Reactions of donor-acceptor cyclopropanes or benzylidenemalonate with benzyl azide by generating gallium trichloride 1,2-zwitterionic complexes

Resumo

The reactions of 1,2-zwitterionic complexes, generated from 2-arylcyclopropane-1,1-dicarboxylates (ACDC) or benzylidenemalonate and gallium trichloride, with benzyl azide proceeds as a formal [3+2] cycloaddition to form dihydro-1,2,3-triazoles. The latter, when the reaction mixture is treated with 10% aqueous HCl, undergo retrocyclization with elimination of diazomalonate. The reaction of ACDC, benzyl azide, and GaCl₃ with simultaneous mixing of the reagents leads to the interception of the 1,3-zwitterion, with this stage being accompanied by both the cyclization to substituted 1,2,3-triazinine and the elimination of a nitrogen molecule to form 3,4-dihydro-2H-1,2-oxazine structure, which after acid hydrolysis gives substituted 3-hydroxypyrrolidin-2-one.