Computational and NMR Spectroscopic Evidence for Stereochemistry-Dependent Conformations of 2,2,6,6-Tetramethylpiperidinyl-Masked 1,2-Diols

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• 作者：Ellie L. Fought ; Shreyosree Chatterjee ; Theresa L. Windus ; Jason S. Chen
• 刊名：Journal of Organic Chemistry
• 出版年：2015
• 出版时间：October 16, 2015
• 年：2015
• 卷：80
• 期：20
• 页码：9967-9972
• 全文大小：364K
• ISSN：1520-6904

文摘

2,2,6,6-Tetramethylpiperidinyl-masked 1,2-diols exhibited stereochemistry-dependent hydroxyl proton chemical shifts: ca. 7 ppm for the syn diastereomer and ca. 2 ppm for the anti diastereomer. A computational search for low energy geometries revealed that the syn isomer favors a six-membered ring hydrogen bond to nitrogen and the anti isomer favors a five-membered ring hydrogen bond to oxygen. The computed low energy conformations were found to have a large difference in hydroxyl proton shielding that was reflected in the experimental chemical shift difference. This chemical shift difference was observed in a broad range of solvents, and thus may be useful as a stereochemical probe. The stereochemistry-dependent conformation and chemical shift signature appeared to be due to a syn pentane interaction between the gem-dimethyl groups on the 2,2,6,6-tetramethylpiperidinyl moiety.