Triflic Acid-Catalyzed Additions of 2-Alkoxycarbonyl Allylboronatesto Aldehydes. Study of Scope and Mechanistic Investigation of theReaction Stereochemistry
The substrate scope and the effect of substrate on the observed inversion of stereoselectivity in the triflicacid-catalyzed allylboration reaction between 2-alkoxycarbonyl allylboronates and aldehydes are presented.A mechanistic investigation is described so as to confirm the involvement of a carbocation intermediateas the source of stereochemical inversion. This methodology allows a facile access to β,γ-disubstitutedfive-membered ring lactones with an exo-methylene at the α-position.