The present report describes one-pot three-component condensation of isatins, malononitrile, and 2-hydroxy-4H-pyrimido[2,1-b][1,3]benzothiazol-4-one in water–ethanol mixture at reflux to develop an efficient one-pot protocol for the synthesis of novel spiro[indole-3,4′-pyrano[2′,3′:4,5]pyrimido[2,1-b][1,3]benzothiazole] derivatives. The significant features of this protocol are short reaction times, avoidance of toxic catalysts, and provision of excellent yields, no column chromatographic purification, and use of ethanol-water as an environmentally benign solvent. The molecular structure of 4a has been supported by single-crystal X-ray diffraction.

中文翻译：

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新型螺[吲哚-3,4'-吡喃[2',3':4,5]嘧啶[2,1-b][1,3]苯并噻唑]衍生物的一锅法无催化剂合成

本报告描述了靛红、丙二腈和 2-羟基-4H-嘧啶基[2,1-b][1,3]苯并噻唑-4-one 在水-乙醇混合物中回流的一锅三组分缩合反应，以开发一种用于合成新型螺[吲哚-3,4'-吡喃并[2',3':4,5]嘧啶[2,1-b][1,3]苯并噻唑]衍生物的高效一锅法。该协议的显着特点是反应时间短、避免使用有毒催化剂、提供出色的收率、无柱色谱纯化以及使用乙醇-水作为环境友好型溶剂。4a 的分子结构已得到单晶 X 射线衍射的支持。