TRIFLIC ACID-PROMOTED REGIO AND STEREOSELECTIVE SYNTHESIS OF POLYFUNCTIONALIZED ENAMINONES FROM DIBENZYLIDENE KETONES AND ORGANIC AZIDES

A stereoselective synthesis of α-aryl Z enaminones was developed by TfOH-promoted condensation of dibenzylidene ketones with organic azides. The cascade reactions involve the sequence of 1,3-dipolar cycloaddition of alkyl azides with the enone, aziridine formation, and 1,2-aryl migration via phenonium ion, whose stereochemical control by a strong N–H…O=C intramolecular hydrogen bond affords Z isomer exclusively. The readily available starting materials and ease of handling of TfOH are experimental advantages that give diversely substituted enaminones with total control of functionalization along the N–C=C–C=O conjugated system.