ORTHO PHOTOCYCLOADDITION OF SUBSTITUTED 4-PHENOXYBUT-1-ENES - IDENTIFICATION OF REARRANGED PHOTOCYCLOADDUCTS BY NMR

The ortho photocycloadducts, formed on irradiation of 3-tert-butyl-4-p henoxybut-1-ene (1a) and 3-acetoxy-4-(4-methoxyphenoxy)but-1-ene (1b) at 254 nm, underwent in situ rearrangement to tricyclic structures 4a, 5a, and 5b, 5b', respectively. Hydration of the vinyl ether function in 5a led to 6a, while a similar secondary reaction of 5b afforded 8b. A detailed NMR investigation of the rearranged ortho photocycloadduct s of both 1a and 1b revealed not only the relevant structures, but als o furnished configurational and conformational details.