Picolinic acids

Rcolinic acid Is readily prepared by the oxidation of a-picoline with potas- 

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Trifluoromethylpyridine can be prepared ia 54% yield from picolinic acid and sulfur tetrafluoride—hydrogen fluoride (434). 2-Trifluoromethylpyridine is a weak base no hydrochloride salt is formed. However, 2-trifluoromethylpyridine 1-oxide [22253-71-0] (bp 132—133°C/2.7 kPa (20 mm Hg)) is prepared ia 81% yield usiag 30% hydrogen peroxide—acetic acid (438). 

Other auxin-like herbicides (2,48) include the chlorobenzoic acids, eg, dicamba and chloramben, and miscellaneous compounds such as picloram, a substituted picolinic acid, and naptalam (see Table 1). Naptalam is not halogenated and is reported to function as an antiauxin, competitively blocking lAA action (199). TIBA is an antiauxin used in receptor site and other plant growth studies at the molecular level (201). Diclofop-methyl and diclofop are also potent, rapid inhibitors of auxin-stimulated response in monocots (93,94). Diclofop is reported to act as a proton ionophore, dissipating cell membrane potential and perturbing membrane functions. 

The picolinamide is prepared in 95% yield from picolinic acid/DCC and an amino acid, and is hydrolyzed in 75% yield by aqueous Cu(OAc)2. ... 

Using the pK values of the 5-substituted picolinic acids (5-R-2-COOH) and the 6-substituted nicotinic acids (6-R-3-COOH), in 50% ethanol at 25°, considerably better correlations are observed, with p = 3.31 and 1.60, respectively. The transmission through the... 

Decarboxylation of crystalline isoxazole-3-carboxylic acids appears to proceed by another mechanism,probably with formation of a zwitterion (159) which reacts as in the case of picolinic acid de-... 

Siegmund I, Koenig K, Andreesen JR (1990) Molybdenum involvement in aerobic degradation of picolinic acid by Arthrobacterpicolinophilus FEMS Microbiol Lett 67 281-284. 

Tate RL, Ensign JC (1974) Picolinic acid hydroxylase of Arthrobacter picolinophilus. Can J Microbiol 20 695-702. 

Dagley S, PA Johnson (1963) Microbial oxidation of kynurenic, xanthurenic and picolinic acids. Biochim Biophys Acta 78 577-587. 

Interesting hydrocarbon oxidations have been observed using Fe(II) catalysts with oxygen or hydrogen peroxide as the oxidant. These catalytic systems have become known as Gif chemistry after the location of their discovery in France.287 An Oxidations improved system involving Fe(III), picolinic acid, and H202 has been developed. The... 

Preparation of ligand 31 Originally, chiral ligand 31 was prepared from (1R,2R)-1,2-diaminocydohexane 33 based on the racemic synthesis reported by Barnes et al. in 1978 [15], where picolinic acid 34 was activated with P(OPh)3 and then coupled with trans-l,2-diaminocyclohexane. The reported isolated yield in the case of racemate was only 47%. We optimized the preparation as shown in Scheme 2.8 [16]. Picolinic acid 34 was activated with CDI in THF. After confirmation of activation, chiral diamine 33 was added to the solution. When complete, the reaction was quenched via the addition of a small amount of water (to quench excess CDI). The reaction solvent was then switched from THF to EtOH, when the desired ligand 31 directly crystallized out. Ligand 31 was isolated in 87% yield by simple filtration of the reaction mixture in high purity. With a 22 litter flask, 1.25 kg of 31 was prepared in a single batch. 

To test this hypothesis, the picolinamide 22 was prepared using in situ activated picolinic acid (Scheme 8.12). The in situ activation of picohnic acid was used because picolinyl chloride (available commercially as the HC1 salt) is relatively expensive. The coupling reaction was not straightforward, and the best results were obtained by adding 1.4equiv of thionyl chloride to a solution of 1.4equiv of picolinic acid in acetonitrile, followed by addition of triethylamine. As soon as the addition of triethylamine was complete, aniline 5 was introduced immediately because the activated picolinic acid was unstable in the presence of triethylamine. 

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