An efficient method for targeting a variety of symmetrical and asymmetrical α-substituted dithiomalonates (DTMs) is described, utilizing 1H-imidazole-1-carbothioates as reactive acylating agents and MgBr2⋅OEt2/DBU or LiHMDS for soft or hard enolization conditions of thioesters, respectively. The utility of this methodology was demonstrated through the synthesis of the pyridopyrimidine mesoionic insecticides: