Compounds Containing a Six-Membered Ring with Two Hetero Atoms from Groups V and VI, respectively of the Periodic Table: Oxazines, Thiazines and their Analogues

This chapter discusses the nomenclature, general methods of synthesis, properties, typical reactions and stereochemical aspects of the oxazines, benzoxazines, phenoxazines, thiazines, benzothiazines, and phenothiazines and their derivatives. Oxazines are studied as 1,2-Oxazines, 1,3-Oxazines, 1,4-Oxazines and related compounds, such as morpholines and morpholones. Nominally there are nine possible benzoxazines; some are readily interconverted by tautomerism. These include 1,2-Benzoxazines, 1,3-Benzoxazines, 1,4-Benzoxazines and their hydro derivatives. The study of phenoxazine is important because some of its derivatives are highly colored and are used as dyes and also because certain phenoxazines show pharmacological activity. The simple derivatives of phenoxazines include the nitrophenoxazines, aminophenoxazines, 3-methoxyphenoxazines, phenoxazinecarboxylic acids, halogenophenoxazines, N-alkylphenoxazines and N-arylphenoxazines, acylphenoxazines, phenoxazinones and phenoxazonium salts, naturally occurring phenoxazine derivatives, such as actinomycins, cinnabarine and so on, benzophenoxazines and benzophenoxazinones. The isomeric forms of thiazines, having one sulfur and one nitrogen atom in a six-membered ring, and their hydro- and benzo- derivatives correspond with structures in the oxazine series, and are named and numbered in the same way. They include 1,2-thiazines and their hydro derivatives, 1,3-thiazines and related compounds, 1,4-thiazines, and their hydro derivatives. Phenothiazines represent an important class of drug substances, which show activity against numerous disorders. Some examples include phenothiazine homologs, halogenophenothiazines, nitrophenothiazines, aminophenothiazines and so on.