2-Aryl-3,5-dimethyl-1,1-dioxo-1,2-thiazine-4 and 6-carbaldehydes (4 and 5) show as "masked 1,3- or unsaturated 1,5-dicarbonyl compounds" as well as "2,3-bridged crotonaldehydes" an interesting reactivity in a wide variety of ring transformation and cyclization reactions. By ring transformation reactions of 4 and 5 with 1,2-diamine, hydroxyl amine, ammonia and ethylamine, substituted heterocycles such as 2,3-dihydro-1,4-diazepines, isoxazoles, chloropyridine and aceto-1,1-dioxothiazine could been synthesized. In addition, the masked dicarbonyl compounds 4 and 5 could been used for cyclization reactions with suitable electrophiles like sulphur, acetylenedicarboxylic acid diesters and donator-acceptor-substituted ethylenes in presence of triethylamine to prepare novel bicyclic heterocycles such as thienothiazines, benzothiazines and tetrahydrobenzothiazines on an easy way. Different NMR technologies were used for the structural confirmation of the compounds beside the mass spectroscopy. The obtained 1,4-diazepines interact with silver ions in the form of silver nitrate forming complexes, soluble in acetonitrile. The application of the 1,4-diazepines as diazepinium bromides in silver halogenide emulsions leads to an improved sensitivity-fog-relation what could be of practical importance. The synthesized heterocycles are of interest as potentially biologically active compounds.