1.2.3.6- Tetrahydro-1,2,4-triazine 4-oxides ring-chain tautomerism

Ring-chain tautomerism was observed in a series of l,2,3,6-tetrahydro-l,2, 4-triazine 4-oxides 5 in nonpolar solvents (e.g., CCI4) by NMR spectroscopy. Depending on the nature of substituents R and R, the ratios of the cyclic form of 1,2,4-triazine 5a to the open-chain form of hydrazone 5b were found to be up to 45 55 (77ZOR2617). 

The tetrahydro-l,2,4-triazine 4-oxides (49a) in tetrachloromethane exist in equilibrium with the open-chain structures (49b) (77ZOR2617), and equilibria between triazinones (50a) and the open-chain form (50b) were also observed (80ZOR2297). Ring-chain tautomerism was also found with the aldehydes (51a 51b) here the triazine ring is present throughout (77CB1492). 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

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