- 1,3-Oxazines and Related Compounds. VI. Synthesis and Some Reactions of 2,6-Disubstituted 4H-1,3-Thiazin-4-ones
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Various of 2,6-disubstituted 4H-1,3-thizin-4-ones (5) were synthesized by successive treatment of N-acylacetylcarboxamides with acid (such as 70percent perchloric acid or fluorosulfonic acid) and hydrogen sulfide.Reactions of 5 were investigated; ammonolysis with ethanolic ammonia gave the corresponding pyrimidin-4-ones; hydrolysis of 2-alkyl-1,3-thiazine derivatives yielded ring-opend N-acyl-β-mercaptocrotonamides; reduction with NaBH4 or LiALH4 afforded 3,4-dihydro-2H-1,3-thiazin-4-one derivatives.Keywords - 1,3-thiazin-4-one; 3,4-dihydro-2H-1,3-thiazin-4-one; pyrimidin-4-one; 1,3-oxazinium salt; 1,3-thiazinium salt; N-acylacetylcarboxamide; N-acyl-β-mercaptocrotonamide
- Yamamoto, Yutaka,Ohnishi, Shuhei,Azuma, Yutaka
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p. 1929 - 1935
(2007/10/02)
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- A NEW SYNTHESIS OF 1,3-THIAZIN-4-ONES VIA 1,3-OXAZINIUM SALTS FROM N-ACETOACETYLCARBOXAMIDES.
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In the formation of 1,3-oxazinium salts from N-acetoacetylcarboxamides (1), the effect of acids such as 70percent perchloric acid (3a), 98percent sulfuric acid (3b), 36percent hydrochloric acid (3c), saturated hydrogen chloride-ethanol solution (3d), trifluoroacetic acid (3e), and acetic acid (3f) was examined by the established method leading to the pyrazole (5) via 1,3-oxazinium salt (2), and the order was as follows; 3a > 3b > 3e 3d >3c (3f was uneffective).The result was applied to synthesize 2-substituted 1,3-thiazine derivatives (7a-e, 8a,b) via 1,3 oxazinium salts from 1a-f and hydrogen sulfide in the presence of acetic anhydride in satisfactory yields.
- Yamamoto, Yutaka,Azuma, Yutaka,Ohnishi, Shuhei
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p. 851 - 856
(2007/10/02)
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