The first chemoselective tandem acylation of the Blaise reaction intermediate: a novel method for the synthesis of alpha-acyl-beta-enamino esters, key intermediate for pyrazoles

The Blaise reaction intermediate, a zinc bromide complex of beta-enamino ester, could be activated in situ by addition of a stoichiometric or catalytic amount of n-BuLi to allow chemoselective tandem C2-acylation providing alpha-acyl-beta-enamino esters, which are valuable intermediates for the syntheses of tri- and tetrasubstituted pyrazoles.