Stereochemical Aspects of Aldehyde Additions to Cyclohex-2-Enylstannanes

Abstract

Cyclohex-2-enylation of aldehydes, mediated with boron trifluoride etherate, involves γ-equatorial approach of the presumed aldehyde-Lewis acid adduct (RCHO-BF₃), irrespective of starting stannane stereochemistry. Marginal threo selectivity characterizes homoallyl alcohol formation from benzaldehyde, whereas alkanals react with high erythro selectivity, so that 1-(1′-hydroxyalkyl)cyclohex-2-enes in this diastereomeric form are available based on allyltin chemistry.