Phenylpyridine-W-oxide

Conditions (a) 1-5 mol% catalyst, w-CPBA/NMO, -78°C, CH2CI2. (b) 1-5 mol% catalyst, NaOCl, 4-phenylpyridine iV-oxide, 0°C, CH2CI2. (c) 1-5 mol% catalyst, NaOCl, pyridine iV-oxide, 0°C, CH2CI2. (d) Solvent = diethyl ether... 

The acidification of H2 may also be involved in hydrogenase action, where H2 is beheved to bind to an Fe(II) center. Isotope exchange between H2 and D2O is catalyzed by the enzyme see Nickel Enzymes Cofactors Nickel Models of Protein Active Sites Iron-Sulfur Proteins). Similar isotope exchange can also occur in H2 complexes. Oxidative addition to give a classical dihydride is also a common reaction. [W(H2)(CO)3(PCy3)2] is in equilibrium with about 20% of the dihydride in solution. This can lead to subsequent hydrogenolysis of M-C bonds as in the case of a cyclometallated phenylpyridine complex of Ir(III). ... 

The actual location of the —COOH group at carbon 3 was established by Skraup and CobenzD by physical and chemical criteria. Through a series of steps 3 phenylpyridine is prepared from j >-naphthylamine and glycerine, and upon oxidation it yields nicotinic acid. Skraup and Vortmanni, also prepared nicotinic acid from synthetic dipyridyl of known w-structure. The three position isomers have very different melting points picolinic acid (0-, or 1,2) around 136° nicotinic acid m- or 1,3-) around 236° and isonicotinic acidi p- or 1,4-) iiround 319°. 

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