Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States.
J Org Chem. 2016 Nov 18;81(22):11057-11064. doi: 10.1021/acs.joc.6b02067. Epub 2016 Oct 17.
Enolization of O-methyl hydroxamic acids (Weinreb amides) in tetrahydrofuran solution with lithium diisopropylamide affords predominantly tetrameric enolates. Aryl substituents on the enolates promote deaggregation. The aggregation states are assigned by using the method of continuous variation in conjunction with Li NMR spectroscopy. Decoalescence of the tetramer resonance below -100 °C shows considerable spectral complexity attributed to isomerism of the methoxy-based chelates. Density functional theory calculations were used to examine the consequences of the bite angle of five-membered chelates in cubic tetramers and resulting solvation numbers that were higher than anticipated.
在四氢呋喃溶液中，用二异丙基氨基锂使 O-甲基羟肟酸（Weinreb 酰胺）烯醇化，主要得到四聚体烯醇化物。烯醇化物上的芳基取代基促进解聚。通过连续变化法结合 Li NMR 光谱法来确定聚合状态。在-100°C 以下，四聚体共振的分解表明，由于甲氧基配位螯合物的异构化，光谱复杂性相当大。密度泛函理论计算用于研究五元螯合的咬合角度对立方四聚体的影响，以及由此产生的溶剂化数高于预期。
