Metal-free, I2-promoted direct synthesis of 2-cyano-substituted maleimides via a unique 3,3-dicyano-2-arylacrylic acid intermediate

Abstract

A robust, I₂-mediated cyclization reaction was developed for the synthesis of 2-cyano-substituted maleimides from arylethylidene malononitriles and amines via unique a 3,3-dicyano-2-arylacrylic acid intermediate. The reaction duration was short and devoid of an expensive transition-metal catalyst, ligands or toxic carbon monoxide. We executed an I₂/DMSO-mediated desirable oxidation of the C(sp³)–H bond of the carbonyl precursor followed by the formation of a 3,3-dicyano-2-arylacrylic acid intermediate. Use of readily available starting materials under mild and operationally simple reaction conditions are the major advantages of this strategy.