Lithium Enolates Derived from Pyroglutaminol: Aggregation, Solvation, and Atropisomerism

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• 作者：Michael J. Houghton ; Naomi A. Biok ; Christopher J. Huck ; Russell F. Algera ; Ivan Keresztes ; Stephen W. Wright ; David B. Collum
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：May 20, 2016
• 年：2016
• 卷：81
• 期：10
• 页码：4149-4157
• 全文大小：606K
• 年卷期：0
• ISSN：1520-6904

文摘

Lithium enolates derived from protected pyroglutaminols were characterized by using ⁶Li, ¹³C, and ¹⁹F NMR spectroscopies in conjunction with the method of continuous variations. Mixtures of tetrasolvated dimers and tetrasolvated tetramers in different proportions depend on the steric demands of the hemiaminal protecting group, tetrahydrofuran concentration, and the presence or absence of an α-fluoro moiety. The high steric demands of the substituted bicyclo[3.3.0] ring system promote dimers to an unusual extent and allow solvents and atropisomers in cubic tetramers to be observed in the slow-exchange limit. Pyridine used as a ⁶Li chemical shift reagent proved useful in assigning solvation numbers.