnO
N
N
O
MeCN, 0 °C
O
H
588
O
H
590
NHMe
MeCN, NaHCO
3
SMe
O
BnO
Me
N
N
O
H
92 %
591
Diphosgene
2-Oxazolidinones 593, which represent potential chiral auxiliaries, have been pre-
pared with diphosgene (trichloromethyl chloroformate) [418, 419].
R
1
R
2
Ph
R
1
R
2
HO
CCl
3
OCOCl
O
O
Et
3
N, CH
2
Cl
2
H
H
2
N
Ph
592
593
a : R
1
= Ph, R
2
= H
b : R
1
= R
2
= H
c : R
1
= R
2
= Ph
Typical procedures. (4R,5S)-4,5-Diphenyl-2-oxazolidinone 593a. [418]:
To a stirred
suspension of commercially available 592a (10.0 g, 47 mmol) and triethylamine
(14.4 mL, 0.10 mol) in dichloromethane (100 mL), diphosgene (3.0 mL, 25 mmol)
was added dropwise at 0
C and the mixture was stirred for 1 h at the same tem-
perature. After concentration in vacuo, the residue was poured into water to pre-
cipitate crystals. The crystals were collected by filtration, successively washed with
