Nitriles in heterocyclic synthesis. A novel synthesis of spiropyran‐4‐ylindolidene derivatives

Abstract

Abstract The structure of the products of reaction of 2‐oxo‐3‐dicyanomethylidene‐2,3‐dihydroindole ( 1a ) and 2‐oxo‐3‐cyanoethoxycarbonylmethylidene‐2,3‐dihydroindole ( 1b ) with the pyrazolin‐5‐one derivatives 2a,b could be established via 13 C nmr and high resolution 1 H nmr to be the spiropyranylindolone derivatives 5a‐d .