PYRAZOLE COMPLEXES OF ACYLOXYDIALKYLBORANES

The reaction of Me3CCOOBEt2 with pyrazole led to the formation of the stable addition complex 1, which was found to be monomeric in solution . The reaction of 9-H-9-borabicyclo[3.3.1]nonane (9-H-9-BBN)(2) with p yrazole and pivalic acid yielded a similar complex Me2CCOO(9-BBN)-pzH 2. Crystallographic analysis of 2 revealed a dimeric structure due to the strong hydrogen bonding between azole hydrogen and carbonyl oxygen . The one boron-carbon bond of compound 1 cleaves readily with triethy lborane at 20 degrees C with the evolution of ethane, giving a species Me2CCOO(BEt2)(2)pz 3 with a seven-membered heterocyclic ring as the m ain structural feature. (C) 1998 Elsevier Science S.A. All rights rese rved.