Quaternization of 3-(3-butynylthio) and 3-(4-pentynyltio) substituted 1,2,4-triazines with triethyloxonium tetrafluoroborate in CH2Cl2 at room temperature occurs exclusively at N-1 yielding 3-alkynylthio-1-ethyl-1,2,4-triazinium salts, as unequivocally shown by the 13C NMR and X-ray crystallographic data. 3-Alkynylthio-1-ethyl-5-phenyl-1,2,4-triazinium salts undergo the intramolecular Diels-Alder reaction into the corresponding thieno [2,3-b]- and thiopyrano [2,3-b]pyridines under considerably milder conditions than the corresponding neutral 1,2,4-triazines.