Photoaddition of ethenes to 1,4-naphthoquinone: factors influencing the site of reaction

Abstract

1,4-Naphthoquinone undergoes photocycloaddition to a variety of electron donor and electron acceptor ethenes giving spirooxetanes and/or cyclobutane derivatives. The site of addition onto the quinone depends on the electron donor character of the ethene, with the spirooxetane being generally favoured with ethenes of low oxidation potential. 2,3-Dimethylbut-2-ene, the strongest electron donor ethene studied, also gave a novel acyclic addition product involving the ethene moiety of the quinone. The two types of 1,4-naphthoquinone cycloadducts have appreciable in vitro cytotoxicity.