Chemistry of 1,5-diketones: IV. New aspects of the chemistry of 1,5-Dioxo compounds of the 2H-pyran-2-one series

Abstract

Reactions of 3,3′-(phenylmethanediyl)bis(4-hydroxy-6-methyl-2H-pyran-2-one) with electrophilic (PCl5, CF3COOH, BF3 · Et2O) and nucleophilic reagents (P2S5) in different solvents were studied. The reactions with boron trifluoride-diethyl ether complex in acetic acid and with trifluoroacetic acid gave 4a-hydroxy-3,7-dimethyl-10-phenyl-10,10a-dihydro-1H,4aH,9H-dipyrano[4,3-b: 3′,4′-e]pyran-1,9-dione, while 3,7-dimethyl-10-phenyl-1,9-dioxo-1H,9H-dipyrano[4,3-b: 3′,4′-e]pyran-5-ium tetrafluoroborate was obtained in the reaction with BF3 · Et2O in diethyl ether. Conditions were found for the synthesis of 4-hydroxy-6-methyl-3-[(6-methyl-2-oxo-4-sulfanyl-2H-pyran-3-yl)(phenyl)methyl]-2H-pyran-2-one by reaction of 3,3′-(phenylmethanediyl)bis-(4-hydroxy-6-methyl-2H-pyran-2-one) with diphosphorus pentasulfide.