Contributions of the Chemistry of Boron, 236. In Quest of New and Stable Bis(organyloxy)boranes (RO) 2 BH for Catalytic Hydroboration

Abstract New and stable bis(organyloxy)boranes, 1,3,2‐dioxaborolanes and 1,3,2‐dixoaborinanes have been prepared (i) from the corresponding diol and BH 3 ·THF and (ii) from 1,2‐diketones and BH 3 ·THF. They were characterized by spectroscopic techniques. The BH stretching frequency seems to be a measure of ring strain and Lewis acidity. The compounds have been qualitatively tested in the transition‐metal‐catalysed hydroboration of cyclopentene, and the dioxaborinane 11 proved to be superior to the 1,3,2‐dioxaborolanes 9 and 18 .