New synthesis of 2,2 '-heteroarylpyrroles from heteroarylchlorocarbenes

2,2'-Pyridyl- and 2,2'-thienylpyrroles containing substituents at the 1- an d 3-positions of the pyrrole ring have been prepared from the reaction of h eteroarylchlorocarbenes with 1-azabuta-1,3-dienes. Laser flash photolysis o f heteroarylchlorocarbene in isooctane in the presence of 1-azabuta-1,3-die ne yields an azomethine ylide (lambda=550 nm) as an intermediate. The kinet ic parameters for the ylide formation and further 1,5-intramolecular cycliz ation to the pyrrole ring have been determined. (C) 1999 Elsevier Science L td. All rights reserved.