1,3-vs. 1,5-Cyclization of azomethine ylides derived from 1-azabuta-1,3-dienes and difluoro- and dichlorocarbenes. Experimental and quantum-chemical study

1,3- vs. 1,5-Cyclization of azomethine ylides derived from 1-azabuta-1,3-dienes and difluoro- and dichlorocarbenes, leading to halogenosubstituted aziridine or pyrrole derivatives, was investigated. Calculations of the reaction profiles were carried out at the B3LYP/6-31G level to evaluate factors responsible for the predominant transformation pathways of the ylides.