Phosgene phenol chloroformate

The course of the reaction of phosgene with alcohols and phenols is also interesting. With phenols it can react in two ways, according to the proportions of the two substances present. With one molecule of phenol and one of phosgene, phenyl chloroformate is formed ... 

Carbonates ate manufactured by essentially the same method as chloroformates except that more alcohol is required in addition to longer reaction times and higher temperatures. The products are neutralized, washed, and distilled. Corrosion-resistant equipment similar to that described for the manufacture of chloroformates is requited. Diaryl carbonates are prepared from phosgene and two equivalents of the sodium phenolates or with phenols and various... 

Alcohols and phenols can be attached to support-bound alcohol linkers as carbonates [467,665,666], although few examples of this have been reported. For the preparation of carbonates, the support-bound alcohol needs to be converted into a reactive carbonic acid derivative by reaction with phosgene or a synthetic equivalent thereof, e.g. disuccinimidyl carbonate [665], carbonyl diimidazole [157], or 4-nitrophenyl chloro-formate [467] (see Section 14.7). The best results are usually obtained with support-bound chloroformates. The resulting intermediate is then treated with an alcohol and a base (DIPEA, DMAP, or DBU), which furnishes the unsymmetrical carbonate. Carbonates are generally more resistant towards nucleophilic cleavage than esters, but are less stable than carbamates. Aryl carbonates are easily cleaved by nucleophiles and are therefore of limited utility as linkers for phenols. 

Phosgene reacts with alcohols or phenols (or their simple salt derivatives) to give two types of compound, chloroformates R0C(0)C1 Equation (4.7) and carbonates R0C(0)0R Equation (4.8), see Section 10.3.1. Carbonates are generally derived from the further reaction of the alcohol or phenol with the chloroformate. 

As with conventional phenols, silicon-substituted phenols are unreactive towards phosgene at room temperature [1408]. In the presence of NEt 3, HMe jSW-CjH OH and HMe2Si-4-CgH,OH were converted into the expected chloroformate derivatives. 

However, reaction of substituted silylated phenols with phosgene does not always give the chloroformate product, owing to the faster reaction represented below [1102] ... 

A number of developmental methodologies which are of interest in the herbicidal field have been examined for the formation of carbamates and related intermediates. Phosgene and phenol reacted in the presence of triphenylphosphine and a quaternary ammonium salt catalyst at 120-125°C over a total period of 10 hours gave phenyl chloroformate in 89% yield (ref.26). 

Phosgene reacts readily with aliphatic alcohols at room temperature or below to afford the corresponding aliphatic chloroformates in good yields, but phenols are much less reactive toward phosgene. Elevated temperatures (>100 °C) and scavengers or specifically designed catalysts (N,N -dimethylpropyleneurea, 2-undecylpyridine) are required to prepare aryl chloroformates [8, 9]. 

The same authors studied the synthesis of 2-alkoxy-5-n-propyl- or 2-alkoxy-5-sec-butylphenyl methylcarbamates as active intermediates for insecticides [218]. This involved phosgenation of the substituted phenol, followed by aminolysis of the formed chloroformate with monomethylamine. As already discussed, methylcarbamates can also be synthesized by reacting the appropriate phenol with methyl isocyanate. Thus, 2-isopropoxy-5-sec-butylphenyl chloroformate was synthesized by treating 2-isopropoxy-5-sec-butylphenol with phosgene. The product was reacted with monomethylamine to obtain the desired 2-isopropoxy-5-sec-butylphenyl methylcarbamate. Similarly, 2-sec-butoxy-5-sec-butylphenyl methylcarbamate, 2-iso-propoxy-5-n-propylphenyl methylcarbamate, and 2-sec-butoxy-5-n-propylphenyl methylcarbamate were also synthesized. 

The synthesis proceeds in two steps phosgenation of BPA forming oligomeric carbonates with phenolic and chloroformate end groups and polycondensation of the oligomers (see Scheme 3.8). For the phosgenation, BPA is first dissolved in an... 

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