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