1.3.5- Triazines cyanic acid esters

Phosphorus pentachloride Trisaryloxy-l,3,5-triazines from cyanic acid esters... 

Figure 11 Thermal cyclotrimerization of cyanic acid phenyl ester 83 yielding 2,4, 6-triphenoxy-l,3,5-triazine 84 and chemical formulae of commercial cyanate esters 85-89 used as base resins to produce heat-resistant adhesives and moulding materials.

Aryl cyanates (cyanic esters), which can be prepared in situ (67AG(E)206), form 1,3,5-triazines under either acid or base catalysis (Scheme 83) (77RCR278, 78RCR975). The acid-catalyzed reactions are not properly understood, but it seems that the mechanism is dependent on the precise nature of the Lewis acid used. Yields are usually good (Table 14). The reaction of aryl cyanates with ketoximines yields 1,3,5-triazines (146) via the intermediate (145) (Scheme 84) (66CB2361). Alkyl cyanates are very reactive, and isomerize readily therefore they are unsuitable starting materials for 1,3,5-triazine synthesis. 

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