Synthesis of α-Keto-Imides via Oxidation of Ynamides

A de novo preparation of α-keto-imides via ynamide oxidation is described. With a number of alkyne oxidation conditions screened, a highly efficient RuO2−NaIO4 mediated oxidation and a DMDO oxidation have been identified to tolerate a wide range of ynamide types. In addition to accessing a wide variety of α-keto-imides, the RuO2−NaIO4 protocol provides a novel entry to the vicinal tricarbonyl motif via oxidation of push−pull ynamides, and imido acylsilanes from silyl-substituted ynamides. Chemoselective oxidation of ynamides containing olefins can be achieved by using DMDO, while the RuO2−NaIO4 protocol is not effective. These studies provide further support for the synthetic utility of ynamides.