Halides, cyanogen, with phenols

Aryl cyanates585 can be prepared by reaction of phenols with cyanogen halides in the presence of a base ArO + C1CN — ArOCN + Cl. 586 This reaction has also been applied to certain alkyl cyanates.587... 

Although isocyanates have been known for some time, the isomeric cy-anates were unknown until 1964. The latter were first prepared almost simultaneously by two different methods (1) thermolysis of 5-aryl- or 5-alkyloxy-l,2,3,4-thiatriazoles67 and (2) by reaction of phenols or alcohols with cyanogen halides.8 Since their synthesis, cyanates have ac-... 

Cyanate esters (CEs) are formed in excellent yields by the reaction of the corresponding phenols with cyanogen halide [34]. The reaction scheme is shown in Scheme la. The reaction is usually carried out in solution, in the presence of a tertiary amine as the acid scavenger at very low temperatures. Since the trimer-ization reactions of cyanate esters are highly prone to catalysis by spurious impurities, the most difficult aspect of cyanate ester synthesis is their scrupulous purification. Low molar mass esters are purified by distillation or recrystallization. Polymeric cyanates are purified by repeated precipitation in non-solvents such as water, isopropanol, etc. While distillation and recrystallization lead to pure materials, the precipitation method for polymeric cyanates is not always conducive to obtaining pure materials. A recent patent application claims a purification method for polymeric cyanates based on treatment with cation and anion exchangers [35]. 

In the early 1960 s Grigat (1) and Martin (2) and Jenson (3) reported the synthesis of stable aryl cyanates. Grigat (1) prepared these new materials by reacting phenolic compounds with a cyanogen halide. 

Up until 1960, the true cyanates, ROCN, had not been isolated. Thus, the reaction of sodium phenolates with cyanogen halides was shown to follow the course given in Eqs.(9) and (10) by both Nef, and Hantzsch and Mai. 

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