Reactions at an oxygen centre

Phosgene is reported to combine with a wide range of oxygenated materials, including alcohols, ethers, ketones, carboxylic acids, anhydrides, lactones, esters, carbonic acid derivatives, etc. Only the reactions of COCIF with alcohols, phenols and cyclic ethers have been reported, resulting usually in the generation of fluoroformates. Such materials can often be usefully converted into the corresponding fluoro compound by means of decarboxylation in the presence of BF3, EtjO, pyridine, or other materials. 

Ethanol combines with COCIF at low temperature to give predominantly ethyl fluoroformate some diethyl carbonate is also produced. No base catalyst is required for the reaction [589]  

The tertiary alcohol (16.4) reacts with COCIF in the presence of NEtg to give the corresponding fluoroformate [2121]. 

Reaction of a benzene solution of HOCH jCH jOH with COCIF in the presence of a tributylamine catalyst for 12 h at 20 C gave a yield of 99% FC(0)0CH CH jOC(0)F and 1% of ethylene carbonate [384,379]. Treatment of this bis(fluoroformate) with BFg.OEtj at 120 C gave 1,2-difluoroethane in a yield of 28.6% [379]. This reaction can be extended to include other polyhydric alcohols from which polyfluoroformates may be generated [384]  

Aliphatic or alicyclic fluoroformates may be prepared continuously from the reaction of the corresponding alcohols with a mixture of carbonyl halides e.g. COFj, COCIF and COClj at -20 to +80 C in the presence of isobutene, which acts as a hydrogen halide acceptor). The process was illustrated using methanol, t-butanol and cyclohexanol as examples [1118]. 

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