Insertion of nitriles into zirconocene 1-aza-1,3-diene complexes: chemoselective synthesis of N-H and N-substituted pyrroles.

The direct insertion of nitriles into zirconocene-1-aza-1,3-diene complexes provides an efficient, chemoselective, and controllable synthesis of N-H and N-substituted pyrroles upon acidic aqueous work-up. The outcome of the reaction (that is, the formation of N-H or N-substituted pyrroles) results from the different cyclization patterns, which depend on the relative stability and reactivity of the enamine-imine tautomers formed by hydrolysis of the diazazirconacycles.