Highly regio- and stereoselective asymmetric bromoazidation of chiral alpha,beta-unsaturated carboxylic acid derivatives: scope and limitations.
Lewis acid catalyzed asymmetric bromoazidation of chiral alpha,beta-unsaturated carboxylic acid derivatives was performed using N-bromosuccinimide (NBS) and trimethylsilyl azide (TMSN3) as the bromine and azide sources. Among the Lewis acids, Yb(OTf)3 was found to be the best catalyst. Regio- and anti-selectivity of 100% and moderate to good diastereoselectivity (up to 89:11) with good yields were obtained when Oppolzer's bornane sultam chiral auxilairy was used. Diastereoselectivity of >95:05 was observed when (2S,5S)-2,5-diphenylpyrrolidine was used as the chiral auxiliary.
Hajra
Saumen
S
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India. shajra@chem.iitkgp.ernet.in
Bhowmick
Manishabrata
M
Sinha
Debarshi
D