摘要:
The kinetic hydroboration of allenylsilane 5 with ((d)Ipc)(2)BH at -40 degrees C provides allylborane 9Z with >= 12:1 selectivity. When the hydroboration is performed at temperatures above -40 degrees C, 9Z isomerizes to the thermodynamically more stable allylborane 9E with >20:1 selectivity. Subsequent treatment of 9Z or 9E with aldehydes at -78 degrees C provides syn- or anti-beta-hydroxyallylsilanes, 7 or 8, respectively.