ChemInform Abstract: The Synthesis of New Heterocycles Using 2‐(4‐Chloro‐1,3‐dihydro‐3,3,7‐trimethyl‐2H‐indol‐2‐ylidene) Propanedial.

Abstract

4-Chloro-2,3,3,7-tetramethyl-3H-indole (an indolenine) was produced by the reaction of 5-chloro-2-methylphenylhydrazine hydrochloride with 3-methylbutan-2-one via Fischer reaction. Exposure of the indolenine to the Vilsmeier reagent at 50°C produced a β-diformyl compound, 2-(4-chloro-1,3-dihydro-3,3,7-trimethyl-2H-indol-2-ylidene)propanedial. This dialdehyde was reacted with arylhydrazines, acetamidinium chloride, urea, thiourea, guanidinium chloride, and cyanoacetamide to give various 5-membered and 6-membered heterocyclic products, each carrying a 4-chloro-3,3,7-trimethyl-3H-indol-2-yl unit as a substituent, in excellent yields.