Pyridine and Related Compounds

The calculations reported here were carried out with the latest version of the MINDO/3 SCF MO program (12, 13) which is an improved version in the series of MINDO (14) -MIND072 (15, 16)-MTNDO/21 (17) methods. The powerful and fast DFP (12) optimization procedure allowed us to calculate the various structures without any geometrical restrictions. The same method was very successful in the case of the reduction and protonation processes of pyridine and related compounds (1). ... 

Hydrogenation of Heteroaromatic Compounds Pyridines and Related Compounds... 

Electron-poor aromatic hctcrocycles, such as pyridines and related compounds, are not reduced under ionic hydrogenation conditions. Therefore, this method is limited to the more reactive five-membered-ring heteroaromatics. 

We have developed a Lewis acid-catalyzed three-component condensation [299] between a 2-aminoazine, an aldehyde, and an isonitrile that affords 3-aminoimidazo[l,2-fl]pyridines and related compounds. This reaction was adapted to the solid phase [300] by anchoring any one of the three reactants to RAM resin 7c. Thus, 6-aminonicotinic and 3-formylbenzoic acids could be anchored to support 7c in the presence of HATU and subjected to the 3CC reaction. Alternatively, a resin-bound isonitrile was obtained by coupling 7-aminobutyric acid (GABA) to 7c, followed by for-mylation of the amino group and dehydration (Scheme 11). After the 3CC reaction, cleavage was effected using TFA-CH2CI2 (1 1). 

The synthesis of [2.2.3]cyclazines, aza[2.2.3]cyclazines and their derivatives has also been covered. The attention of the reviewers has been focused on the study of the developments in the synthesis of several benzocyclazines and azacyclazines by the [8 -I- 2] cycloaddition reaction of the dimethyl acetylene dicarboxylate with various types of indolizines. The synthesis of indolizines, imidazo[l, 2-a]pyridines, and related compounds, which are key intermediates for the synthesis of cyclazines, is also described <88H(27)225i>. 

Six-membered Systems with One Heteroatom 10.3.4.1 Synthesis of Pyridines and Related Compounds... 

Plevey, R.G. Rendell, R.W. Tatlow, J.C. Fluorinations with complex metal fluorides. Part 6. Fluorination of pyridine and related compounds with caesium tetrafluorocobaltate (111). J. Fluorine Chem. 1982, 21, 159-169. 

In the case of pyrrole, furan and thiophen, the six jr-electrons derive four from the carbon atoms and two (the lone pair ) from the hetero atom. For this reason Albert has termed these heterocyclic compounds Ti-exccssive, in contrast to pyridine, and related compounds, which are referred to as 7r-dejS.cient, because the hetero atom tends to withdraw jr-electrons from, the molecular orbitals and thus reduce the resonance energy. 

Snavely, D.L., Overly, J.A., and Walters, V.A., Vibrational overtone spectroscopy of pyridine and related compounds, Chem. Phys., 201, 567-574, 1995. 

Patent literature dealing with the alkylation of polyfluorinated pyridines and related compounds by carbanions generated in situ from fluoro-oleflns... 

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