1.4- Thiazines synthesis

An example of 1,2-thiazine synthesis in which the creation of the S—N bond is the final step is the thermolysis of azides (246) to afford the expected lX.4-l,2-thiazines (247) (86JCS(Pl)483). 

In order to classify the types of reactions that can be used for 1,3-thiazine synthesis, Cain and Warrener (70AJC51) chose a way similar to that proposed for pyrimidines by Kenner and Todd (57M12). 

Chlorinated thiazines, synthesis and dehalogenation of 85S586. Dihydrothiazine N-oxides in synthesis of unusual sugars 86BSB1021. Oxo- and thioxo-l,3-thiazines, synthesis and properties 86KGS3. Phenothiazines, IR spectra of 83H(20)283. 

There are a few examples of 1,2-thiazine synthesis of this type which are of importance. The most noteworthy is the preparation of 4-hydroxy-2/f-l,2-benzothiazine 1,1-dioxides (199) from the benzisothiazolinone (200) <81AHC(28)73>. This general procedure can be extended to the preparation of 2-alkyl-4-hydroxybenzothiazines. The treatment of A-methylsaccharin (201) and an alkyl chloro-acetate with NaH in DMSO or DMF affords a 76% yield of the 1,2-benzothiazine (202) (Scheme 39) <83JOC3601, 86CCC 1113,86FES819>. 

Synthesis. The method of synthesis for Methylene Blue described in reference 14 is stiU the stepwise method of choice for thiazine dyes. /V,/V-Dimethy1-y-pheny1ene diamine [99-98-9], CgH22N2, reacts with sodium thiosulfate [7772-98-7] to form the thiosulfonic acid which condenses with /V, /V-dimetby1 ani1 ine [121 -69-7], CgH N, in the presence of sodium dichromate [10588-01-9] to the indamine, then with copper sulfate [18939-61 -2] and sodium dichromate to Methylene Blue (26). 

Scientists at Merck developed a cephalosporin synthesis based on the addition of azidoacetyl chloride to 1,3-thiazines (56). Although this gives the incorrect 7a -epimer (57), it could be equilibrated to a mixture of 7-amino epimers (see Section 5.10.3.3) from which the desired 7/3-isomer could be separated and further elaborated to cephalosporins (B-82MI51001). 

Benzofuro[3,2-c]pyrroles reduction, 4, 1079 Benzofuro[3,2-6]pyrylium salts synthesis, 4, 995 Benzofuro[2,3-c][l, 2]thiazine... 

Imidazo[4,5-fi][l,3]thiazine, 6-amino-2-bromo-l,5-dihydro-synthesis, 5, 664... 

Indolo[2,3-d][l,3]thiazine-2,4-dithione formation, 4, 299 Indolothiazines synthesis, 4, 519 Indoloyl azides Curtius rearrangement, 4, 288 Indolyl anions acylation, 4, 232 alkylation, 4, 235 Michael-type additions, 4, 236 Indomethacin... 

Synthesis, stereochemistry, and transformations of cyclopenta-, cyclohexa-, cyclohepta-, and cycloocta-annelated 1,3-thiazines 98AHC(69)349. 

Thiazepinones, as photolytic products 883 Thiazine 1-oxides, synthesis of 323, 352 Thiene dioxides formula of 382 synthesis of 469 Thiene oxides formula of 382 synthesis of 469... 

The mechanism for the synthesis of 3-aminopyrroles by ring transformation-desulphurisation of substituted 2-methylisothiazolium salts was investigated and evidence for the intermediacy of 3-aIkylideneaminothioacrylamides (30) and 27f-l,3-thiazines (31) obtained <96JCS(P1)2239>. 

The third chapter deals with leuco derivatives of the oxazine, thiazine, and phenazine dyes, and is written by Tran Van Thien, who has had many years experience in photoimaging at the 3M Research Center, Harlow. His industrial experience in leuco dyes has enabled him to produce a collation of material impossible to find elsewhere in a single review, and again recipes for the synthesis of representative examples abound. Consideration is also given to the numerous applications of these molecules in thermal and photo-imaging systems. 

Scheme 10.17. Microwave-assisted solvent-free synthesis of 1,3-thiazines.

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