Trifluorobenzoic acids

Then, to these crystals were added 18 N sulfuric acid (150 ml) and the mixture was heated for 3.5 h at 100°C. After cooling, water (400 ml) was added to the mixture and the resulting crystals were recrystallized from n-hexane to give the 3-methoxy-2,4,5-trifluorobenzoic acid (9.61 g) as colorless needle, melting point 98°-101°C. 

To 3-methoxy-2,4,5-trifluorobenzoic acid (9.4 g) was added thionyl chloride (50 ml), the mixture was refluxed for 3 h and then concentrated. The residue was purified by distillation under reduced pressure to give 3-methoxy-2,4,5-trifluorobenzoyl chloride (8.86 g) as yellow oil, boiling point 108°-112°C/20 mm Hg. 

Fluoro-4-iodoaniline (0.00791 mol) dissolved in 10 ml THF was cooled to —78°C, then treated with 6 ml 2.0 M lithium diisopropylamide in THF/heptane/ethylbenzene, and the suspension stirred 10 minutes. The mixture was further treated with 5-bromo-2,3,4-trifluorobenzoic acid (0.00392 mol) dissolved in 15 ml THF, then stirred 18 hours at ambient temperature, and concentrated. The residue was treated with 100 ml 10% HC1 and the suspension was extracted twice with 150 ml diethyl ether, then dried using MgS04. The solution was reconcentrated and an orange solid was isolated. The solid was triturated with boiling CH2C12, then cooled. The solid was isolated by filtration, then rinsed with CH2C12, and the product isolated, mp = 200—201°C. 

C8H4CIF30 4-chloro-3-(trifluoromethyl)benzaldehyde 34328-46-6 491.15 43 034 1,2 12666 C8H5F303 3-methoxy-2,4,5-trifluorobenzoic acid 11281-65-5 476.15 TTsiT 2... 

C-8 chlorine derivatives appear more difficult to synthetize [24, 26, 31], the main issue being the introduction of the chlorine atom. Access to 3-chloro-2,4,5-trifluorobenzoic acid was achieved by a pivotal fluorine exchange reaction from 2,3,4-trichloro-5-fluorobenzonitrile or by direct chlorination of 2,4,5-trifluoro-benzoic acid. 

Anquetin G, Greiner J, Vierling P (2005) Synthesis of mono- and di-substituted 2,4,5-trifluorobenzoic acid synthons, key precursors for biologically active6-fluoroquinolones. Tetrahedron 61 8394-8404... 

It has been shown that the presence of catalytic amounts of carboxylic acid such as trani-l,2-cyclohexyldicarboxylic or 3,4,5-trifluorobenzoic acid improved the ruthenium-catalysed sp C-H bond alkylation of cyclic amines by terminal olefins and allowed reaching full conversion of less reactive A -pyridylpiperidine derivatives. Thus, in the absence of CO but in the presence of tra s-l,2-cyclohexyldi-carboxylic acid, the A -pyridylpiperidine 38 was efficiently hexylated into mono- 39 and dialkylated 40 piperidine derivatives, whereas in the absence of carboxylic acid... 

---