Phenyl dichlorophosphate activator

It provides from good to excellent yields in oxidations performed from — 10°C to room temperature267 Briefly mentioned by Liu and Nyangulu2673 as a less satisfactory activator than phenyl dichlorophosphate... 

Nyangulu267a as a less satisfactory activator than phenyl dichlorophosphate... 

Table 2.2. lists activators used less commonly for Moffatt oxidations. The following activators, namely diphosgene,262 triphosgene,263 2-chloro-1,3-dimethylimidazolinium chloride,264 l-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluenesulfonate,265 triphenylphosphine dibromide and dichloride,266 and phenyl dichlorophosphate,267 have been the subject of scientific monographs, in which they are proposed as suitable and convenient alternatives to more routinely used activators, and can offer improved oxidation conditions in some substrates. 

Thiol esters can be prepared directly from carboxylic acids by reaction with thiols in the presence of phenyl dichlorophosphate as the activating agent (equation I).s... 

Esterification. Esters can be prepared in 70-95% yield by the reaction of an acid and an alcohol in the presence of pyridine (3 equiv.) and (CH3)2NPOCl2 (1.5 equiv.) at room temperature. Phenyl dichlorophosphate, C6H5OPOCI2 (1,847), can also be used as the activating agent, often with somewhat improved yields. However, this variation results in much lower yields in the case of penicillins. This esterification is applicable even to tertiary alcohols. 

A practical synthesis of a-amido 3-lactams uses a Dane salt (9) formed by the reaction of a methan-olic solution of the potassium salt of glycine with methyl acetoacetate (Scheme 9). The salt (9) readily reacts with a Schiff base in the presence of triethylamine and e.g. a chloroformate ester. Other activating agents such as phenyl dichlorophosphate - or phosphorus oxychloride - have also been successfully used. 

Esterification.—iVAWW -Tetramethylchloroformamidinium chloride, which is readily prepared from iVAWW -tetramethylurea and oxalyl chloride, is an efficient reagent for the esterification of carboxylic acids with alcohols yields of between 66 and 97% are obtained, and the method has also been applied to macrolide synthesis. A modified one-pot procedure for the esterification of carboxylic acids, using phenyl dichlorophosphate-dimethylformamide complex, has appeared. A simple method of activation of carboxylic acids, using methanesulphonyl chloride and triethylamine followed by addition of the alcohol and 4-dimethylaminopyridine, leads to esters in 57— 96% yield for thirteen examples. 0-Methylcaprolactim reacts with carboxylic acids to give methyl esters in 73—91 % yield for seven examples and 2-iodoethyl esters are prepared from acyl chlorides, ethylene oxide, and sodium iodide. Transesterification, catalysed by titanium(iv) alkoxides, provides an effective method for synthesis of esters. Diethyl trichloromethylphosphonate reacts with carboxylic acids to give ethyl esters via transesterification, in 52 to 98 % yield. ... 

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