Photocyclization Reactions. Part 4 [1]. Synthesis of Naphtho[1,8-bc]-furans and Cyclohepta[cd]benzofurans Using Photocyclization of Ethyl 2-(8-Oxo-5,6,7,8-tetrahydro-1-naphthyloxy)acetates and Ethyl 2-(5-Oxo-6,7,8,9-tetrahydro-5H-benzocyclohepten-4-yloxy)acetates

Article abstract of DOI:10.1002/jhet.5570330124

Photocyclization reactions were carried out on ethyl 2-(8-oxo-5,6,7,8-tetrahydro-1-naphthyloxy)acetates 1a-e and ethyl 2-(5-oxo-6,7,8,9-tetrahydro-5H-benzocyclohepten-4-yloxy)acetates 2a-e in acetonitrile. Irradiation of 1a-e gave naphtho[1,8-bc]furanols 3a-e and naphtho[1,8-bc]furans 4a-e in 33-83% yields and ethyl acrylates 5b-d were produced in 3-25% yields during irradiation of 1b-d. On the other hand, 2a-e afforded cyclohepta[cd]benzofuranols 6a-e and cyclohepta[cd]benzofurans 7a-e in 44-87% yields. Ethyl acrylates 8b-d were also produced in 7-43% yields from irradiation of 2b-d. Substituent effects on photocyclization and reaction pathways are discussed.