2- Substituted-5-phenyl-6//-1,3,4-thiadiazine

The 6- or 7-phenyl-substituted l-ethyl-pyrazino[2,3-r-][l,2,6]thiadiazine 2,2-dioxides 187 were found to show significant platelet aggregation inhibition comparable to other antithrombotic agents. Strong evidence was found that this activity was due to interference with the platelet arachidonic acid pathway <1999JME1698>. 

In El mass spectrometers, 1-phenyl-substituted 1,2,4-thiadiazine 1-oxides can undergo migration of the phenyl group from the sulfur atom to nitrogen, a common feature in the mass spectra of aryl alkyl sulfoximes (77JOC952). 

After several attempts to attain the pyridothiadiazine ring system, 2-chloro-3-hydrazinopyridine (322) was reacted with phenyl isothiocyanate in methanol to give the amino-substituted pyrido[3,2-e]-l,3,4-thiadiazine (323) (30%) <88M333>. 

In Table 36 are shown a series of substituted 3.4-dihydro-2H-1,3,4-thiadiazine-2-thiones prepared by Mathes (251). Since the cyclization reaction except in the instance of a-chloroacetyl acetate were carried out in acid medium, the question arises whether these products are really 3,4-dihydro-2H-l,3,4-thiadiazine-2-thiones. Since the 5-phenyl-... 

In the solid state, compounds (R = phenyl) are in their NH form (88JCR(S)94), which is the tautomer preferred in polar aprotic solvents (DMSO), except for compounds in which R = NHj, which always exist as the CH (B) tautomer (Section II,A,3,b). In nonpolar solvents (CDClj), mixtures of NH (A) and CH (B) tautomers are present. The value of depends on the nature of R. In basic solvents (pyridine), the common anionic form exists (Section II,B,l,a). The OH (C) tautomer, which exists in related pyrazoles in a high percentage (76AHC(Suppl)316), is not present in these thiadiazine derivatives. On the other hand, 6-substituted derivatives, which... 

The ease of polychlorination of l-chloro-3-phenyl-lA, 2,4-benzothiadiazine (93)- (94) at the carbocyclic ring rather than at the 3-phenyl substituent is indicative of the activating effect of a fused U, 2,4-thiadiazine ring on the benzene nucleus <89JOU550>, a result in direct contrast to the electrophilic substitution of U, 2,4-thiadiazine 1-oxides under strong acid conditions (see Section... 

Amino- or 2-alkylamino-5-phenyl-677-l,3,4-thiadiazines 73 react with methyl iodide to give 2-alkylimino-3-methyl-4-phenyl-2,3-dihydro-6/7-l,3,4-thiadiazines 74 (Equation 8) <2006UP1>. 3-Substituted-2-imino-5-methyl-... 

The thiadiazines 105, on boiling with aqueous ethanolic (1 1) sodium hydroxide solution, are found to isomerize into the corresponding l-phenyl-2-phenylamino-4-(substituted) benzylidene amino-6-thio-l,3,5-triazines, 107 (Scheme 14) <2005IJB638>. 

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