Thiazolo -s-triazines

Formamidinoyl isothiocyanates (157) combine with 2-aminothiazoles the ring nitrogen attacks the spC part of the electrophilic reagent (312) further reaction then yields aza-condensed thiazolo-s-triazines (158) (Scheme 99) (313). Mesoionic S-alkvlthiazolo[3.2-fl]-i-tria2ine-5,7-diones (159) are obtained when 2-alkylaminothiazoles react with phenoxycar-bonyl isocyanate (304). 

Novel three-component reactions of thiazole Schiff bases, ammonium acetate and aromatic aldehydes under solvent-free microwave irradiation conditions yielded diastereoselectively thiazolo-s-triazines <06GC455>. 

Scheme 11.24. One-pot synthesis of pyrimidine systems [75, 76], thiazolo-s-triazine C-nucleosides [77], and 1,3-azaphospholes [78].

Yadav et al. reported a three-component coupling reaction under MW conditions for construction of a triazine system containing a thiazole core [85], In this reaction, a thiazole Schiff s base, an aldehyde, and NH4OAC react to yield thiazolo-s-triazine C-nucleosides 44 (Scheme 17.33). 

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... 

Tetrahydro-2H-thiazolo[3,2-a]-s-triazin-4-ones from 2,4-diaza-l,3-diene groups and isocyanates... 

Phenyl isocyanate added at room temp, to N,N-dimethyl-N -( 2 thiazolin-2-yl)-formamidine in benzene, and the product isolated after 10 min. -> 2-dimethyl-amino-3-phenyl-3,4,6,7-tetrahydro-2H-thiazolo[3,2-a]-s-triazin-4-one. Y 91%. F. e. and products s. R. Richter and H. Ulrich, B. 103, 3525 (1970). 

Dihydro-2iT-thiazolo[2,3-c][l,2,4]triazine-3,4-dione rearranges in dilute base to give an unstable acid which decarboxylates on acidification of the sodium salt to give 5,6-dihydrothiazolo[2,3-c]-s-triazole (equation 68) (81CB1200). Kinetic evidence has been put forward in favor of covalently hydrated intermediates in the acid-catalyzed rearrangement of triazolo[4,3-a]pyrazines to 1H-imidazo[2,1 -c]-s-triazoles. The intermediate triazole has been isolated and characterized (equation 69) (72JCS(P2)4). 

Synthesis of thiazolo[3, 272,3]ll,2,4]triazino[5,6-i)]indoles has been reported <04IJC(B)1585>. Different functionalizations of l,2,4-triazino[5,6-f>]indoles have been carried out <04JCR(S)183>. Reaction of 3-diazopyrazolo[3,4-clpyridazine with reactive methylene compounds yielded condensed 1,2,4-triazine derivatives <04H1143>. 

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