Coumarin-3-carboxylic acids represent a class of natural occurring and semi-synthetic products with valuable reported pharmacological activities. In this Letter a new and improved method for the chemical synthesis of the title compounds is described. Coumarin-3-carboxylic acids have been synthesized in good to excellent yields under microwave irradiation and solvent-free conditions from differently substituted 2-hydroxybenzaldehydes or 2 hydroxyacetophenones and Meldrum’s acid as starting materials in the presence of Yb(OTf)3 hydrate 5% mol as the catalyst.

中文翻译：

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三氟f酸催化微波辅助合成香豆素-3-羧酸

香豆素-3-羧酸代表一类天然的和半合成的产品，具有有价值的药理活性。在这封信中，描述了一种新的和改进的化学合成标题化合物的方法。在5％mol的Yb（OTf）3水合物存在下，在微波辐射和无溶剂条件下，以不同取代的2-羟基苯甲醛或2个羟基苯乙酮和Meldrum酸为起始原料，合成了香豆素3-羧酸。作为催化剂。