Transition metal trifluoroacetates

The imine 217, formed from acetophenone and the 1-aminoimidazole, has been transformed into the enamine 218 which is then cyclized to 219 in trifluoroacetic acid (TFA) (Equation 40) <1995SC3271 >. The diaminoimidazole 220 reacts with ynone 221 to form 222 (Equation 41) <1998CHE1189>. Bromochalcones and chalcone dibromides can also be used in place of the ynone. Similar reactions have been used to prepare the dihydro analogues of 222 <1999CHE1207>. The reaction between 1-aminoimidazoles and 1,3-diketones has been extended to prepare bis-heterocyclic compounds, for example, 223 as ligands for transition metals (Equation 42) <2005EJI4382>. 

Silver ions (as silver trifluoroacetate or trifluoromethanesulfonate), Cu", and other transition metal ions in their 1h- oxidation state [99,100] are frequently employed to obtain [M-rmetal] ions from non-functionalized or at least nonpolar hydrocarbons, [101] polyethylene, [102,103] or polystyrene (for an example see Chap. 10.5.1). [99,100,104-106]... 

Indeed, it is not necessary for the central atom of the oxyanion to be a transition metal another atom with two different oxidation states is also effective. Recently, it has been found that, in trifluoroacetic acid solution, periodic acid oxidizes alkanes to low carbon number carboxylic acids (55). 

Figure 12. Supramolecular porphyrins obtained by coordination of transition metal complexes to the periphery of the macrocyclic ring (a similar scheme can be extended to the 3-TPyP and analogous porphyrazine species), [dmso = dimethyl sulfoxide (ligand), form = A,A-9-di- -tolyformamidinate, and TFA = trifluoroacetate.l...

Compound [Cr(C0)g(02CCF3)] may be prepared by oxidative substitution of Ag(02CCF3) or Hg(02CCF3)2 on [Cr2(CO)io] (218). Transition metal hydrido complexes have been obtained by oxidative addition reactions of trifluoroacetic acid which often lead to the formation of trifluoroacetato complexes. Equation (3) is an example of such a... 

Trifluoroacetato complexes of transition metals have also been obtained from oxidative elimination reactions in which neutral tt-acceptor ligands have been displaced in reactions with trifluoroacetic acid. These reactions may lead to hydrido complexes [Eqs. (6) (253) and (7) (26)] or they may not [Eqs. (8) (39) and (9) (19)]. 

A transition metal-mediated approach to amidation of glycal substrates can lead to the formation of 2-deoxy-2-trifluoroacetyl-amido derivatives. Thus, when a solution of (saltmen)Mn(N) is added to a mixture of trifluoroacetic anhydride (TFAA) and glycal 107 followed by sequential treatment with thiophenol and BF3 Et20, the 2-A-trifluoroacetamido thioglycoside 108 can be obtained in good yield and excellent diastereoselectivity (O Scheme 53) [91]. 

Direct C-H activation of hydrocarbon by means of transition metals has also been explored. Cyclohexane reacted with Pd(OAc)2 in the presence of potassium persulfate-trifluoroacetic acid under CO pressure and produced the desired cyclo-hexanecarboxylic acid in low yields and TON (eq. (13)). The electrophilic carbox-ylation is explained by the change of Pd(OAc)2 to Pd(OCOCp3)2 in trifluoroacetic acid as solvent. Electrophilic attack on a C-H bond should give an alkyl Pd complex. CO insertion followed by reductive elimination affords a reactive mixed anhydride which was detected before workup. 

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