Optimization of the route to sap-feeding insecticide Tyclopyrazoflor featuring [3 + 2] cyclization of 3-hydrazinopyridine dihydrochloride and methyl acrylate is described. The key impurities in the [3 + 2] cyclization were identified and successfully controlled after optimization. The hazardous oxidation with an incompatible combination of potassium persulfate (K2S2O8) and N,N-dimethylformamide (DMF) for the synthesis was replaced with potassium ferricyanide (K3Fe(CN)6) in water. The two elimination impurities in the ethylation to Tyclopyrazoflor were successfully controlled under optimal conditions. The overall yield for this 7-step synthesis of Tyclopyrazoflor was improved from 10% to 41%.

Fit-for-purpose optimization of the route to tyclopyrazoflor featuring [3 + 2] cyclization of 3-hydrazinopyridine dihydrochloride and methyl acrylate

2019 Fall National Meeting

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