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2D Ultrafast HMBC 1H,31P: Obtaining Mechanistic Details on the Michaelis–Arbuzov Reaction

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journal contribution
posted on 16.01.2015, 00:00 by María Encarnación Fernández-Valle, Roberto Martínez-Álvarez, Dolores Molero-Vílchez, Zulay D. Pardo, Elena Sáez-Barajas, Antonio Herrera
Ultrafast NMR spectroscopy (UF-NMR) can be used to monitor chemical reactions in real time and to provide insights into their mechanisms and the nature of the intermediates formed. Here, we have developed a 2D 1H,31P UF-HMBC method and the corresponding NMR experimental setup to enable the study of a Michaelis–Arbuzov reaction at two different temperatures, 25 and 70 °C. The specific reaction studied was between triethyl phosphite and benzyl bromide to produce diethylbenzyl phosphonate. Our results show that at 70 °C the reaction takes place directly, without the detection of an intermediate by 1H,31P UF-HMBC. In contrast, at 25 °C, using zinc bromide as a catalyst, our results show the formation of benzyltriethoxy phosphonium bromide as an intermediate. The experiments again show the power of UF-NMR in mechanistic studies of reactions involving various phosphorus chemical species.