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

Depending on their structures, imines are able to undergo either olefination or vicinal difunctionalization with various a-(benzothiazol-2-ylsulfonyl) carbonyl compounds in the absence of external bases. The olefination reaction of aromatic imines with alpha-(benzothiazol-2-ylsulfonyl) carbonyl compounds proceeds smoothly in tetrahydrofuran at 70 degrees C to give structurally diverse alpha, beta-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 alpha,beta-unsaturated imines are subjected to regiospecific vicinal difunctionalization with alpha-(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.