BENZAZOLE-N-BH3 ADDUCTS - REDUCTIVE TRANSPOSITION OF 2-BENZIMIDAZOLE,2-BENZOTHIAZOLE AND 2-BENZOXAZOLE N-BH3 ADDUCTS TO 1,3,2-BENZIMIDAZABOROLE, 1,3,2-BENZOXABOROLE, AND 1,3,2-BENZOTHIAZABOROLE

1,3,2-Benzimidazaborole, 1,3,2-benzoxaborole, and 1,3,2-benzothiazabor ole were synthesized from the corresponding 2-benzazole N-BH3 and 2-be nzazole S-BH3 adducts through a reductive transposition from the isolo bal fragment X-C(sp(2)) = N(sp(2)) - B(sp(3)) (X = N, O, S) to the fra gment X-B(sp(2)) = N(sp(2)) - C(sp(3)). N-BH, substitution shifts to l ower frequencies 4-H, C-3a, and C-7a resonances. The X-ray diffraction analysis of 2-(o-methoxyphenyl)benzothiazole N-BH3 adduct is reported . Two new tetracyclic boron-bridged compounds were observed as by-prod ucts -oxa-1-bora[3,4,7,8]-dibenzobycyclo[4.3.0]-nona-3, 7-diene, 6d, a nd bora-[3,4,7,8]dibenzobycyclo[3.4.0]nona-3,7-diene, 15d, when 2-(o-m ethoxyphenyl)-1-ethylbenzimidazole-BH3 6b and 2-(o-methoxyphenyl)-benz othiazole-BH3 15b adducts were heated. (C) 1996 John Wiley & Sons, Inc .