Trifluoromethanesulfonic acid enol triflates

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. ... 

Various pH aqueous solutions (pH = 1-6) of trifluoromethanesulfonic acid were prepared independently, and the model reaction of the silyl enol ether derived from cyclohexanone (2) with benzaldehyde was tested. Six independent experiments were performed (pH = 1, 2, 3, 4, 5, 6). In the pH 5 and 6 solutions, only a trace amount of the product was detected on TLC, the yields were less than 5%, and hydrolysis of 2 was also observed. In the pH 1-4 solutions, the silyl enol ether immediately hydrolyzed to give the original ketone, and no aldol adduct was obtained. From these experiments, the protons that may be produced from the hydrolysis of the lanthanide triflates were found not to be an active catalytic species in the present aldol reaction of silyl enol ethers with aldehydes the pH values of Yb(OTf)3 solutions were measured as 5.90(1.6x 10- M,THF-H20,4 l)and6.40(8.0x 10- M, HjO). 

The combination of a secondary benzyl alcohol with Hf(OTf)4 in nitromethane was a highly effective secondary benzylation system. Secondary benzylation of carbon (aromatic compounds, olefins, an enol acetate), nitrogen (amide derivatives), and oxygen (alcohols) nucleophiles was carried out with a secondary benzyl alcohol and 1 mol % of Hf(OTf)4 in the presence of water. Secondary benzyl alcohols and nucleophiles bearing acid-sensitive functional groups (e.g.,icri-butyldimethylsilyloxy and acetoxy groups and methyl/benzyl esters) could be used for alkylation. Hf(OTf)4 was the most active catalyst for this alkylation, and trifluoromethanesulfonic acid (triflic acid, HOTf) also proved to be a good catalyst. In such cases, the catal)fiic activity of metal triflates and HOTf increased in the order La(OTf)3 [Pg.346]

Facile synthesis of simple 3-arylpyrroles from pyrroline by tandem Suzuki dehydrogenation reaction is depicted in Scheme 229. Thus, treatment of l-benzyl-2,5-dihydro-l//-pyrrol-3-yl trifluoromethanesulfonate 1195 (prepared in 55% yield from l-benzyl-3-pyrrolidinone 1194 by trapping the enolate with a triflating reagent), with boronic acid derivatives leads to the formation of 3-arylpyrroles 1196 in good yields (65-74%) <2000TL3423>. 

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