Mf. Costa et al., Synthesis of chiral (7R)-[eta(6)-5-(N,N-dimethylamino)-7-formyl-1,3-benzodioxole]-chromium complex and its application in the synthesis of optically active cis-beta-lactams, J ORGMET CH, 632(1-2), 2001, pp. 27-40
Prochiral imine chromium complexes derived from the racemic (5-NN-dimetylam
ino-7-formyl-1,3-benzodioxole)chromium complex 4 and several amines reacted
with acetoxylketene, generated from its corresponding acid chloride and tr
iethylamine, to produce the corresponding beta -lactam complexes 6a, 6b and
6c with complete control of cis-diastereoselectivity. In a similar manner.
the imine condensation of the chiral imine complexes 11a and 11b. derived
from the chiral aldehyde complex 4I, not only provides complete cis-diaster
eoselection of the beta -lactam complexes 12a and 12b, but remarkable enant
ioselectivities as well. X-ray crystal structures of 4I and 12a were obtain
ed and the mechanics implications within the context of the general mode pr
oposed by several authors for the stereochemical outcome of the Staudinger
reaction are in agreement with these results. (C) 2001 Elsevier Science B.V
. All rights reserved.