Solvent‐free route to β‐enamino dichloromethyl ketones and application in the synthesis of novel 5‐dichloromethyl‐1<i>H</i>‐pyrazoles

Abstract

Abstract magnified image An efficient procedure to prepare a series of five 4‐amino‐1,1‐dichloro‐3‐penten‐2‐ones [CHCl 2 C(O)CHC(Me)NR 1 R 2 , where R 1 /R 2 = H/Ph, H/Bn, H/CH 2 CH 2 OH, (CH 2 ) 4 ,(CH 2 ) 2 O(CH 2 ) 2 ] from the solvent‐free reaction of 1,1‐dichloro‐4‐methoxy‐3‐penten‐2‐one with primary and secondary amines is reported. 1,1‐Dichloro‐4‐methoxy‐3‐penten‐2‐one was reacted with hydrazine hydrochloride, phenylhydrazine hydrochloride and semicarbazide hydrochloride to obtain 5‐dichloromethyl‐3‐methylpyrazoles. Aminoguanidine hydrochloride and 1,2‐dimethylhydrazine dihydrochloride were also reacted with 1,1‐dichloro‐4‐methoxy‐3‐penten‐2‐one to obtain 5‐dichloromethyl‐3‐methylpyrazoline and 5‐dichloromethyl‐1,2,3‐trimethyl pyrazolium chloride, respectively. All cyclocondensation reactions were performed in one‐pot procedures. J. Heterocyclic Chem., (2009).