STRUCTURE ENERGY RELATIONS FOR THE ALDOL REACTION IN NONPOLAR MEDIA
STRUCTURE ENERGY RELATIONS FOR THE ALDOL REACTION IN NONPOLAR MEDIA
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DOI：
10.1021/ja00158a047
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发表时间：
1990-01-17
影响因子：
15
通讯作者：
RIBEIRO, AA
中科院分区：
文献类型：
--
作者：
ARNETT, EM;FISHER, FJ;RIBEIRO, AA
本文对锂频哪醇盐与新戊醛在己烷中，25 ℃和在环己烷中，25 ℃和6 ℃的羟醛缩合反应进行了完整的热化学分析。在存在和不存在四氢呋喃、四甲基乙二胺和二甲氧基乙烷的情况下进行反应。反应物和产物的溶液结构通过使用依数性技术（蒸气压渗透压测定法和凝固点降低法）测量聚集度并通过使用6Li和2D 6Li-1H杂原子Overhauser增强（HOESY）NMR来确定。滴定量热法用于确定新戊醛与六聚锂频哪醇盐、四聚和二聚烯醇盐-配体络合物的反应热，以及六聚烯醇盐与配体的相互作用热。结果表明，在烃类溶液中，四聚的羟醛酸锂产物不与三种配体中的任何一种配位。给出了实验技术的完整描述，并且大部分数据已经通过两次完整和独立的重复来证实。然而，我们注意到在我们以前的通讯中报道的一个错误的，目前无法解释的值（7/=-30.19 keal/mol），该值是关于未络合的六聚锂频哪醇盐与新戊醛在己烷中在25 ℃下的羟醛缩合反应。据我们所知，本文是第一个完整的结构能量分析的aldol反应的条件下接近thosehused在现代合成。这些结果强调了在提出这一重要反应的详细机制时谨慎的重要性。
A complete thermochemical analysis is presented for the aldol reaction of lithiopinacolonate with pivalaldehyde in hexane at 25 C and in cyclohexane at 25 and 6 C. Reactions were performed in the presence and absence of tetrahydrofuran, tetramethylethylenediamine, and dimethoxyethane. Solution structures of the reactants and products were determined by using colligative property techniques (vapor pressure osmometry and freezing point depression) to measure the degrees of aggregation and by using 6Li and 2D 6Li-'H heteronuclear Overhauser enhancement (HOESY) NMR. Titration calorimetry was used to determine the heats of reaction of pivalaldehyde with the hexameric lithiopinacolonate, the tetrameric and dimeric enolate-ligand complexes, and heats of interaction of the hexameric enolate with the ligands. It is shown that the tetrameric lithium aldolate product does not complex with any of the three ligands in hydrocarbon solution. A complete description of experimental techniques is given, and most of the data have been confirmed by two complete and independent repetitions. However, attention is drawn to an erroneous, and presently unexplained value (7/=-30.19 keal/mol) reported in our previous communication for the aldol reaction of the uncomplexed hexameric lithiopinacolonatewith pivalaldehyde inhexane at 25 C. To our knowledge, the present article is the first complete structure-energy analysis of an aldol reaction under conditions approaching thoseused in modern synthesis. The results emphasize the importance of caution in proposing detailed mechanisms for thisimportant reaction.