Tri- and difluoromethoxylated N-based heterocycles − Synthesis and insecticidal activity of novel F3CO- and F2HCO-analogues of Imidacloprid and Thiacloprid

The preparation of F3CO- and F2HCO-analogues of Imidacloprid and Thiacloprid and the evaluation of their biological activity have been performed. For this purpose, a first synthetic approach allowed the preparation of a desired F3CO-containing key intermediate. To allow a facile access to the second F2HCO-containing key intermediate, the difluoromethylation of hydroxylated N-based heterocycles has been developed using difluoromethyl triflate (a liquid non-ODS reagent) under air in aqueous conditions and with very short reaction time. The broad diversity of compatible heterocycles includes a large series of substituted hydroxy-pyridines, but also −pyrazoles, −pyrazine, −pyridazine, and −quinolines. The couplings of both key intermediates with the required 4,5-dihydro-N-nitro-1H-imidazol-2-amine and [N(Z)]-N-2-thiazolidinylidene-cyanamide were successfully achieved using literature conditions. This work enables the preparation of valuable building blocks, which could lead to the discovery of new bioactive entities.