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Pyrazoline-3-thiones, tautomerism

C NMR, 5, 193 Pyrazoline-5-thiones tautomerism, 5, 215 Pyrazoline-5-thiones, 1-aryl-reactions, 5, 102... [Pg.776]

When the oxygen atom is replaced by a sulfur atom as in pyrazoline-5-thiones, the CH form (145a) never occurs, and the tautomerism implies only the SH (145b) and the NH (145c) forms (77BSB949). [Pg.215]

More complex tautomeric equilibria have been observed for compound 21 involving the l,2,4,5-tetrazin-3-thione G. The equilibrium is strongly shifted toward the isoxazoline form A in solvents such as pyridine, acetone, dimethyl-sulfoxide (DMSO), and dimethylformamide (DMF), whereas the pyrazoline form D does not exceed 5-10% (Scheme 3) <2002CHE730>. The presence of the above tautomeric species has been demonstrated by NMR. 5-Hydroxy-3,3,5-trimethylisoxazolidine showed a similar behavior <2003CHE1257>. The presence of a CF3 group such as in 22 affects considerably the stmcture of these compounds, which exist only in the cyclic isoxazoline form <2000RCB1910>. [Pg.374]

See other pages where Pyrazoline-3-thiones, tautomerism is mentioned: [Pg.776]    [Pg.776]    [Pg.48]    [Pg.20]    [Pg.20]    [Pg.153]    [Pg.275]    [Pg.318]   
See also in sourсe #XX -- [ Pg.76 , Pg.256 ]

See also in sourсe #XX -- [ Pg.76 , Pg.256 ]



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