Determining (Finally) the Structure of an Elusive Reaction Intermediate

Enolonium species/iodo(III)enolates of carbonyl compounds have been suggested to be intermediates in a wide variety of hypervalent iodine induced chemical transformations of ketones, including C-O, C-N, C-C and C-halide bond formation, but they have never been characterized. We report that these elusive umpoled enolates may be made as discrete species that are stable for several minutes at -78°C, and report the first spectroscopic identification of such species. Our results open up chemical space for designing a variety of new transformations. So how did we conclusively identify these species? By calculating the NMR spectra of the various potential intermediates and comparing to the experimental spectra, of course.

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[1] Shlomy Arava, Jaypraksh N. Kumar, Shimon Maksymenko, Mark A. Iron, Keshaba N. Parida, Peter Fristrup and Alex M. Szpilman Angewandte Chemie International Edition, 2017, 56, 2599-2603 (DOI: 10.1002/anie.201610274).