A chemoselective route to thiazolines and thiazines has been devised by heterocyclization of viable α-N-hydroxyimino-β-oxodithioesters with 2-chloroethylamine hydrochloride/3-chloropropylamine hydrochloride, which does not require metals or additives and proceeds at 0-60 °C. The overall transformation involves base mediated intramolecular cyclization of α-N-hydroxyimino-β-oxodithioesters to 4-membered oxazete-4-thione intermediates followed by coupling with chloroalkyl amines via tandem ring cleavage and CÀ N/CÀ S bonds formation enabling the construction of thiazolines/thiazines in one-pot. This strategy allows broadening the arsenal of synthetic methods to obtain N,S-heterocycles utilizing substrates prepared according to reported procedures.