1,2,4-Triazines Chichibabin amination reaction

Table 12 Yields of 3-amino-1,2,4-triazine 4-oxides derived from the Chichibabin amination reaction at room temperature ...

Diphenyl-l,3,5-triazine undergoes a Chichibabin-type amination reaction, the first example of this reaction to be reported for the 1,3,5-triazines. The 2-methylthio derivative (37 X = MeS) reacts exclusively via an Sn(ANRORC) mechanism rather than the SNAE mechanism (Scheme 21) (76RTC113). 

Reaction of nucleophiles with 1,3,5-triazines usually results in ring cleavage. Substitution reactions of the parent system (271) have been limited to the Chichibabin amination, which provides 272, and the preparation of alkyltriazines 273 via an Sn (ANRORC) alkylation (84M16). 

The amination of 2.4-diphenyl-1,3,5-triazine (7, X = H) with potassium amide in anhydrous liquid ammonia at -33°C occurs by a Chichibabin-type reaction, i.e. replacement of H" by NH via nucleophilic substitution involving an addition-elimination process (SsAE). In contrast, the 2-methylsulfanyl derivative 7 (X = SMe) is aminated nearly exclusively by a ringopening-ring-closing sequence [Sn(ANRORC)].52... 

A new version of the Chichibabin amination of azaaromatics in liquid ammonia in the presence of potassium permanganate, suggested by H. C. van der Plas, has been applied successfully in the series of 1,2,4-triazines (Scheme 65) <19858884, 2001H(55)127, 2004808(17)357>. The low-temperature amination reaction always takes place at the position 5, even in those cases where the 1,2,4-triazine ring bears a good leaving group at position 3. 

Simig, G., Van der Plas, H. C. The SN(ANRORC) mechanism. XVII. An SN(ANRORC) mechanism in the amination of phenyl-1,3,5-triazine with potassium amide in liquid ammonia. A novel mechanism for the Chichibabin reaction. Red. Trav. Chim. Pays-Bas 1976, 95,125-126. 

The examples shown are illustrative of the many easy nucleophilic additions to the polyaza-azines both 3-phenyl-l,2,4,5-tetrazine and 1,3,5-triazine itself add ammonia and simple amines (contrast the requirement for hot sodamide (Chichibabin reaction) for pyridine (8.3.1.2)) and thus amino and alkyamino derivatives can be obtained via oxidative trapping with permanganate. 

When 2-phenyl-l,3,5-triazine (8) is aminated with potassium amide in liquid ammonia at - 33 C a very slow Chichibabin reaction occurs, partly via the Sn(ANRORC) mechanism and partly via the SNAE process (ratio ca. 55 45). H NMR and l5N-labelling studies have demonstrated that in solution an equilibrium exists between the starting triazine, amine adducts, open-chain amidines and triazine product 9.53... 

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