Control of stereochemistry: a general synthesis of cis- or trans-beta,gamma-disubstituted-gamma-butyrolactones following Z-crotylboration.
[reaction; see text] A general and practical procedure for the highly diastereoselective preparation of either the cis- or trans-beta,gamma-disubstituted-gamma-butyrolactones by appropriate choice of Lewis or Bronsted acid catalysts during crotylboration or lactonization is reported. The cis-stereochemistry of the Z-crotylboration product can be inverted with strong acids during lactonization. A carbocation mechanism and catalytic cycle has been proposed.
Ramachandran
P Veeraraghavan
PV
Herbert C. Brown Center for Borane Research, Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA. chandran@purdue.edu
Pratihar
Debarshi
D
Biswas
Debanjan
D