1.3.5- Triazine formate equivalent

There are a considerable number of such syntheses in the literature. Most of the syntheses are based on the reaction of two equivalents of isocyanate with a nitrogen heterocycle. The two examples given are typical of the route (equation 103 and Scheme 107). The mechanism of formation of the l,3,4-oxadiazolo[3,2-a][l,3,5]triazine-5,7-diones (175) is included as it is of interest (74T221, 74JCS(P1)1786). 

The susceptibility of 1,3,5-triazine to nucleophilic attack with ring opening makes it a synthetically useful equivalent of formate, or formamide, particularly for the synthesis of other heterocycles, such as imidazoles and triazoles (see above). Despite the high susceptibility of 1,2,4-triazines to nucleophilic addition, 3-substituted-6-methoxy-l,2,4-triazines can be successfully lithiated. ... 

Shaw has described the oxidation of triazines with peracetic acid (very poor to high yields) and the preparation of 2,6-diamino-4-methyl-l,3,5-triazine A-oxides from potassium dicyanoacetamide and hydroxylamine (24-69% yield) <62JOC3890>. Kaugars and Watt reported the formation of triazine A-oxides from two equivalents of an amidoxime with ethyl orthoacetate, but only in low to moderate yields (13-48%) (see Section 6.12.9.2.2). 

The formation of a pyrimidine ring via an inverse-electron-demand Diels-Alder reaction turned out to be the key step in the total synthesis of (—)-pyrimidoblamic acid (40) reported by Duerfeldt and Boger in 2014 (Scheme 27) (14JA2119). Pyrimidine 41 was prepared via reaction of 1,2,3-triazine 42 (2.0 equivalents) with amidine 43 (1.0 equivalent) in anhydrous acetonitrile.The reaction mixture was first stirred for 14 h at 5 °C then another 6 h at 25 °C, furnishing the desired pyrimidine, 41, as a single diastereomer.With this intermediate, the authors were able to introduce the required stereochemistry for the desired product in one step. 

Another special feature connected with the 1,3,5-triazine moiety is spontaneous formation of a long-lived glassy state, by bisarylamino-1,3,5-triazines. A wide series of differently substituted derivatives 49 was synthesized by nucleophilic substitution of chlorine atoms in cyanuric chloride 20 with methylamine in the first step and then two equivalents of substituted aniline in the second step (13NJC3881). 

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