Trifluoroacetic acid-catalyzed cleavage

The participation of an urea group in the acid-catalyzed cleavage of a cyclopropane bond, which is one of the key steps in the synthesis of aza- and oxa-eburnamonine, has been reported.(2-Cyclopropylphenyl)benzylsulfone (13) was observed to give l-(2-benzylsulfonyl-phenyl)propyl trifluoroacetate (14) when treated with trifluoroacetic acid. ° ... 

Chlorination often exhibits second-order kinetics in acetic acid solution. In nonpolar solvents, the reaction is catalyzed by such added reagents as hydrogen chloride and trifluoroacetic acid, ° and exhibits complex kinetics. This rate behavior has been interpreted in terms of acid-catalyzed cleavage of the Cl-Cl bond in a chlorine-substrate complex. Chlorination is much more rapid in polar than in nonpolar solvents. Bromination also tends to exhibit complex kinetics in acetic acid... 

Write a mechanism for the acid-catalyzed cleavage of tert-hutyl cyclohexyl ether with trifluoroacetic acid to yield cyclohexanol and 2-methylpropene. 

This palladium-catalyzed three-component coupling reaction leading to the formation of aryl-substituted allylic amines was recently adapted to solid-phase synthesis (Scheme 8.23). Amines were chosen to attach to a solid support (Rink resin) in this three-component coupling process and were reacted with a variety of aryl halides and linear or cyclic non-conjugated dienes, the reaction being carried out at 100 °C for two days in the presence of palladium acetate and diisopropylethyl-amine. A wide variety of aryl-substituted allylic amines were then obtained after cleavage from the solid support by trifluoroacetic acid [60],... 

The first step of acid-catalyzed ether cleavage is protonation of the ether oxygen to give an intermediate oxonium ion, which collapses to form an alcohol and a tertiary carbocation. The carbocation then loses a proton to form an alkene, 2-methylpropene. This is an example of E elimination. The acid used for cleavage is often trifluoroacetic acid. 

Moiseev has reported the Co(II)/(III)-catalyzed oxidation of methane and ethane to alcohol derivatives by dioxygen in trifluoroacetic acid [28]. Interestingly, as in the case of oxidation in sulfuric acid, a significant amount of C-C cleavage products were obtained from ethane. A mechanism similar to that shown in Scheme 2 was proposed [28a]. 

In RPLC, acidic pH of 2.5-3 is used for many applications. The low pH suppresses the ionization of weakly acidic analytes, leading to higher retention.2,3,11 Surface silanols are not ionized at low pH, lessening tailing with basic solutes. Most silica-based bonded phases are not stable below pH 2 due to acid catalyzed hydrolytic cleavage of the bonded groups.23 Common acids used for mobile phase preparations are phosphoric acid, trifluoroacetic acid (TFA), formic acid, and acetic acid. However, basic analytes are ionized at low pH and might not be retained. 

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