Phosphorus halides reaction with, phosgene

Most of the conventional reagents for the synthesis of acid chlorides from carboxylic acids are unsatisfactory for the preparation of a-keto acid chlorides. For example, the reaction of pyruvic acid with phosphorus halides does not give pyruvoyl chloride whereas the use of phosgene or oxalyl chloride affords ether solutions of the acid chloride in low yield. Recently a useful preparation of pyruvoyl chloride from trimeth-ylsilyl pyruvate and oxalyl chloride has been described."... 

Haszeldine and Iserson have also speculated [899,903] that various tetrahalomethanes can be prepared from the reactions of COBrF with phosphorus(V) halides, analogous to the reaction of phosgene with PClj to give CCl and POCI3. For example ... 

By analogy with the general synthesis of imidoyl chlorides it can be expected that carbamates and thiocarbamates undergo reaction with a variety of acid halides to afford 1-haloformimidates and 1-halothio-formimidates, respectively. For example, carbamates have been reacted with carbonyl chloride ( ), pyrocatecholphosphorus trichloride ( ), and phosphorus pentachloride ( ), and isocyanates were obtained. In view of the catalytic effect of N,N-dimethylformamide in the phosgenation of carbamates to isocyanates, the intermediacy of 1-chloroformimidates X is anticipated ( ). 

Acetylthio-l,2-dithioIylium salts have been described.116 A variety of methods are available for the preparation of 3-halides. The reaction of oxalyl chloride with l,2-dithiol-3-ones gives 3-chloro-l,2-dithiolylium salts (66)116 (Scheme 6). In some cases the reaction can be realized with 1,2-dithiole-3-thiones too. Phosgene can be used instead of oxalyl chloride. Oxalyl bromide gives the corresponding 3-bromo-l,2-dithiolylium salts.117 3-Chloro-l,2-dithiolylium dichlorophosphates have been prepared from 1,2-dithiol-3-ones and phosphorus oxychloride.118 The corresponding... 

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