ORGANIC SYNTHESIS USING HALOBORATION REACTION. PART 9. A DIRECT AND SELECTIVE SYNTHESIS OF (Z,Z)-1-BROMO-1,3-DIENES AND (E,Z)-1,3-DIENES BY THE HYDROBORATION-BROMOBORATION SEQUENCE OF TWO ALKYNES

Article abstract of DOI:10.1016/S0040-4039(00)84153-2

1-Alkenyldibromoboranes readily obtainable by the hydroboration of first alkynes with dibromoborane-dimethyl sulfide followed by treatment with tribromoborane, react without any difficulty with second 1-alkynes as bromoborating agents to give (1-alkenyl)(2-bromo-1-alkeny)-bromoboranes (5).The reaction of 5 with iodine in the presence of potassium acetate provides (Z,Z)-1-bromo-1,3-dienes (6), specifically, which are readily converted into the corresponding (E,Z)-1,3-dienes (7) by treatment with t-butyllithium and methanol.