Differential reactivity of 3H-indole styrylcyanines: Intermolecular [4π + 2π] cycloaddition vs. proton - shift coupled six - electron electrocyclization

Abstract Differential reactivity of 3 H -indole styrylcyanines leading to oxazabicyclo[3,3,1]nonanes or N -alkenyl spiropyrans is reported. Quantum mechanical calculations show that the isomerization of styrylcyanine to N H -spiropyran dictates the differential reactivity and the initial step for both reactions is a six-membered ring formation via six - electron pericyclic reactions.