Catalytic hydrogenative dechlorination reaction for efficient synthesis of a key intermediate of SDHI fungicides under continuous-flow conditions

Abstract

Selective hydrodechlorination reactions under continuous-flow conditions for the synthesis of an SDHI fungicide intermediate were investigated using originally developed heterogeneous Pd catalysts. Under optimal reaction conditions accompanying the use of tetrabutylammonium acetate, the desired hydrodechlorination reaction from a chlorodifluoromethyl-substituted pyrazole derivative proceeded selectively to afford the product quantitatively at 1.5 h⁻¹ of the SVmol value. We tried to access the roles of the present binary support by a series of characterization techniques and revealed that the carbon support generates catalytic activity to the supported Pd species and Ca₃(PO₄)₂ provides redox activity on the Pd through electron donation.