One-pot Four-component Reaction between Arylamines, Arylglyoxals, Cyclohexyl Isocyanide, and Acetylene Diesters: An Efficient Synthesis of 2H-iminopyran Derivatives

A facile synthesis of highly functionalized 2H-iminopyran derivatives by the multi-component reaction of cyclohexyl isocyanide, dialkyl acetylenedicarboxylates, arylglyoxals and arylamines is described. The zwitterionic intermediate produced by addition of cyclohexyl isocyanide to electron-deficient acetylene diesters was trapped by the electrophilic imine moiety of α-iminoketones, derived from arylglyoxals and arylamines, to afford an inner salt intermediate which converted to 2H-iminopyran derivatives by an intramolecular cyclization.