Regioselective synthesis of N1-substituted-4-nitropyrazole-5-carboxylates via the cyclocondensation of ethyl 4-(dimethylamino)-3-nitro-2-oxobut-3-enoate with substituted hydrazines

Abstract

A simple and expeditious method for the regioselective synthesis of N1-substituted-4-nitropyrazole-5-carboxylates was developed. The method involves cyclocondensation of ethyl 4-(dimethylamino)-3-nitro-2-oxobut-3-enoate with a series of monosubstituted hydrazines to give N1-substituted-4-nitropyrazole-5-carboxylates with...

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“…Amination of commercially available 34 using Boc-hydrazine followed by deprotection provided compound 36, which was condensed with 1-(dimethyl-amino)-2-nitro ethylene to provide substituted pyrazole 37 as a single isomer. 22 The nitro group was reduced, and the resulting amine 38 was condensed with bismethyl carbamate thiourea, furnishing the pyrazolo-pyrimidine core with pendant benzyl ester 39. This compound served as a common intermediate for modifications at both C-7 and the benzylamine positions for the generation of compounds in Tables 1 and 2.…”

“…The synthetic route for compound 20 is outlined in Scheme . Amination of commercially available 34 using Boc-hydrazine followed by deprotection provided compound 36 , which was condensed with 1-(dimethyl-amino)-2-nitro ethylene to provide substituted pyrazole 37 as a single isomer . The nitro group was reduced, and the resulting amine 38 was condensed with bismethyl carbamate thiourea, furnishing the pyrazolo-pyrimidine core with pendant benzyl ester 39 .…”