Thermolysis of 1-phthalimidoaziridine-2-carbonitriles in the presence of dipolarophiles

Thermolysis of trans-3-phenyl-1-phthalimidoaziridine-2-carbonitrile and trans-1-phthalimidoaziridine-2,3-dicarbonitrile in the presence of several dipolarophiles involves 1,3-dipolar cycloaddition to intermediate azomethine ylides and leads to 1-phthalimidopyrrolidine derivatives with good yields and high stereoselectivity. Thermally induced opening of the three-membered ring in trans-2,3-disubstituted 1-phthalimidoaziridines occurs in conrotatory mode to produce the corresponding cis-azomethine ylides in keeping with the orbital symmetry conservation rules. The relative configuration of substituents in the dipolarophiles is retained, which implies concerted mechanism of the addition.