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

Abstract

Reactions of the boranes, BH(C₆F₅)₂ or 9-BBN, with azodicarboxylates or an azodicarbonylamide provide facile access to NBO heterocyclic compounds. The products [(C₆F₅)₂BOC(X)N]₂ X = OEt 1, OiPr 2, OCH₂CCl₃3, OCH₂Ph 4, NC₅H₁₀5) and [(9-BBN)OC(X)N]₂ (X = OEt 6, OiPr 7, NC₅H₁₀8) and [Ph₂B)OC(OtBu)N]₂9 were prepared. In another variation, (nacnac)AlH₂ (nacnac = (C₆H₃iPr₂NC(Me))₂CH) afforded the Al-heterobicycle [(nacnac)Al(H)OC(OEt)N]₂10. The mechanism for the formation of these products is proposed to involve transient hydroboration or hydroalumination of the NN double bond.