AbstractReaction of 1′,3′,3′‐trimethylspiro[2H‐1‐benzopyran‐2,2′‐indolines] with 1,1‐bis[4‐(dimethylamino)phenyl]ethylene can give two types of isomeric products, 2,2‐bis[4‐(dimethylamino)‐phenyl]‐4‐{2‐methylidene‐1,3,3‐trimethylindoline}chromans (2a–e) and 1′,3′,3′‐trimethyl‐4‐{2,2‐bis[4‐(dimethylamino)phenyl]vinyl}‐spiro[chroman‐2,2′‐indolines](3a–d).These products and related compounds have been analysed by spectroscopic methods. The conformation of the dihydropyran ring and the chemical