Studies of [3,3]sigmatropic rearrangements: rearrangement of 3-(4-p-tolyloxybut-2-ynyloxy)[1]benzopyran-2-one

Abstract

3-(4-p-Tolyloxybut-2-ynyloxy)[1]benzopyran-2-one (1), when refluxed in chlorobenzene, ethyl benzene, or xylene, gave exclusively 1-(p-tolyloxymethyl)pyrano[2,3-c][1]benzopyran-5(3H)-one (2), whereas through an ionic or radical pathway 2-methyl-1-(p-tolyloxymethyl)furo[2,3-c][1]benzopyran-4-one (3) was the exclusive product.