Brominated Trihalomethylenones as Versatile Precursors to 3‐Ethoxy, ‐Formyl, ‐Azidomethyl, ‐Triazolyl,and 3‐Aminomethyl Pyrazoles |
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Authors: | Marcos A. P. Martins Adilson P. Sinhorin Clarissa P. Frizzo Lilian Buriol Elisandra Scapin Nilo Zanatta Helio G. Bonacorso |
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Affiliation: | 1. Núcleo de Química de Heterociclos, Departamento de Química, Universidade Federal de Santa Maria, , 97105‐900 Santa Maria, Rio Grande do Sul, Brazil;2. Instituto Universitário Norte Mato Grossense, Universidade Federal de Mato Grosso, , 78550000 Sinop, Mato Grosso, Brazil;3. Laboratório de Química, Coordena??o de Engenharia Ambiental, Universidade Federal do Tocantins, , Palmas, Tocantins, Brazil |
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Abstract: | 5‐Bromo[5,5‐dibromo]‐1,1,1‐trihalo‐4‐methoxy‐3‐penten[hexen]‐2‐ones are explored as precursors to the synthesis of 3‐ethoxymethyl‐5‐trifluoromethyl‐1H‐pyrazoles from a cyclocondensation reaction with hydrazine monohydrate in ethanol. 3‐Ethoxymethyl‐carboxyethyl ester pyrazoles were formed as a result of a substitution reaction of bromine and chlorine by ethanol. The dibrominated precursor furnished 3‐acetal‐pyrazole that was easily hydrolyzed to formyl group. In addition, brominated precursors were used in a nucleophilic substitution reaction with sodium azide to synthesize the 3‐azidomethyl‐5‐ethoxycarbonyl‐1H‐pyrazole from the reaction with hydrazine monohydrate. These products were submitted to a cycloaddition reaction with phenyl acetylene furnishing the 3‐[4(5)‐phenyl‐1,2,3‐triazolyl]5‐ ethoxycarbonyl‐1H‐pyrazoles and to reduction conditions resulting in 3‐aminomethyl‐1H‐pyrazole‐5‐carboxyethyl ester. The products were obtained by a simple methodology and in moderate to good yields. |
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