The Pyridine Group

Furofuropyridines can be prepared from sugars. Starting from the doubly protected ribonolactone 67, after several steps involving addition of the pyridine group, deprotecting and other transformations, the fluoropyridyl-substituted... 

Wilson et al. [27] showed that the introduction of steric hindrance in the 6-position of one or two of the pyridine groups was sufficient to fine-tune the ligand field and obtain crossover compounds. These systems have been investigated using a number of different techniques, both in the solid and solution phases. Thermodynamic parameters have been derived from variable temperature magnetic susceptibility data for the single methyl-substituted (23 ) (AH°=19.7 kj mol"1, A5°=39.8 J mol"1 K"1), the double methylsubstitut-... 

FTIR revealed that hydrogen bonding decreased with heating above 100 °C, so at 190 °C almost all of the pyridine groups were not hydrogen bonded. 

When the ketone and olefin are unsymmetrical, two diasterio-isomeric oxetanes are formed. This point can be illustrated with the benzoylpyridines and norbornene, where the two stereoisomers result from the pyridine group being on the same or opposite side of the oxetane ring, with respect to the norbornane.37 In the case of 3-benzoyl-pyridine, the two isomers 49b and 50b were formed in about equal... 

We used partially crosslinked poly(4-vinyipyridine)(DBQP) as the polymer ligand. PVP was crosslinked by alkylation of the pyridine groups in PVP with 1,4-dibromobutane to yield insoluble DBQP resins. The free and unquaternized pyridine groups in DBQP could be used to form the polymer chelate, as represented in 33. 

Structure and Nomenclature. The pyridine group consists of a six-membered, heterocyclic, aromatic compound with one nitrogen atom in the ring. The parent compound of this group is pyridine I with ring positions numbered as shown. Alternative denotations of the I. 2, and 4 positions in the ring are alpha, heta, and gamma, respectively. 

Two independent molecules in the asymmetric unit. 6The S2 atom is trans to the pyridine group. Benzene solvate. 

Fig. 3.16 Radial distribution function (RDF) for one monolayer in compression, using as reference the pyridine group in relation to the distance of the counterion Br (—) 4.7 A, (,..)3.8A. (From ref. [81])...

FIGURE 5.11 Proposed mechanisms of participation of N heteroatoms in electrochemical processes on carbon surfaces (a) possible pseudo-Faradaic reaction of the pyridinic group in aqueous medium [95] (b) N-induced stabilization of carbene-like edge carbon atoms, sites responsible for the development of positive charge in acidic solution. 

The pyridine ring may contain additional heteroatoms, e.g. as diazines and triazines. These systems are subgrouped under the pyridine group according to the position of the... 

Poly(4-vinylpyridine-co-styrene-co- divinylbenzene) were supplied in the form of beads (Reillex 425 and Purolite ) or prepared as thin films (dimensions ca. 76 x 14 mm x 40-120 pm) at the University of Strathclyde.11 Quatemisation of the pyridine groups was carried out by slow addition of the polymer (typically 1 g) to ethanol (40 cm3) To this was added methyl iodide (2 cm3) and the mixture was heated to 50 °C for 2 hours and then cooled. The quatemised polymer was washed with ethanol followed by acetone and then vacuum dried. 

Photochromic anthrapyridones (IIB1, IIB2) were produced by cyclization of 1-chloracetylamino-4-(or -5)-phenoxyanthraquinones with the subsequent reductive elimination of the pyridine group from the products obtained in pyridine (Scheme 2).38 Photochromic chloro derivatives of pyridines (IIC) were synthesized by the interaction of the resultant photochromic anthrapyridines with phosphorous chlor-oxide.38... 

The position of the substituents on the pyridine moiety also affects the activity of the initiator. For example, p-MeO benzyl o-CN pyridinium salt 2k is 100 times more reactive than the corresponding p-CN derivative 2f. Thus, introduction of the o-cyano group into pyridine nucleo causes a large enhancement of the initiator activity. The reason for the activity enhancement by this modification can be accounted for by both electronic and steric effects of the o-cyano group of the pyridine group. In a typical comparison of the initiation activities of p-CN 2f and m-COOMe 21 substituted p-methoxy benzyl pyridinium salts in the polymerization of GPE, it was observed that p-substituted salt 2f is approximately 10 times more reactive than the corresponding o-substituted salt 21. In this case the steric effect of the substituents is negligible. A similar... 

It is worth mentioning straightaway that the e values found by best fit procedures to spectral and magnetic data do indeed tend to support this qualitative view. It has been found that for ammonia and tertiary amines one can consistently associate vanishing e values for these ligands in various complexes. In M(pyridine)4(NCS)2 M=Co(II), Fe(II), the e parameters defined in the planes of the pyridine groups are zero and take small (positive) values (ca. 100 cm ) perpendicular to these groups. By contrast, the... 

The pyridine group shows nucleojdiilic catalytic activity timilar to tiiat of imidazole. The use of partly protonated polyvinylpyridine as catalyst for flie solvolysis of anionic phenyl esters led to rate enhancements that were due to tiie coulonibic attraction, as mentioned before (51). 

The alkaloid nicotine is present in tobacco, Nicotiana tabacum. In discussing the derivatives of pyridine it was stated (p. 858) that the e/a-mono-carboxy acid of pyridine is known as nicotinic acid and that it is obtained by the oxidation of the alkaloid nicotine. Therefore the alkaloid undoubtedly contains the pyridine group. It has been synthesized by Pictet and its constitution established as a pyridine derivative of methyl pyrrolidine. This constitution was first suggested by... 

Fig. 22. A single sheet of U02(C6H804)(CioHgN2). Note the positions of the pyridine groups in comparison to trans H2O molecules seen in previous structures.

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