Photolysis of olefinic N-chloropyrrolidinones, N-chlorosuccinimides and N-chloro-oxazolidinones: Reactivity of cyclic carboxamidyl, imidyl and carbamyl radicals in intramolecular reactions

Abstract

N-Chloro-alkenylpyrrolidinones, an N-chloro-alkenylsuccinimide and N-chloro-alkenyloxazolidinones were prepared as precursors of olefinic cyclic carboxamidyl, imidyl and carbamyl radicals constrained to undergo intramolecular reactions uniquely via their planar or slightly twisted (30–35°) Π N state (1,5-transfer of an allylic hydrogen, 5- exo or 6- exo cyclization to give bicyclo[2.2.1]azaheptane and bicyclo[3.2.1]azaoctane skeletons respectively), those intramolecular reactions being unaccessible to the planar Σ N state. Their photolysis gave products arising uniquely from intermolecular reactions of those nitrogen radicals (addition to an external olefin, hydrogen abstraction from the solvent, allylic hydrogen abstraction). An intramolecular reaction leading to bicyclo[3.3.0]azaoctane derivatives via 5- exo cyclization was observed with an N-chloro-alkenylpyrrolidinone and an N-chloro-alkenyloxazolidinone. In these two cases, both the Π N and the Σ N states of the cyclic amidyl radical allow orbital overlap for 5-exo cyclization.