Elimination trifluoromethanesulfonic anhydride

The total synthesis of mniopetal E (5) was achieved in a six-step sequence from the cycloadduct 125 (Scheme 21). The treatment of 125 with trifluoromethanesulfonic anhydride (Tf20) afforded triflate 129. Elimination of trifluoromethanesulfonic acid to introduce a double bond was accomplished in 2,6-lutidine at 100 °C, giving 130 in 84% yield. Deprotection of TBDPS ether was followed by Parikh-Doering oxidation of the resulting 131 by the same procedure used in the case of 127. Taking advantage of the electron-rich double bond between C-l... 

Electrocyclization is the key step in a route to 4//-imidazoles 1187 and imidazoles 1188. Thus, activation of AT-acylamidines 1183 with trifluoromethanesulfonic anhydride and subsequent condensation with amino compounds 1185 produces l-amino-2,4-diazapenta-l,3-dienes 1186. Deprotonation of 1186 by the use of strong organic bases yields the corresponding 4//-imidazoles 1187 or imidazoles 1188 after amine elimination through an anionic 1,5-electrocyclization reaction. For the cyclization to occur, the amino compound 1185 needs to possess electron-withdrawing substituents such as alkoxycarbonyl or fluorenyl groups (Scheme 290) <2004EJO2567>. 

An improved and convenient preparation of pyrimidines and condensed pyrimidines from ketones and nitriles was reported. In the presence of acetonitrile, the cation generated from methyl ethyl ketone with trifluoromethanesulfonic anhydride is trapped by the nucleophile, whereby a resonance-stabilized nitrilium species is formed. A second molecule of nitrile reacts with nitrilium intermediate, and after elimination of triflic acid, cyclization, and loss of a proton, the pyrimidine product was obtained in a useful yield. The formation of pyrimidines is accompanied by a minimum... 

A soln. of benzyl alcohol in methylene chloride added to a mixture of trifluoromethanesulfonic anhydride and 2 eqs. acetonitrile in the same solvent at room temp., and after 5 h hydrolysed with satd. NaHCOq soln. - N-benzylacetamide. Y 87%. The method is complementary to the standard procedure in coned. H2SO4 which is only applicable to tert. alcohols here, yields are optimum with prim, and sec. alcohols, whereas tert. alcohols undergo competitive elimination. F.e.s. A.G. Martinez et al.. Tetrahedron Letters 30, 581-2 (1989). 

Conversion of alcohols to sulfonate esters is a way of labilising them to nucleophilic substitution and elimination. The common leaving groups are arenesulfonates, particularly p-toluenesulfonate (tosylate), methanesulfonates (mesylate) and trifluromethanesulfonate (triflate) they are introduced by reaction of the acid chlorides (or, in the case of the trifluoromethanesulfonates, acid anhydrides) in a basic solvent such as pyridine. Traditionally, the reactions are carried out in pyridine as solvent, but both this solvent and the liberated... 

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. ... 

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