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Paper | Regular issue | Vol 55, No. 3, 2001, pp.511-521
Published online, 1st January, 1970
DOI: 10.3987/COM-00-9127
A Study of the Photochemical Isomerization in β-Lactam Rings

Roberto Alcázar, Pedro Ramírez, Rubén Vincente, María J. Mancheño, Miguel A. Sierra, and Mar Gómez-Gallego*

*Departamento de Química Orgánica I., Facultad de Química., Universidad Complutense de Madridas, Ciudad Universitaria, E-28040 Madrid, Spain


The cis to trans or trans to cis photoisomerization of 2-azetidinones (1) is reported. The outcome of the photochemical process is controlled by the substitution on the nitrogen atom and by the ability of the substituents at C3 and C4 positions to stabilise radicals. N-Aryl-2-azetidinones are unreactive even after several hours of UV-light irradiation. N-Alkyl-2-azetidinones cleanly isomerize under the same conditions, providing a smooth procedure for the ring isomerization of β-lactams.