Coumarins and related compounds. Part XXI. A reinvestigation of the reaction between 1-naphthol and 2-formyl-2-phenylacetonitrile

Abstract

Controversy arose between Baker and Ghosh over whether a compound of m.p. 169–170° obtained in the title reaction was 3-phenylnaphtho[1,2-b]pyran-2-one (2) or the corresponding naphthopyran-4-one (1). Synthesis of compounds (1) and (2) showed that both these authors were wrong. The reaction has now been repeated and found to give a mixture of 3-(4-hydroxy-1-naphthyl)-2-phenylacrylonitrile (5), 3-hydroxy-3-(4-hydroxy-1-naphthyl)-2-phenylpropiononitrile (9), and 3,4-dihydro-4-(4-hydroxy-1-naphthyl)-3-phenylnaphtho[1,2-b]-pyran-2-one (11). Thermal condensation between 1-naphthol and 2-formyl-2-phenylacetonitrile gave exclusively the naphthopyranone (2) in moderate yield.