Access to 2,3-dihydro-4 <i>H</i> -furo[3,2- <i>c</i> ]chromen-4-ones based on the mechanistic study of the formation of a tiny amount of byproduct isolated from Mn(III)-based oxidation of 1-(2-methoxynaphthalen-1-yl)butane-1,3-dione with 1,1-diphenyl

Abstract Acidolysis of 3-acetyl-2-(2-methoxyaryl)-4,5-dihydrofurans prepared by the Mn(III)-based oxidation of 1-(2-methoxyaryl)butane-1,3-dione enols with 1,1-diarylethenes efficiently gave 3-(2,2-diarylvinyl)-2-methyl-4H-chromen-4-ones, which were oxidized with Mn(OAc)3•2H2O to give 2,2-diaryl-4-oxo-2,3-dihydro-4H-furo[3,2-c]chromen-3-yl acetates. The required (methoxyaryl)butanediones were synthesized by direct BF3-assisted acetoacetylation of 2-methoxynaphthalene, 1-methoxynaphthalene, 1,5-dimethoxynaphthalene, 2,6-dimethoxynaphthalene, 2,7-dimethoxynaphthalene, 9-methoxyphenanthrene, and anisole using Ac2O. The mechanism for the formation of 2-(2,2-diphenylvinyl)-3-methyl-1H-benzo[f]chromen-1-one could be explained by the acid-catalyzed ring-opening/recyclization of the (2-methoxynaphthyl)dihydrofurans. The plausible reaction pathway to the final 4-oxo-2,3-dihydro-4H-benzo[f]furo[3,2-c]chromen-3-yl acetates was demonstrated by the Mn(III)-based oxidation of the alternatively synthesized intermediates.