Journal
SYNLETT
Volume -, Issue 11, Pages 1673-1678Publisher
GEORG THIEME VERLAG KG
DOI: 10.1055/s-2008-1078482
Keywords
enones; cyclizations; regioselectivity; pyrazoles; heterocycles
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Funding
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq/PADCT)
- Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS)
- CNPq
- CAPES
- FAPERGS
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A series of 4-substituted 1H-pyrazole-5-carboxylates was prepared from the cyclocondensation reaction Of Unsymmetrical enaminodiketones [RC(O)C(=CNMe(2))C(O)CO(2)Et, where R = Ph, 4-MeOC(6)H(4), 4-ClC(6)H(4), 4-FC(6)H(4), 4-O(2)NC(6)H(4), thien-2-yl, benzofur-2-yl, CCl(3) and CF(3)] with tert-butylhydrazine hydrochloride or carboxymethylhydrazine. The compounds were obtained regiospecifically and in good to excellent yields (73-94%). In addition, 5-carboxyethyl-1-(1, 1-dimethylethyl)-1H-pyrazole-4-carboxylic acid was synthesized from regiospecific conversion of ethyl 4-(2,2,2-trichloroacetyl)-1-(1, 1-dimethylethyl)-1H-pyrazole-5-carboxylate. The carbonyl substitution reaction was regiospecific for the trichloroacetyl group and did not affect the ester group.
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