Process for the preparation of the 3-(3-chloro-1h-pyrazol-1-yl)pyridine

Abstract

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.

1 - 7 . (canceled) 
     
     
         8 . A process for preparing 3-chloro-1-(pyridin-3-yl)-1H-pyrazole-5-carboxylic acid hydrochloride (10d) 
       
         
           
           
               
               
           
         
         comprising
 treating the alkyl 3-chloro-1-(pyridin-3-yl)-1H-pyrazole-5-carboxylate (10c) 
 
       
       
         
           
           
               
               
           
         
         with aqueous hydrochloric acid at a temperature of about 25° C. to about 100° C., wherein R is (C 1 -C 4 ) alkyl. 
       
     
     
         9 . The process of  claim 8 , wherein the temperature is about 90° C. 
     
     
         10 . A process for preparing 3-(3-chloro-1H-pyrazol-1-yl)pyridine (5b), 
       
         
           
           
               
               
           
         
         comprising
 mixing 3-chloro-1-(pyridin-3-yl)-1H-pyrazole-5-carboxylic acid hydrochloride with copper(II) oxide in an organic solvent at a temperature of about 80° C. to about 140° C. 
 
       
     
     
         11 . The process of  claim 10 , wherein the organic solvent is a polar aprotic solvent. 
     
     
         12 . The process of  claim 11 , wherein the polar aprotic solvent is N,N-dimethylformamide. 
     
     
         13 . The process of  claim 10 , wherein the amount of copper(II) oxide is stoichiometric.