A three-component condensation of cyclic enaminones, phenylglyoxal hydrate, and ethyl cyanoacetate in EtOH gave a number of 4,5,6,7-tetrahydroindole functional derivatives. The corresponding intermediates, 2,3,4,5,6,7-hexahydroindoles, are formed under mild conditions. Under more severe conditions (heating under reflux in DMF), cleavage of the ethoxycarbonyl group takes place.

中文翻译：

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环状烯氨基酮，水合苯乙二醛和氰基乙酸乙酯的三组分缩合

环状烯胺酮，苯乙二醛水合物和氰基乙酸乙酯在EtOH中的三组分缩合得到许多4,5,6,7-四氢吲哚官能衍生物。相应的中间体2,3,4,5,6,7-六氢吲哚在温和条件下形成。在更严格的条件下（在DMF中加热回流），乙氧基羰基发生裂解。