11 Organic photochemistry

Abstract

This review covers the literature during publication year 2002 concerning organic photochemistry. The general areas of photochemical applications in organic synthesis and mechanistic studies are both covered. This review is selective rather than comprehensive, due to the large volume of publications in this field. Biological photochemistry is not covered.

Of particular note in 2002 is the development of a smart photochromic system which links bis-naphthopyrans through a bis-thiophene moiety. The thiophene tether undergoes a time-dependent change during irradiation, with its electron-donating ability varying due to hybridization changes at the spirocyclic carbon. The development of orthogonal photocleavable protecting groups, with intramolecular or intermolecular discrimination, was described. Chiral discrimination in excited-state proton transfer was demonstrated through an enhanced proton transfer rate from 5,8-dicyano-2-naphthol to enantiopure 2-butanol, compared to the racemic solvent. Progress in photoinduced asymmetric induction for photocyclization and geometric isomerizations was reported. The highest levels of asymmetric induction were achieved in zeolites in combination with ionic or neutral chiral auxiliaries.