Ammonium trifluoroacetate catalyst

More recently, Angell et al. have used mixtures of ammonium salts with organic anions, such as EAN with ammonium trifluoroacetate, to produce electrolytes for fuel cells suitable for operation between 100 and 200 °C. An advantage of these electrolytes over aqueons ones is that they can be neutral, unlike aqueous electrolytes, which are either acidic or basic, and hence, there are more possible catalysts that can be used and cell designs can be simpler. 

Trisubstituted imidazoles have been synthesized from 1,2-diketones or a-hydroxyketones with ammonium acetate in very short reaction times with excellent yields in the presence of l,l,3,3-VAr V ,(V -tetramethylguanidinium trifluoroacetate as an ionic liquid <06SC65>. Iodine acted as an efficient catalyst in the synthesis of 1,2,4,5-tetraarylimidazoles 93 using benzoin 91,... 

Further variations of the basic motif of 1 comprise carbene le in which the anionic ligands are trifluoroacetate rather than chloride (Fig. 2) [4d]. However, this specific compound shows a significant tendency to isomerize the double bonds of the substrates in addition to its metathetic activity. Moreover, water soluble catalysts have been developed that contain bulky aliphatic phosphine ligands with either a quarternary ammonium group (lf,g) or a sulfonate function (lh) [12]. They have been tested in the ring opening polymerization... 

The reaction is acid or base catalyzed. Many catalysts have been tried, including potassium acetate and sodium acetate (27), dimeth-ylformamide (DMF) (28-30), urea ammonium sulfate (29), magnesium perchlorate (31-33), trifluoroacetic acid (32), boron trifluoride (30), sodium acetate (31), potassium hydrogen phosphate (34), and y-rays (35). The best acetylation condition, however, is uncatalyzed acetic anhydride in xylene at 100-130 C (36). 

Transient siloxanolate anionic catalysts prepared by reacting four moles of D-4 with one of tetramethyl ammonium hydroxide at 80 C are effective for equilibrating "neutral" systems such as the epoxy ( ), "basic" dimethyl-amino (64) or aminopropyl (59,67) end-blockers and D-4. With "acidic" functionality on the end-blocker, we have successfully utilized trifluoroacetic acid for the equilibrations. Further details of the oligomer synthesis and their utilization in segmented copol)nners will be described in future publications. 

The adduct resulting from this Ugi-Smiles coupling contains an N-aryl unit that offers great synthetic potential for further functionalization. Scheme 5.26 shows just one such an example. The reaction of 2-iodo-4-nitrophenol (90) with allylamine, 3-methylbutanal, and benzyl isocyanide in the presence of ammonium chloride afford the Ugi-Smiles adduct 91, which, without purification, underwent palladium-catalyzed Heck cydization to afford indole 92 in 72% yield. Trifluoroacetic add (O.lequiv.) was introduced before addition of the palladium catalyst in order to destroy any remaining isocyanide, which was harmful to the subsequent cydization due to catalyst poisoning [51]. 

Phenols (e.g., phenol itself [CeHs-OH or Ar-OH], Table 6.10, item 2) and their esters (e.g., the trifluoroacetate ester of phenol [C6H5-O2CCF3 or Ar02CCH3], Table 6.10, item 3) have been oxidized with air and oxygen (O2), in neutral and alkaUne solutions, with and without ionic and/or radical catalysts and/or irradiation and in a variety of solvents. Enzymes (this chapter and Chapter 12) from a wide variety of sources have also been used. Frequently, oxidation of aromatic systems to phenols cannot be stopped before quinones and products of ring fragmentation occur and numerous, sometimes ill-defined, products result. Thus, as shown in Equation 6.80, oxidation of the polynuclear hydrocarbon chrysene with anunonium cerium(IV) sulfate [ceric ammonium sulfate, Ce(NH,)4(S04)4] is reported to produce 6H-benzo[d]naphtho[l,2-/>]pyran-6-one (8% yield) and a quinone (23% yield). The remainder of the product(s) (69%) was unidentified. 

Other researchers [50] deal that the use acid-base catalyst (ammonium salts acetates and trifluoroacetates of diethylammonium, morpholinimn, piperidinimn) promotes the creation of the Knoevenagel-Cope condensation product (X,P-imsaturated nitrile) and enhances the yield of final 2-aminothiophene. Ionic liquids used as solvents in combination with ethylenediammonium diacetate were shown to be very efficient in the case of the Gewald synthesis with aliphatic and alicyclic ketones with possibility of regeneration of used liquids [83]. 

BINAP-ligated complexes 17-19, which are functionahzed with hydrophilic ammonium units, and successfully apphed them as catalyst for AH in aqueous phase. For instance, complex 17 enables the AH of ethyl acetoacetate in water, providing 100% conversion with 94% ee under relatively mild conditions (40 bar H2 at 50 °C for 16 h), and the catalyst could be recycled at least three times [79a]. In the AH of ethyl trifluoroacetoacetate, a challenging substrate, with Ru-BINAP or its derivatives, the complex 18 dehvered 95% conversion with 70% ee in an acidic aqueous medium (1.0m L water, 0.13 m L acetic acid, and 0.125 m L trifluoroacetic acid) [79c]. 

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