ON PENTAORGANYLSTIBORANE .3. REGIOSELECTIVE AND DIASTEREOSELECTIVE ADDITIONS OF ACETYLENIC AND ALLENIC ORGANOANTIMONY COMPOUNDS TO ALDEHYDES

The reaction of propargyl bromide (4a) with tributylstibine gave allenyltributylstibonium bromide (5), and its 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 MgBr2. All of the reactions had good chemoselectivity for aldehyde.