Lithium Hexamethyldisilazide-Mediated Enolization of Acylated Oxazolidinones: Solvent, Cosolvent, and Isotope Effects on Competing Monomer- and Dimer-Based Pathways

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• 作者：Gabriel J. Reyes-Rodríguez ; Russell F. Algera ; David B. Collum
• 刊名：Journal of the American Chemical Society
• 出版年：2017
• 出版时间：January 25, 2017
• 年：2017
• 卷：139
• 期：3
• 页码：1233-1244
• 全文大小：683K
• ISSN：1520-5126

文摘

Lithium hexamethyldisilazide (LiHMDS)-mediated enolization of (+)-4-benzyl-3-propionyl-2-oxazolidinone in THF–hydrocarbon mixtures shows unusual sensitivity to the choice of hydrocarbon cosolvent (hexane versus toluene) and to isotopic labeling. Four mechanisms corresponding to monosolvated monomers, trisolvated dimers, octasolvated monomers, and octasolvated dimers were identified. Even under conditions in which the LiHMDS monomer was the dominant observable form, dimer-based metalation was significant. The mechanism-dependent isotope and cosolvent effects are discussed in the context of ground-state stabilization and transition-state tunneling.