2-Amino-4H-pyran-3-carbonitriles and 2-amino-4H-pyran-3-carboxylate derivatives were synthesized under mild conditions in the presence of tungstate sulfuric acid (TSA) as a recyclable solid acid catalyst. Catalytic condensation between 3-acetylcoumarin, aromatic aldehydes, and malononitrile or ethyl cyanoacetate gave the 2-amino-4H-pyran derivatives. Tungstate sulfuric acid is a low-cost, nontoxic, and reusable catalyst, which does not require very high temperatures and good to excellent yields were obtained in all cases. The catalyst can be reused for many times without significant loss of its activity.

中文翻译：

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以钨酸硫酸为固体酸催化剂，绿色，简便，一锅法合成2-氨基-4H-吡喃衍生物

在钨酸硫酸（TSA）作为可循环使用的固体酸催化剂的条件下，在温和条件下合成了2-氨基-4 H-吡喃-3-腈和2-氨基-4 H-吡喃-3-羧酸酯衍生物。3-乙酰香豆素，芳族醛和丙二腈或氰基乙酸乙酯之间的催化缩合得到2-氨基-4 H-吡喃衍生物。钨酸硫酸是一种低成本，无毒且可重复使用的催化剂，它不需要很高的温度，在所有情况下都能获得良好的产率。该催化剂可以重复使用多次，而不会显着降低其活性。