Kinetic Study of Carbophilic Lewis Acid Catalyzed Oxyboration and the Noninnocent Role of Sodium Chloride

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• 作者：Joel S. Johnson ; Eugene Chong ; Kim N. Tu ; Suzanne A. Blum
• 刊名：Organometallics
• 出版年：2016
• 出版时间：March 14, 2016
• 年：2016
• 卷：35
• 期：5
• 页码：655-662
• 全文大小：426K
• ISSN：1520-6041

文摘

In the present study, the oxyboration reaction catalyzed by IPrAuTFA in the presence and absence of NaTFA has been examined with kinetic studies, mass spectrometry, and ¹H NMR and ¹¹B NMR spectroscopy. Data from monitoring the reactions over the temperature range from 30 to 70 °C, the catalyst range from 1.3 to 7.5 mol %, and the NaTFA additive range from 2.5 to 30 mol % suggests a mechanism that involves rate-determining catalyst generation. Data from additive studies that replaced NaTFA with NaBARF (BARF = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) or Bu₄NTFA as an alternative additive suggest that catalyst quenching from residual NaCl remaining from a one-pot substrate synthesis/reaction method is the cause of this effect, despite the low solubility of this NaCl byproduct in toluene. Material produced through an alternative, sodium chloride-free substrate synthesis exhibited faster reaction rates, consistent with a change in rate-determining step that depended on the substrate synthesis route.