Pheromones via Organoboranes. 3. Vinylic Organoboranes. 10. Stereospecific Synthesis of (Z)- and (E)-6- and -7-Alken-1-ols via Boracyclanes

Article abstract of DOI:10.1021/jo00237a004

Treatment of B-(E)-1-alkenylborinanes, obtained via monohydroboration of 1-alkynes with borinane, with iodine in the presence of a base results in the migration of one end of the cycloalkyl chain from boron to the adjacent carbon, producing intermediates containing the seven-membered borepane moiety, which undergo rapid deiodoboronation to afford the (Z)-6-alkenyl-1-boronate esters.These boronate esters, upon oxidation, provide (Z)-6-alken-1-ols.The procedure is successfully extended to B-(E)-7-alkenylborepane derivatives to produce (Z)-7-alken-1-ols.The preparationof (E)-6- and -7-alken-1-ols has been carried out via borinane and borepane derivatives.Borinane, as prepared previously, hydroborates cleanly 1-bromo-1-alkynes to provide the B-((Z)-1-bromo-1-alkenyl)borinanes.Treatment of these boron intermediates with sodium methoxide results in the displacement of bromine by one end of the boracycloalkyl moiety, producing the corresponding vinylboranes containing the seven-membered borepane moiety.The intermediates, upon controlled protonolysis, followed by oxidation, afford the (E)-6-alken-1-ols.The methodology was extended to borepane derivatives to provide (E)-7-alken-1-ols.The above procedures constitute a simple, very convenient, stereospecific, and general one-pot synthesis of (Z)- and (E)-6- and -7-alken-1-ols.The methodology has been applied to the synthesis of representative pheromones containing a (Z)- or an (E)-alkene moiety in good yields.