Triaryl cyanurates

Aromatic cyanates trimerize on heating in the presence of catalysts, thus forming triaryl cyanurates (Scheme 2)... 

Etherification. With the use of poly(ethylene glycol) [PEG] as a phase-transfer catalyst (PTC), diaryloxymethanes are readily prepared from ArOK and CHjCl in methanol at room temperature. The same catalyst is used in a synthesis of triaryl cyanurates from cyanuric chloride. 

Triazines with three different substituents are formed by variations on the above methods. There is no efficient route to trialkyl or triaryl derivatives, although the reaction of acylimidates and amidines has met with some success (see Section 2.20.4.6.2). In general the best routes available are as follows, (a) Substitution reactions of cyanuric chloride, (b) The condensation of Af-cyanoamidine with chloromethyliminium salts, (c) 2-Aryl-1,3,5-triazin-2-ones may be efficiently prepared by ring closure reactions on AT-(a-chloroalky-lidene)carbamoyl chloride and amidines (see Section 2.20.4.4.1). 

Depending on the substituents present in the aromatic nucleus, the cyanates show more or less tendency to trimerize in the presence of mineral acids, Lewis acids, bases, as well as phenolic impurities. The reaction proceeds quite smoothly and, therefore, the cyanates become a very useful starting point for the preparation of a large variety of triaryl esters of cyanuric acid. 

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