摘要:
Photocyclization of aryl vinyl ethers reportedly proceeds via carbonyl ylide intermediates. The photochemical behavior of several aryl vinyl ethers, which incorporate a pendant alkene side chain, was explored. Naphthyl vinyl ethers 1c and 1d provided products that are consistent with photocyclization and subsequent intramolecular ylide-alkene addition. Product distribution is influenced by solvent and temperature effects. Thus, irradiation of 1c in toluene provides 9a in 87% yield. However, irradiation of 1c in methanol/toluene (1:1) provides 3c (45%), 11 (24%), and 12 (23%). Product 12 results from photoinitiated intramolecular [2 + 2] cycloaddition of the butenoate ester side chain to the naphthalene system.