Trifluoromethanesulfonic Anhydride reaction with amides

Primary and secondary amides and thioamides react with alkyl chlorofoimates with loss of CO2 or COS, forming iminium chlorides (82 equation 52). In some cases this method is complementary to the Pinner imido ester hydrochloride synthesis. The iminium salt (83 Scheme 6) formed by action of ethyl chloroformate on DMF is labile and decomposes rapidly to ethyl chloride. If the reaction is performed in the presence of NaBp4, the iminium salt (85) is isolable. Aryl chlorofoimates react in the same fashion with DMF or DMA, but in these cases the aryloxymethyleneiminium compounds are fairly stable, so this reaction is an important method for the preparation of compounds of this type. - Succinic acid monoamides, phthalic acid monoamides and related compounds are cyclized to iminium salts (86 equation 53) by treatment with acetic anhydride and HC104. ° With the aid of trifluoromethanesulfonic anhydride lactams and amides can be converted to dication ether salts (87) and (88 Scheme 7).22i.222... 

For reaction with azides, amides can be activated with trifluoromethanesulfonic anhydride or benzo-triazole, or via formation of the thioamide, or by the use of triphenylphosphine with diethyl azodicar-boxylate. Alternatively, imidochlorides can be used under phase-transfer conditions. ... 

Tetrazoles are usually prepared by the reaction of an azide with a nitrile, or an activated amide tri-n-butyltin azide and trimethylsilyl azide are more convenient and safer reagents than azide anion is some cases. The second example shown illustrates the use of a cyanoethyl group as a removable protecting group for amide nitrogen. Other variations on this method from nitriles include the use of triethylammonium chloride (instead of ammonium chloride) to avoid the possible sublimation of potentially explosive azides, and the use of micelles as reaction media. Amides can be activated with trifluoromethanesulfonic anhydride, or via formation of the thioamide, or by the use of triphenylphosphine with diethyl azodicarboxylate the equivalent imidochloride will react under phase transfer conditions. ... 

Keteniminium salts undergo [2-1-2] cycloaddition reactions with unreactive olefins, such as ethylene, cyclopentene, cyclohexene and styrol to give cyclobutane ammonium salts 23, which are readily hydrolyzed to give cyclobutanones 24. Likewise, reaction with acetylene derivatives affords cyclobutenylidene ammonium salts 25, which are also readily hydrolyzed to give the cyclobutenones 26. Some of the [2-1-2] cycloadducts obtained from keteniminium salts and olefines are shown in Table 4.17. The keteniminium salts are easily synthesized from suitable dimethylamides and phosgene, or trifluoromethanesulfonic acid anhydride. The reaction of the amide with phosgene generates a chloro compound 21, which is in equilibrium with the ketenimine salt 22. 

Amides of trifluoromethanesulfonic acid (triflamides) can be prepared by the reaction of the corresponding amines with triflic anhydride The most applicable in organic synthesis are iV-phenyltriflamides, which can be used as mild and selective Inflating reagents [110, lll ... 

The most important method for the preparation of aryl ketones is known as Friedel-Crafts acylation. The reaction is of wide scope. Reagents other than acyl halides can be used," including carboxylic acids," anhydrides, and ketenes. Oxalyl chloride has been used to give diaryl 1,2-diketones." Carboxylic esters usually give alkylation as the predominant product (see 11-11)." A-Carbamoyl p-lactams reacted with naphthalene in the presence of trifluoromethanesulfonic acid to give the keto-amide." ... 

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