It is shown that (2E,6E)‐2,6‐bis(chloromethylidene)‐N‐organyl thiomorpholine 1‐oxides and (2E,6E)‐2,6‐bis(chloromethylidene)‐1,4‐dithiane 1,1,4,4‐tetraoxides, unlike unoxidized analogs, (2E,6E)‐2,6‐bis(chloromethylidene)‐N‐organyl thiomorpholines, and (2E,6E)‐2,6‐bis(chloromethylidene)‐1,4‐dithiane, easily undergo stereoselective nucleophilic vinylic substitution reactions with such chalcogen‐containing nucleophiles as sodium 1‐butanethiolate, arenethiolates, and benzeneselenolate to afford previously unknown (2E,6E)‐2,6‐bis(organylchalogenylmethylidene)‐N‐organyl thiomorpholine 1‐oxides and (2E,6E)‐2,6‐bis(organylchalogenylmethylidene)‐1,4‐dithiane 1,1,4,4‐tetraoxides in high yields. The structures of the heterocycles formed have been confirmed by 1H, 13C NMR, and mass spectrometry data.