PREPARATION AND SOME REACTIONS OF (ACYLAMINO)DIORGANOBORANES

The carboxamides RCONH2 [R = Ph (1), tBu (2)] react with BEt3 and with (9H-9-BBN)2 to give the (acylamino)diethylboranes 3, 4 and the 9-acylamino-9-BBN 5, 6, respectively. Compounds 3 and 4 are largely monomeric (NMR) in solution and dimeric as crystalline solids [X-ray structure of (4)2]. The 9-BBN derivatives 5 and 6 are associated and probably polymeric in solution (NMR). The 1:1 adducts 7 and 8 containing the NCOBHB ring (X-ray structure of 7) are formed on the reaction of 3 and 4 with (9H-9-BBN)2 by borane exchange. The former is also obtained directly by treating compound 1 or 2 with (9H-9-BBN)2. Compound 7 reacts at 140 - 150-degrees-C to give the air-stable OBNCNC heterocycle 11 (X-ray structure).