1.3- Thiazine-2,6 -dithiones

Some other pyrimidine syntheses which have been reported during the last year include ring transformations of 1-thiocarbamoyt 2-azetidinones (160), 1,3-thiazine-2,6-dithiones (l6l)... 

The thiazine dithiones also react with hydrazine, hydroxylamine, semi-carbazide, and thiosemicarbazide. Hydrazine gives 3-aminopyrimidine-2,4-dithiones (214) (Scheme 87) [80JCR(S)148]. Thiosemicarbazide reacts in the same way as diamines to give [l,2,4]triazolo[l,5-a]pyrimidines (215) (Scheme 88). 

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... 

The solid-state structures of the benzo derivatives (Z)-4-benzylidene-6,8-dichloro-4//-benzo[, ( )-4-(3,4-dichlorobenzylidene)-2-methyl-4//-benzo[< ][l,3]thiazine 20 <2004JOC4545>, and 7-amino-l/7-benzoM[l,3]thiazine-2,4-dithione 21 <2005AXEo387> have been determined. As expected, they possess planar structures, and the thiazine-2,4-dithione 21 molecules pack in the solid state through amino-thione hydrogen bonds <2005AXEo387>. 

Secondary amines (diethylamine, piperidine, or morpholine) attack the l,3-thiazine-2,6-dithiones (211) at C-2 (Scheme 85) [80JCR(S)148],... 

Oxazines and 1,3-thiazines have been used quite extensively as substrates in pyrimidine syntheses (B-94MI 602-0l>. 1,3-Thiazines are intermediate structures in several cyclization reactions involving thioxo substrates. Pyrimidine formation from thiazines may involve a Dimroth-like rearrangement of a thiazinamine, an aminolytic displacement of the ring sulfur atom, or a combination of both. Aqueous ethanol in methylamine converts 4-phenyl-5-phenylsulfonyl-2//-l,3-thiazine-2,6(3//)-dithione (589) into the pyrimidine (590) by displacement of the ring sulfur and a nucleophilic substitution of the thioxo sulfur in the 2-position (Scheme 93) (88JHC835). 

When 5-cyano-4-methyl-l,3-thiazine-2,6-dithiones (68) react with methyl iodide, selective... 

The reactions of l,3-thiazine-2,6(3//)-dithiones (138) have been well studied (e.g., <84JHC953 . They combine with thiols in the presence of potassium hydroxide at 60°C to give the 2-thio-l,3-thiazine-6-thiones (139) and then, if there is an excess of the thiol, 2,2-dithio-2,3-dihydro-1,3-thiazdne-6-thiones (140) (Scheme 25). 

Thiadiazin-4-ones are obtained by heating dialkylaminocyanamides with COS under high pressure (see Section 6.18.10.2.2.iii), and the corresponding 4-thiones are formed by base-catalyzed ring-transformation of l,3-thiazine-2,6(3//)-dithiones in the presence of thiourea (see Section... 

CftHgN2S3, 2,4-Dimethyl-1,2,4-thiadiazolidine-3,5-dithione, 40B, 338 CftH6Nft03S2, 5-Acetamido-1,3,4-thiadiazole-2-sulphonamide, 40B, 338 Ci,H7N02S, (R)-Thiazolidene-4-carboxylic acid, 45B, 368 C5H5NO3S, 4-Hydroxymethylisothiazole-3-carboxylic acid, 44B, 353 C5H5N3OS, [1,2,4]Triazolo[3,2-b][1,3]thiazin-5-one, 46B, 390 C5H5N3OS2 f 2,3,6,7-Tetrahydro-4H-thiazolo[3,2-a]s-triazin-2-on-4-thione, 40B, 263... 

The interaction of l,2-dihydro-4//-benzo[with acid hydrazides provides very satisfactory yields of 5-substituted 3-(o-amino-phenyl)-l,3,4-thiadiazoles (94), undoubtedly by way of the intermediate iV-(2-aminothiobenzoyl)-N -acyl-hydrazines (93). ... 

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