Regioselective preparation of tetrasubstituted alkenes from ketones using Krief`methodology as a key step for a straightforward synthesis of dienynes

Abstract

Dedicated to Professor Alain Krief on the occasion of his 65th birthday and retirement AbstractDienynes 2a-c bearing a silylated substituent (SitBuMe 2 , SiMe 2 Ph, Si(iPr) 3 ) at the terminal position of the 1,3-butadiene moiety are highly valuable compounds as they constitute the north part of polyunsaturated precursors to the taxane framework that we have reached through [2+2+2]/[4+2] cyclization strategies. They have been efficiently prepared over ten steps from the corresponding trialkylsilylchlorosilanes, the crucial step of these syntheses being the olefination of a ketone that was eventually successful via selenoacetals.