Mechanistic Study on Selenium- and Sulfur-Mediated Isomerization of Hydroxamic Acids.

An in-depth computational study reveals the intriguing mechanism of the recently reported isomerization of hydroxamic acids into para-aminophenols catalyzed by phenylselenyl bromide under mild conditions. The computations not only align with the reported experimental data, effectively explaining observed phenomena such as para-selectivity but also shed light on crucial aspects of the reaction mechanism that establish limitations on the scope of the studied rearrangement. Additionally, a joint theoretical/experimental study was performed to examine the potency of the phenylsulfenyl bromide to mediate the reaction under the same conditions.

Redox-Neutral Selenium-Catalysed Isomerisation of para-Hydroxamic Acids into para-Aminophenols.

A selenium-catalysed para-hydroxylation of N-aryl-hydroxamic acids is reported. Mechanistically, the reaction comprises an N-O bond cleavage and consecutive selenium-induced [2,3]-rearrangement to deliver para-hydroxyaniline derivatives. The mechanism is studied through both 18 O-crossover experiments as well as quantum chemical calculations. This redox-neutral transformation provides an unconventional synthetic approach to para-aminophenols.

Chemoselective Alpha-Deuteration of Amides via Retro-ene Reaction.

A synthetically convenient approach for the direct α-deuteration of amides is reported. This mechanistically unusual process relies on a retro-ene-type process, triggered by the addition of deuterated dimethyl sulfoxide to a keteniminium intermediate, generated through electrophilic amide activation. The transformation displays broad functional-group tolerance and high deuterium incorporation.