1.2.4- Triazines, dihydro spectra

Base-catalyzed additions of HCN to s-triazine (1) give 2-cyano-l,2-dihydro-s-triazine (9). Its H-NMR spectrum shows that the hydrogen on the nitrogen is equilibrating rapidly between the 1- and 3- positions. When 9 is heated to 65°C it melts and eliminates HCN (72UP1). 

Atkinson and Cossey148 reported that the reduction of 2-methyl-5,6-diphenyltriazinium iodide (141) with potassium borohydride in methanol led to a tetrahydro-2-methyl-5,6-diphenyl-l,2,4-triazine. The ultraviolet absorption spectrum of this tetrahydro-l,2,4-triazine showed a maximum at 297 mfi (loge = 4.06). A similar reduction of l-methyl-3,5,6-triphenyl-l,2,4-triazinium iodide (142) gave a dihydro-1,2,4-triazine, the ultraviolet spectrum of which had maxima at 273 mft (loge = 4.46) and 410-420 m/x (loge = 3.62). No assignment of... 

Triazine (1) is highly 7c-electron deficient and readily attacked by nucleophiles. The parent triazine (la) slowly decomposed in methanol at room temperature, which suggested that nucleophilic attack of methanol occurred in the solution. The NMR spectrum of (la) in CD3OD measured at — 50°C in the presence of a base indicated that attack of methoxide ion on the 4-position was succeeded by ring-opening accompanied by the elimination of nitrogen (Equation (14)) <92H(33)63l >. All attempts failed to oxidize the intermediate 1,4-dihydro adducts to form 4-substituted triazines. 

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