Regio- and stereoselective cyclopropanation of functionalised dienes. Novel methodology for the synthesis of vinyl- and divinyl-cyclopropanes

Dienes, bearing an electron-withdrawing substituent at C-1, are cyclopropanated regio- and stereoselectively at the CC double bond proximal to this electron-withdrawing group. The highest selectivity is observed in the case of dienylboronates. The cyclopropanation of these substrates affords almost exclusively the synthetically useful 1-boronato-2-vinyl-cyclopropanes.