Divergent Multicomponent Tandem Palladium‐Catalyzed Aminocarbonylation‐Cyclization Approaches to Functionalized Imidazothiazinones and Imidazothiazoles

The reactivity of 2‐(prop‐2‐ynylthio)imidazoles under PdI 2 /KI‐catalyzed oxidative aminocarbonylation conditions has been studied. Under relatively mild conditions, 0.33–1 mol % of catalyst at 100 °C in MeCN and under 20 atm (at 25 °C) of a 4:1 mixture of CO/air, and in the presence of an equimolar amount of a secondary nucleophilic amine, substrates that are unsubstituted or bear a single substituent on the imidazole ring were converted directly in a multicomponent fashion into functionalized imidazothiazinones. This transformation occurred through a new auto‐tandem catalysis process that involves two concatenated catalytic cycles both catalyzed by PdI 2 : oxidative aminocarbonylation of the terminal triple bond/cyclocarbonylation. However, in the presence of an excess of secondary amine, 4,5‐disubstituted substrates led selectively to functionalized imidazothiazoles through an oxidative aminocarbonylation/conjugate addition process.