carbocyclic four-memberedrings. The illumination of a solution in benzene by light bulbs gave rise to the all-cis 1:1 cycloadduct (11a) in 76 % yield. On its part, this compound reacted with cis-CO under the action of better sources for UV light with the formation of three isomeric 1:2 cycloadducts. Two of them underwent a photochemical dechlorination leading to a cyclobutene derivative. Albeit rather
Photoinduced addition reactions of chloranil (CA) with allyl ethyl ether 1, methyl methacrylate 2, vinyl acetate 3, styrene 4, α-chloro-styrene 5, and α, p-dichlorostyrene 6 gave cyclobutane products 10 to 15 respectively. Similar reaction of CA with indene 7 and (E)-β-bromostyrene 8 gave oxetanes 16 and 17 respectively. Products of photoinduced addition of CA with cyclohexene 9 are solvent dependent: