alkynylstannanes. The Diels-Alder reactions of 1-4 with isoprene in hexanes proceed rapidly at 25 degrees C, affording 1,4-cyclohexadiene products in high yield with high regioselectivity. Reactions carried out in CH(2)Cl(2) exhibited an alternative product that results from the formal 1,4-alkynylboration of the diene. The alkynylboration intermediates can undergo further conversion to the Diels-Alder adducts under
从BCl(3)或BBr(3)与相应的炔基
锡烷的
硼锡交换反应中很容易就地生成炔基二卤
硼烷1-6。1-4与
异戊二烯在己烷中的Diels-Alder反应在25℃下快速进行,以高收率和高区域选择性提供1,4-环
己二烯产物。在CH(2)Cl(2)中进行的反应显示出另一种产物,该产物是由二烯的正式1,4-炔基
硼化作用产生的。在反应条件下,炔基
硼化中间体可以进一步转化为Diels-Alder加合物。讨论了这些反应的机理。