Aryl ketones trifluoromethanesulfonic anhydride

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." ... 

The trifluoromethanesulfonic carboxylic anhydrides are highly effective acylation agents, which react without catalysts even with deactivated aromatics to yield aryl ketones (eq 26). ... 

One-carbon Homologation of Carboxylic Acids. l-[(Tri-methylsilyl)methyl]benzotriazole converts benzoyl chlorides to the corresponding (benzotriazol-l-yl)methyl aryl ketones in high yields (see eq 1). Treatment with triflic anhydride and 2,6-lutidine in CH2CI2 converts these ketones into their enolate triflates in 83-95% yields (eq 4). In the subsequent steps, the triflates are treated with sodium methoxide and then with ethanolic HCl to afford ethyl esters of the corresponding arylacetic acids in 89-98% yields (eq 5). The proposed reaction mechanism involves elimination of trifluoromethanesulfonic acid with sodium methoxide and final alcoholysis of the obtained l-(arylethynyl)benzotriazole intermediates with ethanolic HCl. A comparable classical method for one-carbon homologation of carboxylic acids, the Amdt-Eistert reaction, involves difficult to handle diazomethane and Q -diazoketones. ... 

An alternative approach to benzo[Z ]thiophene derivatives includes treatment of an aryl-substituted ketene dithioacetal monoxide 188 with trifluoromethanesulfonic anhydride [99] (TfjO) in the presence of K2CO3 in toluene at 25 °C, followed by addition of ethanolamine to the reaction mixture, provided benzo[fc]thiophenes, including 3-trifluoromethylbenzo[Z ]thiophene 189, in good yields. The cyclization proceeded through formation of reactive sulfonium electrophile [1(X)]. The synthesis of the starting material 188 was also facile and scalable, starting from aryl ketone 186 and formaldehyde dimethyl dithioacetal S-oxide (FAMSO) [101]. 

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See also in sourсe #XX -- [ ]

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