Regiospecific Synthesis of 5-Trichloromethyl-1H-Pyrazole and 1HPyrazole-5-Carboxylic Ester Derivatives

Alex   F.C.   Flores; Sidnei      Moura; Favero   R.   Paula; Ernani      Pinto; Pablo      Machado; Marcos   A.P.   Martins

doi:10.2174/157017808783743984

Abstract

Reaction of 1,1,1-trichloro-4-methoxy-3-penten-2-one (1) with hydrazines (2a-h) (NH2NHR, R = H, Me, t-Bu, Ph, 4-NO2-C6H4, C6F5, CO2Me, CONH2) under differing conditions regiospecifically affords different pyrazole derivatives, 3-methyl-5-trichloromethyl-5-hydroxy-4,5-dihydropyrazoles (3a, d-h), 3-methyl-5-trichloromethyl-1H-pyrazoles (4a,b,d-g) and 5-carboxyethyl-3-methyl-1H-pyrazoles (5a-e). The structural assignments were based on the analysis of their 1H/13C NMR and ESI-MS data.

Keywords: Pyrazoles, trichloromethyl-1H-pyrazoles, 1, 1, 1-trichloro-4-alkoxy-3-alken-2-ones, cyclocondensation [CCC +NN]

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Letters in Organic Chemistry

Title: Regiospecific Synthesis of 5-Trichloromethyl-1H-Pyrazole and 1HPyrazole-5-Carboxylic Ester Derivatives

Volume: 5 Issue: 2

Author(s): Alex F.C. Flores, Sidnei Moura, Favero R. Paula, Ernani Pinto, Pablo Machado and Marcos A.P. Martins

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Keywords: Pyrazoles, trichloromethyl-1H-pyrazoles, 1, 1, 1-trichloro-4-alkoxy-3-alken-2-ones, cyclocondensation [CCC +NN]

Abstract: Reaction of 1,1,1-trichloro-4-methoxy-3-penten-2-one (1) with hydrazines (2a-h) (NH2NHR, R = H, Me, t-Bu, Ph, 4-NO2-C6H4, C6F5, CO2Me, CONH2) under differing conditions regiospecifically affords different pyrazole derivatives, 3-methyl-5-trichloromethyl-5-hydroxy-4,5-dihydropyrazoles (3a, d-h), 3-methyl-5-trichloromethyl-1H-pyrazoles (4a,b,d-g) and 5-carboxyethyl-3-methyl-1H-pyrazoles (5a-e). The structural assignments were based on the analysis of their 1H/13C NMR and ESI-MS data.

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Flores F.C. Alex, Moura Sidnei, Paula R. Favero, Pinto Ernani, Machado Pablo and Martins A.P. Marcos, Regiospecific Synthesis of 5-Trichloromethyl-1H-Pyrazole and 1HPyrazole-5-Carboxylic Ester Derivatives, Letters in Organic Chemistry 2008; 5 (2) . https://dx.doi.org/10.2174/157017808783743984