Sulfone directed alkylative bridge cleavage of oxabicyclic vinyl sulfones with organolithium reagents (1)

Abstract

An efficient regio- and stereocontrolled methodology for the alkylative bridge cleavage of oxabicyclic vinyl sulfones is described. A range of 7 -oxabicyclic[2.2.1. ]heptenyl and 8-oxabicyclic [3.2.1.]octenyl sulfones has been found to undergo an overall syn S~' opening when treated with a wide variety of organolithium reagents and lithium aluminum hydride. In this manner, higWy functionalized cyclohexenyl and cycloheptenyl sulfones, versatile synthetic intermediates, are now available in high yields. The complete stereoselectivity encountered in the exo conjugate addition may be explained by chelation of the organometallic reagent with the oxygen bridge and steric factors. Furthermore, less-strained substrates allow for complete control of the addition and elimination stages.

Se describe una interesante rotura alquilante regio-y estereocontrolada del puente de oxabiciclo vinil sulfonas. Las 7-oxabiciclo[2.2.1] heptenil y 8-oxabiciclo [3.2.1.] octenil sulfonas sufren aperturas syn S~' cuando se tratan con una amplia variedad de reactivos organolíticos e hiduro de litio y aluminio. De esta forma, se obtienen ciclohexenil y cicloheptenil sulfonas, altamente funcionalizadas, que son intermedios sintéticos versátiles. La completa estereoselectividad encontrada en la adición conjugada exo puede explicarse en base a la quelación del reactivo organometálico con el oxígeno puente.