Abstract
In the reaction of tribromoborane with 1-alkynes, cis-addition occurred to give [Z] -2-bromo-1-alkenylboranes. On the other hand, bromoboration reaction of acetylene gave trans-addition product. Both reactions proceeded stereoselectively and (bromoalkenyl) boranes could be obtained with high selectivity. trans-Alkenes, α, β-unsaturated ketones, α, β-unsaturated esters were prepared stereoselectively by the stepwise crosscoupling reaction of the haloboration adducts. As the application, prostaglandin B1 methyl ester was synthesized. This method was also used for the synthesis of the polyenes which were converted to the polycyclic compounds by the intramolecular Diels-Alder reaction. Bromoboration reaction of allene provided (2-bromoallyl) borane and the reaction of (2-bromoallyl) borane with carbonyl compounds was also described.
