Studies on the enantiospecific synthesis of valeranes : and cyclopentannulation of allyl alcohols

Abstract

A convenient and efficient procedure for the reductive deoxygenation of aryl aldehydes, ketones, ketals, and benzyl alcohols using ionic hydrogenation conditions employing sodium cyanoborohydride as the reducing agent and boron trifluoride diethyl etherate (BF?·OEt?) as the Lewis acid has been achieved. Both esters as well as acids were found to be inert, pointing to the chemoselectivity of the reaction conditions. In the process, new methodologies for the reductive removal of tetrahydropyranyl (THP) and p?methoxybenzyl (MPM) protecting groups of alcohols have also been developed. The new ionic hydrogenation combination was also found to be suitable for a highly chemoselective deoxygenation of ?,??unsaturated carbonyl compounds, allyl alcohols, and allylic acetates to the corresponding olefins. An application of this methodology in the total synthesis of (+)?valerane is described in the first chapter of this thesis