Photocycloaddition of cyclohex-2-enones to alkylidenemalononitriles (1,1-dicyanoalkenes)

Abstract

5,5-Dimethylcyclohex-2-enone (1a) photocycloadds to ethylidenemalononitrile (2a) to give 5-oxobicyclo[4.2.0]octane-7,7-dicarbonitriles with slight preference, in analogy to results already described for light induced reactions between cyclohexenones and acrylonitrile (AN). In contrast, irradiation of 1a in the presence of isopropylidenemalononitrile (2b) leads to selective formation of the (opposed) 2-oxo regioisomers. Similar trends in product distribution regarding the orientation of addition are also observed in light-induced reactions of 2-alkynylcyclohexenone 1b with either 2a or 2b.