Photochemical Ring Enlargements of Two α-Cyanocycloalkanones

Abstract

The photochemical transformations undergone by 2-cyano-2-methylcycloheptanone (1) and 2-cyano-2-methylcyclohexanone (2) have been studied in methanol and aqueous dioxane. In the former solvent, 1 is isomerized to three products in the ratio 78:8:13, corresponding to the enals 3a and 3b, and a new ring expansion product 4, respectively. In aqueous dioxane, the cyclic imide 6 was obtained in 18% yield. Cycloalkanone 2 in methanol produces four products in the ratio 61:30:7:1, these being the isomeric enals 8a and 8b, the ester 9, and the ring expansion product 10. No imide related to 6 could be obtained from irradiation of 2 in aqueous dioxane.