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:
Disclosed are compounds of Formula 1, wherein X is O or S; Y is O or S; and R1, R2, R3 and R4 are as defined in the disclosure. Also disclosed are compositions containing the compounds of Formula 1 and methods for controlling an invertebrate pest comprising contacting the invertebrate pest or its environment with a biologically effective amount of a compound or a composition of the invention.