Furan derivatives. Part 6. On effect of ring size in synthesis of 4,5-dihydro-3H-naphtho[1,8-bc]furans and their analogues

Abstract

Furan derivatives have been synthesized from 7-hydroxy-4-methoxy-2,3-dihydroinden-1-one (7b), 8-hydroxy-5-methoxy-1,2,3,4-tetrahydronaphthalen-1-one (4b), 4-hydroxy-1-methoxy-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-one (8b), 6-hydroxy-2a,3-dihydro-2H-naphtho[1,8-bc]furan-5(4H)-one (9b), 7-hydroxy-2,3,3a,4-tetrahydronaphtho[1,8-bc]pyran-6(5H)-one (10b), and 7-hydroxy-2,2a,3,4-tetrahydrocyclohepta[cd]benzofuran-6(5H)-one (11b). Hydroxy ketones such as (4b), (8b), (10b), and (11b) which have a strong intramolecular hydrogen bond between the hydroxy and the carbonyl groups easily produced the furan derivatives (1), (13), (15), and (16). However, the hydroxy ketones (7b) and (9b) in which the intramolecular hydrogen bond was weak failed to give the furan derivatives (12) and (14).