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

• Published in: Journal of organic chemistry Vol. 80; no. 2; pp. 799 - 805
• Main Authors: Fernández-Valle, María Encarnación, Martínez-Álvarez, Roberto, Molero-Vílchez, Dolores, Pardo, Zulay D, Sáez-Barajas, Elena, Herrera, Antonio
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 16.01.2015
• Subjects: Benzyl Compounds - chemical synthesis; Benzyl Compounds - chemistry; Magnetic Resonance Spectroscopy; Molecular Structure; Organophosphonates - chemistry; Temperature
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo502253p

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.