On pentaorganylstiborane: III. Regio- and diastereoselective additions of acetylenic and allenic organoantimony compounds to aldehydes

Abstract

The reaction of propargyl bromide ( 4a) with tributylstibine gave allenyltributylstibonium bromide ( 5), and its corresponding pentaorganylstiborane reacted with aldehyde to give homopropargylic alcohol ( 10a) exclusively in good yield. However, the reaction of 1-bromo-2-butyne ( 4b) with tributylstibine gave acetylenic stibonium bromide ( 6b), and its corresponding stiborane reacted with aldehyde to give allenic alcohol ( 9b) as major product. The reaction of 3-bromo-1-trimethylsilyl-1-propyne ( 4d) with tributylstibine also gave acetylenic stibonium bromide ( 6d), but the major product of the reaction of its corresponding stiborane with aldehyde was acetylenic alcohol ( 10d), and the regioselectivity was very high in the presence of LiBr. Further, it was found that the allenic stibonium bromide ( 12) was obtained by the reaction of 3-bromo-1-butyne ( 11) with tributylstibine. The corresponding stiborane ( 13) reacted with aldehyde to give acetylenic alcohol ( 14) exclusively in good yield, and the diastereoselectivity was moderately in favour of the threo isomer in the presence of MgBr 2. All of the reactions had good chemoselectivity for aldehyde.