1,5-Stereocontrol in Bismuth-Mediated Reactions between Aldehydes and Allyl Bromides: Stereoselective Synthesis of Open-Chain all-syn- and anti, anti-1,3,5-Disposed Trimethylalkanes

Abstract

LETTER 575 1,5-Stereocontrol in Bismuth-Mediated Reactions between Aldehydes and Allyl Bromides: Stereoselective Synthesis of Open-Chain all-syn-and anti, anti-1,3,5-Disposed Trimethylalkanes , 5 -S t e r e o c o n t r o l i n B i s m u t h -M e d i a t e d R e a c t i o n s b e t w e e n A l d e h y d e s a n d A l l y l B r o m i d e sAbstract: The reaction of 5-benzyloxy-2,4-dimethylpent-2-enyl bromide with the bismuth species generated by reduction of bismuth(III) iodide by zinc powder gives an intermediate which reacts with aldehydes with useful levels of stereocontrol in favour of 1,5-anti-(3E)-5-methylalk-3-enols. Manipulation of protecting groups, stereoselective hydrogenation, and tosylate displacement using a higher-order cyanomethylcuprate leads to either all-syn or anti,anti-1,3,5-disposed trimethylalkanes.