Photochemistry of N-alk-4-enyl- and N-alk-5-enyl-phthalimides: two different types of cyclization reaction

Abstract

Photochemical reactions of N-alk-4- and -5-enylphthalimides (1a–e) have been investigated. In the photolyses of acetonitrile solutions of (1a–e), intramolecular cyclization reactions accompanying C(O)–N bond cleavage to give (2a–e) were generally predominant, together with intramolecular hydrogen abstraction in some cases. Photolyses of cis- and trans-N-hex-4-enylphthalimides [cis-(1e) and trans-(1e)] in acetonitrile solutions showed stereospecific cyclization reactions; irradiation of cis-(1e) gave cis-(2e) and that of trans-(1e) gave trans-(2e) selectively with low conversion. In methanol (1d), which has a vinyl ether moiety, gave different types of cyclization product: namely, (8a) and (9a), methanol-incorporated products probably resulting from an intramolecular electron transfer process.