Stereoselective Olefination and Regiospecific Vicinal Difunctionalization of Imines with α‐(Benzothiazol‐2‐ylsulfonyl) Carbonyl Compounds

Abstract

AbstractDepending on their structures, imines are able to undergo either olefination or vicinal difunctionalization with various α‐(benzothiazol‐2‐ylsulfonyl) carbonyl compounds in the absence of external bases. The olefination reaction of aromatic imines with α‐(benzothiazol‐2‐ylsulfonyl) carbonyl compounds proceeds smoothly in tetrahydrofuran at 70 °C to give structurally diverse α,β‐unsaturated esters, amides, and ketones in good to excellent yields and with extremely high (E) selectivity. In contrast, the carbon–nitrogen double bonds of cyclic imines and the carbon–carbon double bonds of α,β‐unsaturated imines are subjected to regiospecific vicinal difunctionalization with α‐(benzothiazol‐2‐ylsulfonyl) carbonyl compounds under the same reaction conditions to give a variety of benzothiazole derivatives in good to excellent yields. It is noteworthy that the benzothiazole moiety is present in a number of antitumor agents and bioluminescent molecules. In addition, plausible reaction pathways have been proposed to account for these transformations, and these are substantially supported by ESI‐MS analysis of the reaction mixtures.