A novel one‐step synthesis of 4<i>H</i>‐furo[3,4‐<i>b</i>]pyrans and a transformation into a difuro[3,4‐<i>b</i>: 3′,4′‐<i>e</i>]pyridine

Abstract

Abstract A simple one‐step synthesis of 2‐amino‐4‐aryl‐5‐oxo‐4 H ‐furo[3,4‐ b ]pyran‐3‐carbonitriles 7 is described. It involves reaction of 2,4(3 H ,5 H )‐furandione (β‐tetronic acid) ( 5 ) with arylmethylenemalononitriles 4 in basic medium. Some substituent effects are noted and the assignments of 13 C‐NMR spectra are discussed. Ring transformation of the furo[3,4‐ b ]pyran 7a leads to the difuro[3,4‐ b :3′,4′‐ e ]pyridine 9 .