Imidoyl chlorides reaction with, phosgene

The N-monosubstituted carboxamides, on reaction with phosgene, form imidoyl chlorides [2083a] ... 

This cyclization of a 2-(methylthio)anilide was discovered when an attempt was being made to prepare imidoyl chlorides by reaction with phosgene. 

Cyclic derivatives have also been prepared from quinoxaline-2,3-dithiones by reaction with phosgene (COClj), thiophosgene (CSCI2), and thionyl chloride (SOCI2). 2,3-Disubstituted quinoxalines result from the reaction of the dithiones with isocyanates, isothiocyanates, and imidoyl chlorides (e.g., PhCCl=NMe). Derivatives of quinoxaline-2,3-dithiones incorporating arsenic, antimony, and tin have been prepared for example, with BujSnCl the 2,3-disubstituted quinoxaline 22 is obtained, and... 

A practically useful method for synthesis of selenoesters has been developed by Barton et al. A wide range of aliphatic and aromatic selenoesters have been synthesized from the appropriate N -disuh-stituted imidoyl chlorides (58) using sodium hydrogen selenide to introduce seleniumJ Imidoyl chlorides (58) can be obtained by the reaction of amides with phosgene. Representative results are shown in Scheme 17 (formulae 59-61). 

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. ... 

Nitriles react with phosgene only in the presence of hydrogen chloride, to give either 1,2-unsaturated isocyanates or N-heterocyclic derivatives. The reactions are really those between COClj and the imidoyl chlorides or 1-chloroenamines, since these are the materials formed, reversibly, as equilibrium mixtures when hydrogen chloride adds to nitriles [2229] ... 

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 ( ). 

In the reaction of caprolactam with phosgene, the corresponding seven-membered ring imidoyl chloride LXIV is a logical intermediate. However, the product of reaction with a second mole of phosgene, 1-chlorocarbonyl-2-chloro-4,5,6,7-tetrahydro-lH-azepine (LXV), has only been isolated ( ). The mechanism of this reaction is discussed in detail in Chapter 3. 

The two reactive chlorine atoms at the opposite ends of the phosgene molecule determine the use of phosgene for addition reactions, polymerization reactions and for chain-enlargements. Other uses of phosgene are reactions with secondary amines to give imidoyl chlorides, with tertiary amines to form cationic complexes, with nitriles to produce heterocycles and with metal oxides to produce metal chlorides. 

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