An efficient synthesis of S-allyl thioimidate hydrobromide salts via coupling of thioamides with allyl bromide derivatives is described. A range of mono-, di-, and trisubstituted olefins as well as alkyl- and arylthioamides with variations in electronics are tolerated. A rapid anti-diastereoselective halocyclization of these salts provides a variety of substituted alkyl- and arylthiazolines. Initial development of an efficient enantioselective synthesis of quaternary-substituted thiazolines through the organo-catalyzed halocyclization of sulfonate thioimidate salts is also described.