N-Arylmethylene and N-benzhydrylideneamines react with fluorocarbene yielding fluoro-substituted azomethine ylides that undergo 1,3-pi-cyclization into aziridines. Generation of fluoroylides in the presence of dipolarophiles (dimethyl maleate or dirnethyl acetylenedicarboxylate) led to the reaction of 1,3-dipolar cycloaddition resulting in substituted 2-pyrrolines or pyrroles. 2-Fluoroaziridines, products of N-alkyl-N-benzhydrylideneamines 1,3-pi-cyclization, in the presence of acid catalysts suffer isomerization into alpha-fluoroimines and 1,3-disubstituted indoles.