CF3COOH

Costain C C and Srivastava G P 1961 Study of hydrogen bonding miorowave speotra of CF3COOH-HCOOH J. Chem. Phys. 35 1903-4... 

Cleavage - with strong protic acid (3M HCl, CF3COOH)... 

CF3COOH, H2O, 20°, 48 h, 85-90% yield. The r-butoxymethyl ether is stable to hot glacial acetic acid aqueous acetic acid, 20° and anhydrous trifluoroacetic acid. 

The tetrahydrothiopyranyl ether was prepared from a 3-hydroxy steroid and dihy-drothiopyran (CF3COOH, CHCI3, 35% yield) it can be cleaved under neutral conditions (AgN03, aq. acetone, 85% yield). ... 

Dihydrothiofuran, CHCI3, CF3COOH, reflux, 6 days, 15% yield. r yc cat. TsOH, CHCI3, 20°,5h, 85-95%yield. ... 

Ph2CHO)3PO, cat. CF3COOH, CH2CI2, reflux, 4-9 h, 65-92% yield. This methodology has been applied to the protection of amino acid alcohols. ... 

CF3COOH, anisole, CH2Cl2. Anisole is present to scavenge the diphenylmethyl cation liberated during the cleavage reaction. 

CF3COOH, r-BuOH, 20°, 2-30 min, then Bio-Rad 1x2 (OH ) resin.These conditions were used to cleave the trityl group from the 5 -hydroxyl of a nucleoside. Bio-Rad resin neutralizes the hydrolysis and minimizes cleavage of,glycosyl bonds. 

CH(OMe>3, MeN02, CF3COOH, reflux, 4 h, 81-93% yield. This procedure was reported to be particularly effective for the preparation of ketals of diaiyl ketones. 

A phenacyl ester is much more readily cleaved by nucleophiles than are othc esters such as the benzyl ester. Phenacyl esters are stable to acidic hydrolysis (e.g coned. HCh HBr/HOAc 50% CF3COOH/CH2Cl2 HF, 0°, 1 h ). 

Cycloalkyl esters have.been used to protect the /3-CO2H group in aspartyl peptides to minimize aspartimide formation during acidic or basic reactions. Aspartimide foimation is limited to 2-3% in TFA (20 h, 25°), 5-7% with HF at 0°, and 1.5-4% TfOH (thioanisole in TFA). Cycloalkyl esters are also stable to Et3N, whereas use of the benzyl ester leads to 25 % aspartimide formation during Et3N treatment. Cycloalkyl esters are stable to CF3COOH, but are readily cleaved with HF or TfOH. - ... 

Ph2CHO)3PO, CF3COOH, CH2CI2, reflux, 1-5 h, 70-87% yield. Free alcohols are converted to the corresponding Dpm ethers. This reaction has also been used for the selective protection of amino acids as their tosylate salts (CCI4, 15 min-3 h, 63-91% yield). ... 

This derivative is prepared from an A-protected amino acid and the anthrylmethyl alcohol in the presence of DCC/hydroxybenzotriazole. It can also be prepared from 2-(bromomethyl)-9,10-anthraquinone (Cs2C03). It is stable to moderately acidic conditions (e.g., CF3COOH, 20°, 1 h HBr/HOAc, / 2 = 65 h HCl/ CH2CI2, 20°, 1 h). Cleavage is effected by reduction of the quinone to the hy-droquinone i in the latter, electron release from the —OH group of the hydroqui-none results in facile cleavage of the methylene-carboxylate bond. The related 2-phenyl-2-(9,10-dioxo)anthrylmethyl ester has also been prepared, but is cleaved by electrolysis (—0.9 V, DMF, 0.1 M LiC104, 80% yield). ... 

The p-bromobenzyl ester has been used to protect the /3-COOH group in aspartic acid. It is cleaved by strong acidic hydrolysis (HF, 0°, 10 min, 100% yield), but is stable to 50% CF3COOH/CH2CI2 used to cleave /-butyl carbamates. It is 5-7 times more stable than a benzyl ester. ... 

The piperonyl ester can be prepared from an amino acid ester and the benzyl alcohol (imidazole/dioxane, 25°, 12 h, 85% yield) or from an amino acid and the benzyl chloride (Et3N, DMF, 25°, 57-95% yield). It is cleaved, more readily than a p-methoxybenzyl ester, by acidic hydrolysis (CF3COOH, 25°, 5 min, 91% yield). ... 

A polymer-supported sulfonamide, prepared from an amino acid activated ester and a polystyrene-sulfonamide, is stable to acidic hydrolysis (CF3COOH HBr/ HOAc). It is cleaved by the safety-catch method shown below. ... 

Electrolytic reduction, 0.25 M H2SO4, 88% yield. 5-4-Picolylcysteine is stable to CF3COOH (7 days), to HBr/AcOH, and to 1 M NaOH. References for the electrolytic removal of seven other protective groups are included. ... 

CF3COOH, 2.5% phenol, 30°, 2 h, 65% yield. Zervas and co-workers tried many conditions for the acid-catalyzed formation and removal of the 5-diphenyl methyl, 5-4,4 -dimethoxydiphenylmethyl, and 5-tripheny I methyl thioethers. The best conditions for the 5-diphenylmethyl thioether are shown above. Phenol or anisole act as cation scavengers. 

Triphenylmethyl thioethers have been formed by reaction of the thiol with tri-phenylmethyl alcohol/anhydrous CF3COOH (85-90% yield) or with triphenyl-methyl chloride (75% yield). 

Isobutylene, H2SO4, CH2CI2, 25°, 12 h, 73% yield. The 5-/-butyl derivative of cysteine is stable to HBr/AcOH and to CF3COOH. 

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