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首页> 外文期刊>Acta crystallographica. Section C, Structural chemistry. >Zwitterionic and free forms of arylmethyl Meldrum's acids
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Zwitterionic and free forms of arylmethyl Meldrum's acids

机译：两性离子和游离形式的芳基甲基Meldrum酸

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摘要

C-Alkyl (including C-arylmethyl) derivatives of Meldrum's acids are attractive building blocks in organic synthesis, mainly due to the unusually high acidity of the resulting compounds. Three examples, namely 5-[4-(diethylamino)benzyl]-2,2-dimethyl-1,3-dioxane-4,6-dione, C17H23NO4, (I), 2,2-dimethyl-5-(2,4,6-trimethoxybenzyl)-1,3-dioxane-4,6-dione, C16H20O7, (II), and 5-(4-hydroxy-3,5-dimethoxybenzyl)-2,2-dimethyl-1,3-dioxane-4,6-dione, C15H18O7, (III), have been synthesized, characterized by NMR and IR spectroscopy, and studied by single-crystal X-ray structure analysis. The nature of the different substituents resulted in remarkable differences in both the molecular conformations and the crystal packing arrangements. The presence of a substituent with a basic centre in compound (I) leads to the formation of an inner salt accompanied by drastic changes in the conformation of the 1,3-dioxane-4,6-dione fragment. By virtue of strong N—H...O hydrogen bonds, the residues are assembled into infinite chains with the graph-set descriptor C(10). Compound (II) contains methoxy groups in both the ortho- and para-positions of the arylmethyl fragment. Because of the absence of classical hydrogen-bond donors in this structure, the crystal packing is controlled by van der Waals forces and weak C—H...O interactions. Compound (III) contains methoxy groups in both meta-positions and a hydroxy group in the para-position. Supramolecular tetrameric synthons which comprise hydrogen-bonded dimers associated into tetramers through π–π interactions of overlapping benzene rings were observed.
机译：Meldrum酸的C-烷基（包括C-芳基甲基）衍生物是有机合成中有吸引力的结构单元，主要是由于所得化合物的酸度异常高。三个实例，即5- [4-（二乙氨基）苄基] -2,2-二甲基-1,3-二恶烷-4,6-二酮，C17H23NO4，（I），2,2-二甲基-5-（2， 4,6-三甲氧基苄基）-1,3-二恶烷-4,6-二酮，C16H20O7，（II）和5-（4-羟基-3,5-二甲氧基苄基）-2,2-二甲基-1,3-已合成了二恶烷-4,6-二酮C15H18O7（III），并通过NMR和IR进行了表征，并通过单晶X射线结构分析进行了研究。不同取代基的性质导致分子构象和晶体堆积排列上的显着差异。化合物（I）中具有碱性中心的取代基的存在导致内盐的形成，伴随着1，3-二恶烷-4，6-二酮片段的构象的急剧变化。凭借强大的NH ... O氢键，残基通过图集描述符C（10）组装成无限链。化合物（II）在芳基甲基片段的邻位和对位均含有甲氧基。由于该结构中不存在经典的氢键供体，因此晶体堆积受范德华力和弱的CH-O ... O相互作用控制。化合物（III）在间位均含有甲氧基，在对位均含有羟基。观察到超分子四聚体合成子，其中包括氢键合的二聚体，通过重叠的苯环的π-π相互作用与四聚体缔合。

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