3-(3-chloro-1H-pyrazol-1-yl)pyridine is prepared by cyclizing 3-hydrazinopyridine-dihydrochloride with a dialkyl maleate to provide an alkyl 5-oxo-2-(pyridin-3-yl)pyrazolidine-3-carboxylate, by chlorinating to provide an alkyl 3-chloro-1-(pyridin-3-yl)-4,5-dihydro-1H-pyrazole-5-carboxylate, by oxidizing to provide an alkyl 3-chloro-1-(pyridin-3-yl)-1H-pyrazole-5-carboxylate, by converting the ester to the carboxylic acid by hydrolysis to provide 3-chloro-1-(pyridin-3-yl)-1H-pyrazole-5-carboxylic acid hydrochloride, and by removing the carboxylic acid by a decarboxylation reaction.
