Photochemical reactions. 143^rd communication. Photochemistry of 5,6‐epoxy‐1,3‐dienes in the ionone series. Influence of a hydroxy group in the 7‐position

Abstract

The synthesis and photolyses of the epoxydiene (E)-5 are described. On triplet excitation (1 > 280 nm, acetone), (E)-5 undergoes initial cleavage of the C(5)-0 bond leading to the intermediate c.Presumably an H-shift (c-+e) followed by the fragmentation of the 1,Cdiradical e leads (via the enol37) to the diketones (E)-6 and (Z)-12. Alternatively, cleavage of the C(6)-C (7)