Furan derivatives. part 11 [1]. on substituent effects in the synthesis of 3,4,5,6‐tetrahydrocyclohepta[cd]benzofurans

Abstract

AbstractTetrahydrocyclohepta[cd]benzofurans 7a‐e were synthesized by the treatment of (5‐oxo‐tetrahydro‐5H‐benzocyclohepten‐4‐yloxy)acetic acids 5a‐e with sodium acetate in acetic anhydride or by heating of their esters 6a‐e with sodium hydroxide or sodium hydride in dioxane. The yield of furans 7 decreased as a substituent R of acids 5 or esters 6 was changed from hydrogen to a methyl, ethyl, or isopropyl group. When R was a phenyl group furan 7e was always prepared in good yield. Sodium hydride was a useful base for synthesis of tetrahydrocyclohepta[cd]benzofurans.