Triazinium 2-dicyanomethylides

Triazinium 2-dicyanomethylides 4 were readily prepared by reaction of 1,2,3-triazines 1 with oxiranetetracarbonitrile (tetracyanoethylene oxide) in tetrahydrofuran at room temperature.47 228... 

Disubstituted-2-methyl-1,2,3-triazinium iodides 114a-c are demethylated to the triazines 17m,s,u by reaction with formamide and diammonium persulfate (Equation 92) < 1991H(32)2015>. This special case has already been mentioned in Section 9.01.5.6 together with the removal of 2-dicyanomethylene groups from the 1,2,3-triazinium dicyanomethylides 34 (R = H R, R = Me, Et, Ph) under the same conditions see also <1996CHEC-11(6)483>. Cycloadditions of 2-ethyl-1,2,3-triazinium tetrafluoroborates and 1,2,3-triazinium 2-dicyanomethylides have been treated in Section 9.01.5.7. 

Vicarious nucleophilic substitution of 1,2,3-triazinium 2-dicyanomethylides (75) with... 

The instability of the ring system has prompted the use of indirect methodology for substitution, and it was found that triazinium dicyanomethylides (79) are useful compounds for the introduction of substituents into the C-5 position (Scheme 11). Radical nucleophilic carbamoylation, which was developed by Minisci et al. <90JHC79>, was applied to triazinium dicyanomethylides to form... 

Triazinium dicyanomethylides 34a-d react with DMAD at 100°C in a 1,3-dipolar cycloaddition to yield the bicyclic adducts 153, which were isolated and completely characterized spectroscopically. They are stable under inert gas at 0°C, but in CDCI3 solution a slow rearrangement to 154 is observed which is sensitive to oxygen and eventually forms 156 upon workup (Equation 53) <2004EJO4234>. 

Triazines react with tetracyanoethylene oxide (TCNEO) to afford the stable triazinium 2-dicyanomethylides 84. 

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