Sequential[3,3]Sigmatropic Rearrangement of 1 -Aryloxy-4-(4′-coumarinyloxy)but-2-ynes

Abstract

1-Aryloxy-4-(4′ -coumarinyloxy) but-2-ynes (4) when subjected to thermal rearrangement in refluxing N,N-diethyl aniline gave 4-methyl-3-(2′ -hydroxyphenyl) pyrano[3,2- c] [1]-benzopyran-5(4H)-one derivatives (5). The same products (5) were also obtained when 4-aryloxymethyl pyrano[3,2- c][1]benzopyran-5(2H)-ones (6) were refluxed in N,N-diethyl aniline for 5 hr. These phenolic products (5) were characterised by the preparation of their acetate derivatives with acetic anhydride and pyridine. Addition of toluene-4-sulphonic acid during the thermal rearrangement of 4 or 6 showed no effect in the formation of the product.