Abstract This article presents the unexpected synthesis of 3-phenylethyl-2,4(1 H ,3 H )-quinazolinediones by means of oxidative expansion of the 3-phenylethylimino-2-indolinone ring promoted by sodium borohydride. The 1 H NMR spectroscopic patterns showed the presence of two conformational isomers in equilibrium, the first was a staggered conformation and the second was a gauche structure. The crystal structure of 3-phenylethyl-2,4(1 H ,3 H )-quinazolinedione revealed a staggered conformation with the quinazoline fragment and the phenyl ring in anti -arrangement. The molecules of quinazolinedione are associated in centrosymmetric dimers through two N H⋯O hydrogen bonds between the NH moieties and the adjacent carbonyl groups.

中文翻译：

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3-苯乙基-2,4(1 H ,3 H )-喹唑啉二酮的合成及结构分析

摘要 本文介绍了 3-苯乙基-2,4(1 H ,3 H )-喹唑啉二酮通过硼氢化钠促进的 3-苯乙基亚氨基-2-吲哚酮环氧化膨胀的意外合成。1 H NMR光谱图显示平衡中存在两种构象异构体，第一种是交错构象，第二种是gauche结构。3-苯乙基-2,4(1 H ,3 H )-喹唑啉二酮的晶体结构揭示了与喹唑啉片段和苯环反排列的交错构象。喹唑啉二酮分子通过 NH 部分和相邻羰基之间的两个 NH⋯O 氢键结合成中心对称二聚体。