Thiazolo triazine-3,6-diones

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). 

Thiazolotriazines 636 (R = CO,Me) were prepared [84JCS(P1)2707] by cycloaddition of dimethyl acetylenedicarboxylate with triazine derivative 632. Derivatives of thiazolo[3,2-b][l,2,4]triazin-3,7-diones 637 have been formed (74JPR163) on reaction with aromatic aldehydes and diazonium salts to give 636 (R = Ar) and 638, respectively. Regioselective catalyzed... 

Cyclization of imidazo[4,5-e][l, 2,4]triazine 766 with bromoacetic acid and aromatic aldehydes gave (80URP765270) octahydroimidazo[4,5-e]-thiazolo[3,2-6][l,2,4]triazin-3,7-diones 767. 

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). 

With DM AD, the 3-thioxo-l,2,4-triazin-5-ones (269) formed thiazolo[3,2-i][l,2,4]triazine-3,7-diones (270) (Equation (31)) <84JCS(Pl)2707>. 

Thiazolo[3,2-6][l,2,4]triazines [CsNS-CsNs].— Investigations into the reactivity of 6-substituted 2,3-dihydro-7 -thiazolo[3,2-A][l,2,4]triazine-3,7-diones (78) have shown that, whilst condensation with aromatic aldehydes gives the 2-arylidene derivatives, the reaction with primary aromatic amines yields the corresponding 2,5-dihydro-3-arylamino[l,2,4]triazin-5-one, and not the expected anilides. ... 

Meso-ionic Thiazolo[3,2-a]-sym-triazine-5,7-diones. 2-Alkylaminothiazoles... 

---