Tertiary amides phosgene

Buijle et al. [19] reported that ynamines can be obtained by the dehydrohalo-genation of a,a-dihaloamides. The a,a-dihaloamides can be obtained by the reaction of phosgene with tertiary amides [20]. An example of the use of this... 

The reaction of tertiary amides with phosgene immonium chloride (51) allows this approach to be extended to the synthesis of thiomalonamides (52 equation 23). ... 

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. ... 

The Vilsmeier (or Vilsmeier-Haack or Vilsmeier-Haack-Arnold) reaction is primarily a mild method for formylating a wide variety of substrates.1 It has limited application to higher acylation and involves the reaction of a Vilsmeier reagent derived from a tertiary amide and an acid chloride (or occasionally a bromide). The most commonly employed amide is jV,N-dimethylformamide (DMF) and the acid chloride is generally phos-phoryl chloride, though phosgene and thionyl chloride are also employed. 

Trichloromethyl chloroformate (diphosgene) is used as a safe substitute for highly toxic phosgene gas. The latter is generated in situ by addition of catalytic amounts of tertiary amines or amides, or active carbon. Diphosgene also disproportionates to 2 equivalents of phosgene on heating above 250°C. 

Chloroformates, chlorocarbamates, and phosgene are similarly reactive toward organomagnesium compounds. The first two provide useful syntheses of esters and amides, respectively, but phosgene usually leads to the tertiary alcohol. 

Phosgene and tertiary carboxylic acid amides form very labile adducts (17 equation 6 not yet isolated or used for preparative purposes as such), which decompose with loss of CO2 very rapidly to give amide chlorides (see Section 2.7.2.2.1.i). Decomposition with evolution of CO2 is a common fate of primary adducts of carbonic acid chloride derivatives. Primary adducts from DMF and chloroformic acid esters (18), for example, decompose immediately to give alkoxymethyleneiminium chlorides, which react to give alkyl chlorides and DMF (equation 7). Adducts (19) from secondary and tertiary carboxamides... 

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