Estimated Rate Constants for Hydrogen Abstraction from N-Heterocyclic Carbene−Borane Complexes by an Alkyl Radical

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• 作者：Andrey Solovyev ; Shau-Hua Ueng ; Julien Monot ; Louis Fensterbank ; Max Malacria ; Emmanuel Lacte ; Dennis P. Curran
• 刊名：Organic Letters
• 出版年：2010
• 出版时间：July 2, 2010
• 年：2010
• 卷：12
• 期：13
• 页码：2998-3001
• 全文大小：190K
• 年卷期：v.12,no.13(July 2, 2010)
• ISSN：1523-7052

文摘

Rate constants for hydrogen abstraction by a nonyl radical from 20 complexes of N-heterocyclic carbenes and boranes (NHC−boranes) have been determined by the pyridine-2-thioneoxycarbonyl (PTOC) competition kinetic method at a single concentration point. The rate constants range from <1 × 10⁴ to 8 × 10⁴ M⁻¹ s⁻¹. They show little dependence on the electronic properties of the carbene core, but there is a trend for increasing rate constants with decreasing size of the carbene N-substituents. Two promising new reagents with small N-substituents (R = Me) have been identified.