First synthesis of stable 5-alkyl- or 4,5-dialkyl-substituted 1,2-thiazinylium salt

5-t-Butyl-1,2-thiazinylium 6c and rigid 5,8-ethano-5,8-dihydrobenzo[d]-1,2-thiazinylium salts 17 without conjugated stabilization with the aromatic ring at the 4- or 5-position of the thiazine ring have been successfully obtained as crystals.