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

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 Ca-3(PO4)(2) provides redox activity on the Pd through electron donation.

Automated summary

In this study, originally developed heterogeneous Pd catalysts were used for selective hydrodechlorination reactions under continuous-flow conditions to synthesize an SDHI fungicide intermediate. Under optimal reaction conditions with tetrabutylammonium acetate, the hydrodechlorination reaction from a chlorodifluoromethyl-substituted pyrazole derivative proceeded selectively to afford the product quantitatively at a reaction rate of 1.5 h(-1) of the SVmol value. The roles of the binary support were investigated through characterization techniques, and it was revealed that the carbon support generated catalytic activity for the supported Pd species, while Ca-3(PO4)(2) provided redox activity on the Pd through electron donation.