Introduction of a 3-Alkoxycarbonyl-2-propenyl Group at the ortho Position of Phenol and Naphthol via α-Aryloxy-γ-butyrolactone. Application to Syntheses of (±)-Nanaomycin A and a 1-Anthracenone

Abstract

Introduction of a (γ-alkoxycarbonyl) allyl group at the 2 position of 1-naphthol was achieved by a sequence of reactions involving a Claisen rearrangement, as illustrated in Chart 1, in overall yields of 62% (via 2a) and 50% (via 2b). By using the same technique, 5-methoxy- and 4, 5-isopropylidenedioxy-1-naphthols and 4-methoxyphenol were converted to the corresponding 4-aryl-2-butenoates (6a, b and 10), which underwent base-catalyzed cyclization to give dihydrofurans (7a, b and 11). Compounds 7a, b were readily transformed into (±)-nanaomycin A (14). 8, 10-Dimethoxy-1-anthracenone (19) was prepared from 6a in 77% yield by a standard method.