Benzopyrans. Part 38.1 Reactions of 4-Oxo-4H-1-benzopyran-3-carbaldehyde, -3-carbonitrile and -3-carboxylate with Chloroacetone and a Note on the Stereochemistry of Benzo[b]cyclopropa[e]pyrans

Abstract

The title benzopyranones 1–3 give the benzo[b]furan 7 and the benzo[b]cyclopropa[e]pyrans 8 and 9 with chloroacetone in acetone containing anhydrous potassium carbonate and a catalytic amount of potassium iodide but give the 1-benzopyranones 10, 11 and 14 in dichloromethane in the presence of Brockman neutral alumina, respectively.