Cyclohexene → 7-hydroxy-3-(4-methoxyphenyl)-2H-1-benzopyran

Participants

Reaction Steps

As shown in Scheme 2, 7-benzyloxy-3-(4-methoxyphenyl)-2H-1-benzopyran (compound 1) was reacted with n-Bu4NI/BCl3 and BCl3 to give haginin E (compound 2a) at a yield of 79% and 7-hydroxy-3-(4-methoxyphenyl)-2H-1-benzopyran (4′-O-methyl haginin E, compound 2b) at a yield of 81%, respectively. Treatment of compound 1 with Pd(OH)2/C (Pearlman's reagent) and cyclohexene in refluxing ethanol promoted O-debenzylation and reduction of the chromene ring in one step, giving 7-hydroxy-3-(4-methoxyphenyl)-1-benzopyran (compound 3a) at a yield of 94%. Compound 3a was subsequently demethylated by use of n-Bu4NI/BCl3 to give equol (compound 3b) at a yield of 95%.

Provenance & Evidence