Hydrogen Bromide-Trifluoroacetic Acid

Dicyclohexy Icarbod iimide p-Toluenesulfonic Acid Phenyl Chloroformate Sodium Hydroxide Ethyl Chloroformate Sodium Carbonate Diphenyl Carbonate Benzyl Bromide iV,A-Dimethylacetamide Benzyl Chloride Acetonitrile Sodium Borohydride Trifluoroacetic Acid Hydrogen Cyanide Sodium Cyanide Sodium Bisulfite... 

Step n When the peptide is completely assembled it is removed from the resin by treatment with hydrogen bromide m trifluoroacetic acid... 

NKOH, EtOH, 20°, 5-10 min 80% yield. 5-2,2-Bis(carboethoxy)ethyl thioether, stable to acidic reagents such as trifluoroacetic acid and hydrogen bromide/acetic acid, has been used in a synthesis of glutathione. ... 

Acids that are used in addition to trifluoroacetic acid include trifluoroacetic acid with added sulfuric acid203 or boron trifluoride etherate,210,211 perfluorobu-tyric acid,212 hydrogen chloride/aluminum chloride,136,146,213 perchloric acid in chloroform,214 p-loluenesull onic acid alone134 or with aluminum bromide or aluminum chloride,192 concentrated sulfuric acid in two-phase systems with dichloromethane, alcohol, or ether solvents,209,215 trifluoromethanesulfonic acid,216 chlorodifluoroacetic acid,134 and the monohydrate of boron trifluoride... 

The next residues were attached successively by dicyclohexylcarbodiimide-mediated coupling of Boc-amino acids with the free amino groups. The use of excess Boc-amino acid eliminated the need for capping after coupling. The last Boc-group and the benzyl-based side chain and carboxy-terminal protectors were removed at the end of the synthesis by acidolysis with hydrogen bromide in trifluoroacetic acid the latter was used instead of acetic acid to avoid acetylation of hydroxymethyl side chains (see Section 6.6). Catalytic hydrogenolysis of the peptide removed the nitro... 

Aminopropanols, when reacted with cyanogen bromide, also afford 2-amino-(or imino)-dihydro-1,3-oxazines (Scheme 90) (64ZOB3427), and related thiazines are formed when allylic isothiouronium salts (207) are cyclized with trifluoroacetic acid and stannic chloride. The necessary starting materials are synthesized from aldehydes or ketones by the action of vinylmagnesium chloride and subsequent treatment of the product allyl alcohols (206) first with hydrogen chloride and then with a thiourea (Scheme 91) (77JHC717). 

The dipeptide is released from the polymer and the BOC-protecting group by adding hydrogen bromide (HBr) in trifluoroacetic acid. 

Triethylamine Hydrogen chloride Trifluoroacetic acid Sodium hydroxide n-Propyl bromide... 

Peptide chemists usually come from the eupeptic end of the scale of human felicity but anyone who performs the deprotection of a benzyl ester with 33% hydrogen bromide in acetic acid could be accused of brutality. That peptides survive is more a tribute to the molecules than the chemists who make them. The method is illustrated in Scheme 6.39.97 The reactivity of the benzyl ester can be augmented by adding a methoxy group to the para position. p-Methoxy-benzyl esters will cleave with trifluoroacetic acid in anisole or with a catalytic amount of trifluoroacetic acid in a phenol matrix at 45 °C.70... 

There are only a few reports in this area. Reaction of a pyrazolyl disulfide 377 with bromotrifluoromethane and ethyl bromide in the presence of sodium dithionite at room temperature afforded pyrazolyl sulfides 378. Oxidation of these with hydrogen peroxide in trifluoroacetic acid afforded sulfenylpyrazoles 379 in excellent yields (Scheme 41) <2006JFC(127)948>. Pyrazole-4-carbaldehyde 380 has been utilized in the efficient synthesis of... 

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