Isocyanurates halides

Whilst reaction can take place in the absence of catalysts it is more common to use such materials as tetra-alkylammonium halides and tertiary amines such as triethylenediamine. A major side reaction leads to the production of isocyanurate rings, particularly in the presence of tertiary amines. 

The inherent problems of cotrimerization may be circumvented by using the reaction of inorganic cyanates with organic isocyanates to form the salt (158), which can react with an alkyl halide to give the isocyanurate (159 Scheme 96) (70JHC725). The reaction does give the symmetrical isocyanurate as a by-product but it is readily separated from the salt. The route can be applied to the synthesis of many isocyanurates. 

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