ISOMERIZATION OF BENZOPYRAN-2-IMINES IN [H-2(6)]DIMETHYL SULFOXIDE

When 2-imino-2H-benzopyran-3-carboxamide 1 (X = H) is dissolved in [H- 2(6)]dimethyl sulfoxide, NMR spectra show that a mixture of 1 and the isomeric -cyano-3-(2-hydroxyphenyl)prop-2-ene-1-carboxamide 3 (X = H) is present. Other benzopyran-2-imines behave similarly; the degree of isomerisation varies considerably, depending on the nature and positio n of the substituents present.