We report the first example of highly enantioselective synthesis of structurally diverse chiral dithioketalsviaasymmetric sulfenylation of various types of S-based nucleophiles, catalyzed by a cheap cinchona alkaloid derivative, dihydroquinine.
The Horner–Wittig reaction of (1a,b) with phenyl isocyanate or dehydration of amides (4c–g) gave the C-sulphenylketenimines (3a–g) in moderate yields. Thermolysis of (3b) gave 2-ethoxy-3-phenylthioquinolin-4-ol (7)via intramolecular cyclization, and the reactions of (3e) and (3f) with CN-diphenylnitrone gave 3-methylthioindolones (10a) and (10b), respectively.