Beckmann rearrangement of ketoximes promoted by cyanuric chloride and dimethyl sulfoxide under a mild condition. (19th January 2021) - Ma, Ruonan
Graphical abstract: Beckman rearrangements of ketoximes with a promoter of cyanuric chloride/DMSO was optimized and developed to afford fourteen amides efficiently under mild conditions. A dimethyl alkoxysulfonium intermediate was confirmed as an efficient promoter and a plausible mechanism of the rearrangement is depicted. Highlights: Beckmann rearrangement of ketoximes mediated by TCT/DMSO is investigated. The approach of rearrangement is optimized to mild conditions. Fourteen amides are afforded in moderate to high yields. An active dimethyl alkoxysulfonium intermediate is confirmed by mass analysis. Mechanistic insights into the approach of rearrangement are depicted. Abstract: Synthesis of amides via Beckmann rearrangement of ketoximes promoted by cyanuric chloride (TCT)/DMSO under mild conditions has been reported. Conditions of the Beckmann rearrangement, e.g., solvents, the ratios of TCT/DMSO, and the temperature, were investigated using diphenylmethanone oxime as a substrate. The optimized conditions were adopted to afford fourteen amides with yields ranging from 20% to 99%. A plausible mechanism involving an active dimethyl alkoxysulfonium intermediate was proposed according to the mass spectrometry analysis. To our best knowledge, this is the first case of study on Beckmann rearrangement of ketoximes promoted by TCT/DMSO under a mild condition to afford amides efficiently.