Transient hydroboration and hydroalumination of activated azo-species: avenues to NBO and NAlO-heterobicycles.

Reactions of the boranes, BH(C 6 F 5 ) 2 or 9-BBN, with azodicarboxylates or an azodicarbonylamide provide facile access to NBO heterocyclic compounds. The products [(C 6 F 5 ) 2 BOC(X)N] 2 X = OEt 1, OiPr 2, OCH 2 CCl 3 3, OCH 2 Ph 4, NC 5 H 10 5) and [(9-BBN)OC(X)N] 2 (X = OEt 6, OiPr 7, NC 5 H 10 8) and [Ph 2 B)OC(O t Bu)N] 2 9 were prepared. In another variation, (nacnac)AlH 2 (nacnac = (C 6 H 3 iPr 2 NC(Me)) 2 CH) afforded the Al-heterobicycle [(nacnac)Al(H)OC(OEt)N] 2 10. The mechanism for the formation of these products is proposed to involve transient hydroboration or hydroalumination of the NN double bond.