2.3.5.6- Tetrahydro-l,3-thiazin-4-one

Thioxo-3,4,5,6-tetrahydro-l,3-thiazin-4-ones (57) are A-acylated by acid chlorides in the presence of triethylamine to give 3-acyl-2-thioxo-3,4,5,6-tetrahydro-l,3-thiazin-4-ones (58) (Equation... 

Treatment of 1 l-methyl-2,3,4,6-tetrahydro[l, 3]thiazino[3,2-h]isoquino-lin-6-one (140 n = 0) and its 1,1-dioxide derivative (140 n = 2) with excess 30% hydrogen peroxide in 85% formic acid afforded 1,6-methanobenzo[g][l,5]thiazonine-7,12-dione (141) in 50 and 60% yield, respectively [80CPB1131, 80JAP(K)80/124767], No cyclization occurred when 9-(pent-4-enyl)-2,3,4,6,7,8-hexahydropyrido[2,l-b][l,3]thiazine and its 4-oxo derivative was treated with a Lewis acid [94H(37)441],... 

A soln. of 6-phenyl-2,3,4,7-tetrahydro-l,4,5-thiadiazepin-3-one 1,1-dioxide in acetic anhydride refluxed 6 hr. 4-(diacetylamino)-2,3-dihydro-5-phenyl-4H-l,4-thiazin-3-one 1,1-dioxide. Y 50%. I. Sataty, Tetrahedron 28, 2307 (1972). 

The one-step synthesis of further tri- and tetracyclic pteridine derivatives from 2-aminopyrazine 153 has also been described <2001JHC1173>. Cyclic analogues of A -[bis(methylthio)methylene]amino reagents such as 2-(methylthio)-2-thiazoline, 5,6-dihydro-2-(methylthio)-4//-l,3-thiazine, 2-(methylthio)-2-imidazoline, 2-(methylthio)-l,4,5,6-tetrahydro-pyrimidine, 2-(methylthio)-2-pyrazine, and 2-chloropyrimidine reacted with aminopyrazine 153 to afford thiazolo/thia-zino[2,3-3]- 159 ( = 1 (53%), n = 2 (42%)), imidazo/pyrimidino[2,l-/ ]- 160 ( = 1 (53%), = 2 (57%)), pyrazino[2,l-/ ]-161 (21%), and pyrimido[2,l-/ ]-pteridine 162 (42%) derivatives, respectively. 

The formation of thiazine systems by ring contractions of 2,3-dihydro-l,4-thiazepine 303 (Equation 108) <1971CC698>, 2,3>4,7-tetrahydro-l,4,5-thiadiazepin-3-one 3, 3 -dioxide 304 (Equation 109) <1972T2307>, 2,3-dihy-drobenzo[ ][l,4]thiazepin-4(57/)-ones 305 and 306 (Scheme 78) <1992LA403>, and 6,7-dihydro-1,4-thiazepin-5(477)-one. -oxide 307 (Equation 110) <1999H(51)1639> has been published. 

Treatment of 3,6-dihydroxy-3,4-dihydro-2//-pyrido[2,l-h][l,3] thiazinium salt (86) with orthophosphoric acid at 140°C for 34 h or with cone, sulfuric acid at ambient temperature for 5 h afforded 1 1 and 3 1 mixtures of pyrido[2,l-6][l,3]thiazine (87) and thiazolo[3,2-a]pyridine (88), respectively (70ACS2949). Under basic conditions, only extensive destruction of 86 was observed. When 3-hydroxy-2,3,4,6-tetrahydro[l,3]thiazino[2,3-a]isoquinolin-6-one was left to stand in cone, sulfuric acid at room temperature overnight, 4,6-dihydro[l,3]thiazino[2,3-a]isoquinolin-6-one was obtained in 61% yield (72ACS1620). 9-Oxido-3,4-dihydro-2H-pyrido[2,l-h] [l,3]thiazinium betaine did not undergo cycloaddition even under extreme conditions [81JCR(S)208],... 

The majority of syntheses of 1,4-thiazines involve the elimination of HL from species of type 11. Precursors of type 11a are not usually isolable compounds but are generated as intermediates. Two methods for the formation of such intermediates have been described one utilizes tetrahydro-1,4-thiazine-3,5-diones as starting materials, and the other requires diacyl sulfides and ammonia. Thus the synthesis of 2/f-l,4-thiazine (6), reported in 1948, was achieved by heating compound 16 at 450°C in the presence of powdered aluminum. Potentially, the procedure may be applied to the preparation of thiazines variously substituted at positions 2 and 6 however, the low yield (13%) achieved for the parent compound is a detraction. It was initially claimed that the reaction of diphenacyl sulfide with ammonia gave 3,5-diphenyl-4H-l,4-thiazine subsequent studies, however, revealed that the product was the 2//-tautomer 3,5-Diaryl-2/f-l,4-thiazines and... 

AP833>, and 3-acyl-3,4,5,6-tetrahydro-l,3-thiazine-2-thiones (59) are formed in the same way from the parent 3,4,5,6-tetrahydro-l,3-thiazine-2-thiones (60) (Equation (7)) <84AP74>. Both types of product are unstable and can be used as transacylating agents for amines and thiols. Thiocarbamoyl chlorides also react with 3,4,5,6-tetrahydro-l,3-thiazin-2-ones, but here both N- and (9-thio-carbamoylation can occur <86LA1140>. 

There have been reports of various 3-cyano-l-p-D-glucopyranosyl- and -1-P-D-galactopyranosyl-pyridin-2-ones and pyridin-2-thiones, along with o-l-arabinopyranosyl- and P-D-xylopyranosyl-3-cyano-2-pyridinethiones. 5-Amino-6-aryl-3-(P-D-gluco-or -galacto-pyranosyl)tetrahydro-2-thioxo-4H-1,3-thiazin-4-ones have been made by elaboration of the appropriate tetra-O-acetyl-P-D-hexopyranosyliso thiocyanates, and l-(2-acetamido-2-deoxy-P-D-glucopyra-... 

Several thioureas have been synthesized by ring-opening reactions of heterocyclic compounds such as l,3-dithiolan-2-thiones, 5-arylimino-l,2,4-dithiazolidine-3-thiones, benzoxazole-2-thiones, and 3,1-benzo-thiazine-4-thione derivatives. Similarly, the action of triphenylphosphine on 5-amino-l,2,4-dithiazolo-3-thiones gave thiocarbamoyl isothiocyanates (304). Other thioureas have been obtained by thermolytic decarbonylation of 2-amino-5(4H)-thiazolones and by treatment of 4,5,6,7-tetrahydro-cyclopenta-l,3-dioxin-4-one" and 3-nitrophthalic anhydride with thiourea. ... 

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