Vinylic Organoboranes. 9. A General Stereospecific Synthesis of (Z)- and (E)-Disubstituted Alkenes Via Organoboranes

Abstract

A general and stereospecific synthesis of (Z)-disubstituted alkenes using mono- and dihaloboranes is presented. The hydridation of dialkylhaloboranes in the presence of 1-alkynes provides the corresponding dialkylvinylboranes (1), representing the first general synthesis of such derivatives. Treatment with iodine in the presence of sodium methoxide induces the migration of one of the alkyl groups from boron to the adjacent carbon, followed by a rapid deiodoboronation to afford (Z)-disubstituted alkenes (2) in high yields. Similarly, the hydroboration of 1-alkynes with alkylbromoboranes (R1BHBr·SMe2, 4) followed by iodination in the presence of sodium methoxide in methanol affords (Z)-disubstituted alkenes (2) in good yields. Both procedures constitute a general one-pot synthesis of (Z)-disubstituted alkenes from an alkene and 1-alkyne. A simple synthesis of Muscalure (7), the sex pheromone of the housefly (Musca domestica), is achieved in good yields. An alternative general stereospecific synthesis of (Z)- and (E)-disubstituted alkenes based on alkenylboronic esters is also described. © 1988, American Chemical Society. All rights reserved.