C—CF3COOH

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

Reaction of 8-substituted 3-[2-(4-methoxybenzyl)-2//-tetrazol-5-yl]-4//-pyrido[l,2-u]pyrimidin-4-ones with CF3COOH for 2 days at room temperature gave 3-(2//-tetrazol-5-yl) derivatives (OlMIPl). The cyano group of a 3-(8-substituted 2-hydroxy-4-oxo-4//-pyrido[l,2-u]pyrimidin-3-yl)-2-propenenitrile was converted into a 5-tetrazolyl group by treatment with NaN3 in the presence of AICI3 in DMF at 100 °C for 2 days. 

From this work the relative efficiencies of Bronsted acids, in the presence of stannic chloride (0.166 M) in promoting hydrogen exchange at 25 °C can be ascertained from the rate coefficients (106Art) as follows HC1 (44) H20 (27) AcOH (1.6) CF3COOH (very small). Thus the ability of the dual acid systems to transfer protons is not simply related to the conventional acid strength of the BrQnsted component. 

FIRST-ORDER RATE COEFFICIENTS FOR THE REACTION OF [2H]-C6Me5 WITH CF3COOH IN THE PRESENCE OF APROTIC SOLVENTS AT 25 °C 543... 

Ring nitrosation with nitrous acid is normally carried out only with active substrates such as amines and phenols. However, primary aromatic amines give diazonium ions (12-47) when treated with nitrous acid, " and secondary amines tend to give N-nitroso rather than C-nitroso compounds (12-49) hence this reaction is normally limited to phenols and tertiary aromatic amines. Nevertheless secondary aromatic amines can be C-nitrosated in two ways. The N-nitroso compound first obtained can be isomerized to a C-nitroso compound (11-32), or it can be treated with another mole of nitrous acid to give an N,C-dinitroso compound. Also, a successful nitrosation of anisole has been reported, where the solvent was CF3COOH—CH2CI2. " ... 

Scheme 4.15 Carroll (-)-epibatidine synthesis plan (1995). (a) Heat (78%) (b) EtOH, 2[Ni(OAc)2 4H2OI, 4NaBH4, then 4HCI, 4H2O (96%) (c) 5Na, 4MeOH (65%) (d) heat, KOfBu, fBuOH (46%) (e) CH2CI2, CF3COOH (cat.), then H2O (97%).

Scheme 32. Indenobenzazepines from the 8,14-cycloberbine 146. Reagents a, H+, H20, or MeOH b, HCHO c, NaBH3CN d, TiCl4 or BF3 OEt2 e, I2, EtOH or AcOH or CF3COOH, benzene or p-TsOH, benzene. 

Scheme 94. Synthesis of chilenine (380) and its conversion to related alkaloids. Reagents a, aq NH3 b, py-HCl, py c, Zn, HCl-AcOH d, NaBH4 e, Mel, MeOH f, AcOH g, NaOH, aq MeOH h, CF3COOH.

Scheme 4-34. Reagents and conditions a 0s04-(— )-102/THF (96%). b Et3SiH/ CF3COOH (78%). c Pyridine-S03-NEt3/DMSO (87%). d o-C6H4(COC1)2-A1C13/ PhN02, (76%, 53% after recrystallization).

The hydroxylation of C-H bonds by radicals, in contrast to the case of electrophilic oxidants, leads to alcohols without retention of stereochemical configuration. H202, activated by strong acids (superacids (277), HF-BF3 (272), A1C13 (213), and CF3COOH (214)) have been used for the hydroxylation of aromatic compounds. These acid-catalyzed hydroxylations cannot be applied for aliphatic reactants because the hydroxylated products are more reactive than the starting compounds and, hence, they are oxidized further. 

Ionic hydrogenation of the same bicyclic diene 382 by Et3SiH in the presence of CF3COOH at room temperature or at 80 °C via ions 387 and 388 is accompanied by transannular cyclizations (equation 139)192. The behavior of diene 382 under Ritter reaction conditions (MeCN, H2SO4) reveals new possibilities to control the transannular cyclizations (equation 140)193. Depending on the sulfuric acid concentration, the reaction temperature and the presence of a nucleophilic solvent, these transformations can be directed to the formation of either the bicyclic amides 389 and 390 having the precursor structure or the tricyclic products 391193. 

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