Triphosgene reaction with amides

Microwave irradiation can be used to make oxazolo[4,5-fc]pyridines and allows reaction with amides in lieu of acids when urea or thiomea are used, 2-ones (2-thiones) are obtained carbon disulfide with potassium hydroxide also leads to 2-thiones. The use of triphosgene and 2,3-diamino-pyridines can be used to made the analogous imidazo[4,5-b]pyridin-2-ones. Reaction with cyanogen bromide gives... 

Phosgene, as well as the easier to handle diphosgene (chloroformic acid trichloromethyl ester) or triphosgene (carbonic acid bis(trichloromethyl) ester) transform primary, secondary and tertiary amides and thioamides to chloromethyleneiminium chlorides (25 equation 15), whereby the reaction with thioamides is of broader scope and proceeds with fewer side reactions. The amide chlorides derived from primary and secondary amides can lose HCl, giving nitriles or imidoyl halides, respectively. /V-Sub-stituted formamides can be converted to isonitriles via amide halides. ... 

Chlorination of phosphines. Both trialkyl- and triarylphosphines afford the dichlorides on reaction with triphosgene, which can then be used to convert epoxides to 1,2-dichloroalkanes, aldehydes to gem-dichlorides, amides to nitriles, formamides to isonitriles, ureas to carbodiimides, and amines to triphenylphosphoranylimines. 

The synthesis was initiated from 45 by displacement of the primary tosyl group with either functionalised or nonfunctionalised primary or secondary amines in NMP at 80°C to give 46. After coupling of the primary amines, the resulting secondary amines 46 were converted into ureas 47 by reaction with isocyanates or by stepwise treatment with triphosgene followed by amine addition. In addition, acyl chlorides can be employed to provide amides as exemplified for 4 9 (Scheme 4.1.10). 

The following section highlights some selected recent applications of the use of phosgene equivalents in the preparation of Vilsmeier-type chlorinated derivatives of amides and ureas. Thionyl chloride, carbonyl bromides, phosphorus oxychloride, phosgene, triphosgene, oxalyl chloride, and p-toluenesulfonyl chloride are all efficient oxophilic promoters capable of generating Vilsmeier-type chloro imi-nium ion intermediate 1770 by reaction with formamides, particularly dimethyl-formaraide, and ureas. 

The amides 23, i.e., the products from the reaction of the anhydride (1) and the acetylenic amides 21 (see part 1), undergo cyclization to the derivatives of oxazoloquinazoline 275 (yields 31-50%) when treated with triphosgene in pyridine. The configuration of the initial amines 21 and amides 23 is retained [10],... 

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