Palladium‐Catalyzed Carbonylative Multicomponent Synthesis of Functionalized Benzimidazothiazoles

Abstract

AbstractThe reactivity of 2‐(prop‐2‐ynylthio)‐1 H‐benzo[d]imidazoles and their corresponding hydrobromide salts under PdI2/KI‐catalyzed oxidative aminocarbonylation conditions has been studied. It is found that 2‐prop‐2‐ynylsulfanyl‐3 H‐benzimidazolium salts, when allowed to react with amines, carbon monoxide, and oxygen, under the catalytic action of PdI2 (1 mol %) in conjunction with KI (1 equiv), under suitable conditions (80 °C and 20 atm of a 4:1 mixture of CO/air, in MeCN, and in the presence of a six‐fold excess of amine, for 15 h), could be selectively converted into 2‐benzo[4,5]imidazo[2,1‐b]thiazol‐3‐yl‐N,N‐dialkylacetamides in 60–78 % yields, through an oxidative aminocarbonylation/heterocyclization process. The structure of a representative product, 2‐benzo[4,5]imidazo[2,1‐b]thiazol‐3‐yl‐1‐pyrrolidin‐1‐ylethanone, was confirmed by X‐ray diffraction analysis.