Novel Syntheses of Nitrogen Heterocycles from Isocyanides

The direct copper(I)-catalyzed synthesis of oligosubstituted pyrroles from substituted methyl isocyanides and acceptor-substituted acetylenes as well as copper(I)-mediated route to pyrroles from substituted methyl isocyanides and non-activated terminal acetylenes have been investigated. 2-Substituted phenyl isocyanides were obtained by trapping of generated in situ ortho-lithiophenyl isocyanide with electrophiles. This strategy has been effectively employed for the new synthesis of substituted 3H-quinazolin-4-ones (-thiones) including the naturally occurring alkaloids deoxyvasicinone and tryptanthrine. The reactions of ortho-lithiophenyl isocyanide and other ortho-lithiohetaryl isocyanides with aldehydes, ketones, and carbon dioxide have been investigated in detail. Two novel rearrangements of the intermediate 2-lithio-4H-3,1-benzoxazines have been disclosed. A novel copper-catalyzed synthesis of benzimidazoles from ortho-bromoaryl isocyanides and primary amines has been developed.