A Novel Route to 4-Oxy/thio substituted-1H-pyrazol-5(4H)-ones via Efficient Cross-Claisen Condensation

[摘要]：alpha-Oxy/thio substituted beta-keto esters were synthesized through an efficient cross-Claisen condensation of oxy/thio substituted acetic acid ethyl esters with acid chlorides, which in turn converted in situ into 4-oxy/thio substituted-1H-pyrazol-5(4H)-ones by the addition of hydrazine and its derivatives. This method has been found to be extremely fast, general, and useful toward the synthesis of inaccessible pyrazolones and synthetically demanding 4-oxy/thio substituted pyrazolones.

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