Pyridine and its Derivatives

A number of workers have studied the influence of electron-attracting and -withdrawing substituents on the position of absorption bands (see reference [ ] in the Appendix). An interesting use of solvent effects to identify the carbonyl frequencies of pyridines also has been reported (see reference in the Appendix). 

GROUP FREQUENCIES ASSOCIATED WITH THE C=0 STRUCTURAL UNIT 

Another example of the sensitivity of the G=0 vibration to the structural groups surrounding it is provided by the two general series of compounds (I) and (II). For series (I), where R is CH3, 

it can be seen that the C=0 vibration, while somewhat sensitive to environment, still maintains a fairly constant frequency position. It is therefore a very useful group frequency. If the experimental conditions are stated, then its position becomes a very exact parameter for a given compound. 

Only a few structural groups have group frequency vibrations in the region where the C=0 vibration appears. These include such 

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E. Khugsbeig, ed.. Pyridine and Its Derivatives, Inteiscience PubHsheis, Inc., New Yoik, 1960. 

Fluorinatton of graphite with fluorine gives graphite fluorides that have interesting properties, as recently reviewed [63]. Pyridine and its derivatives add elemental fluorine to form unstable N-fluoro adducts [14, 26, 64, 65]. These may decompose to 2-fluoropyndines [65] or be stabilized by treatment with inflate salts to form useful electrophilic fluonnating agents [64]... 

The intense activation of ortho positions by strongly electron-withdrawing groups has produced some interesting kinetic results in the base-catalysed exchange of pyridine and its derivatives. For the neutral molecule, exchange occurs... 

Tertiary amines can be converted to amine oxides by oxidation. Hydrogen peroxide is often used, but peroxyacids are also important reagents for this purpose. Pyridine and its derivatives are oxidized only by peroxyacids. In the attack by hydrogen peroxide there is first formed a trialkylammonium peroxide, a hydrogen-bonded complex represented as R3N-H202, which can be isolated. The decomposition of this complex probably involves an attack by the OH moiety of the H2O2. Oxidation with Caro s acid has been shown to proceed in this manner ... 

Analogous to the dithiophosphate complexes, cis octahedral complexes are formed with bident-ate ligands like phenanthroline, 2,2 -bipyridine, or tmeda and trans octahedral complexes are formed with monodentate ligands like pyridine and its derivatives. Some examples are mentioned with linear bidentate ligands like 4,4 -bipyridine, which build up ID chains by bridging the [NiL2] molecules.926-933... 

From 2002 to 2007, Kubiak and Janczak [27-30] and Sun s [31] groups investigated various symmetrical MPcs with pyridine and its derivatives 4-CP and 4-MP as two axial ligands. Six complexes in this series with crystal structures are reported. The crystal structures of MnPc(Py)2 (M = Mg (4), Mn (5), Co (6) or Fe (7)) complexes with axial pyridine ligands are isostructural. Another two compounds [FenPc(4-CP)2] 2(4-CP) (8) and [RunPc(4-MP)2] -2CHC13 (9) have similar molecular structures to 4-7. The central metal ions in these complexes lie at the inversion centres thus, the molecules are centrosymmetric. In the six complexes, the central metal ion and the four Niso atoms of the Pc(2-) ligands lie on a strict plane. The... 

That the true pyridine derivative is more basic than the dihydrocompound is connected with the fact that in the latter the NH-group is united to two doubly bound C-atoms. Yet also pyridine and its derivatives are but weak bases. 

More detailed reduction of pyridine and its derivatives is given in Schemes 31 and 32 (pp. 55,... 

Pyridine and its derivatives are technically-important fine chemicals. Their isolation from coal tar is decreasing, whereas their manufacture by synthetic methods has increased rapidly. The classical pathways to pyridine have been discussed by Abramovitch (74HC14-1-4). Many of them rely on the reaction of aldehydes or ketones with ammonia in the vapor phase. However, the condensation processes used suffer from unsatisfactory selectivity. Using soluble organocobalt catalysts of the type [YCoL] allows pyridine and a wide range of 2-substituted derivatives to be prepared selectively and in one step from acetylene and the appropriate cyano compound [Eq.(l)]. 

E. Klinsberg (ed,). Pyridine and its Derivatives, in Chemistry of Heterocyclic Compounds, suppl. 1-4, ed, A. Weissberger and E, C, Taylor, Wiley-Interscience, New York, 1960-1964. 

Adsorption of pyridine and its derivatives on different metal electrodes has been studied very intensively [11], both at polycrystalline Au surface and different... 

The results of some of the many aminations of pyridine and its derivatives that have been carried out appear in Table 14. Yields are quoted where possible but these should not be used for quantitative comparisons as reaction and work up conditions vary widely. 2-Alkylpyridines aminate at the vacant a-position, except when the substituent is very large. 2-f-Butylpyridine does not undergo the Chichibabin reaction, probably because the bulky 2-f-butyl group prevents adsorption on to the sodamide surface. In contrast, 2-phenylpyridine undergoes amination in very good yield. Aminations of 2- and 4-methyl-pyridines do not involve attack on the anhydrobases in aprotic solvents, but some ionization does take place in liquid ammonia. 4-Benzylpyridine forms a carbanion (148) which is only aminated with difficulty by a second mole of sodamide (equation 103). 

B-76MI20601 D. M. Smith Pyridine and Its Derivatives , in Rodd s Chemistry of Carbon... 

Pyridine (and its derivatives) are water-soluble and do not readily bind to organic constituents of soil and aquifer materials. They may, therefore, be transported through aquifer materials, sediments and soils and thus contaminate rivers and estuaries (Liu Kuo, 1997). 

Il)cycles formed with 2,2 -bipyridine or 1,10-phenanthroline type ligands to give a variety of target compounds (Scheme 18). These syntheses are more feasible than previous, where the complexes cis-[RuCl2(bpy)2] or fRuCl .(tpy)] have been used to cyclometalate 2-phenyl-pyridine and its derivatives (230-233). A bunch of diverse compounds have been prepared in good yields. Crystal structures of some of them are shown in Fig. 21 and their useful properties are summarized in Table IX. 

When the donor atom is a part of the aromatic system, one would expect more obvious differences in reactivity. At present relatively little comparative information is available on such heterocyclic systems. Only on pyridine and its derivatives are there any reasonably extensive data. For pyridine a wide variety of coordination processes are available and pyridine-N-oxide as well as metallic complexes and complexes with nonmetallic Lewis acids must be considered. For comparative purposes the great reluctance with which pyridine undergoes electrophilic... 

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