Pyridines, literature reviews synthesis

The study of heterocyclic compounds constitutes a major endeavor in the fields of organic chemistry and the life sciences. Although numerous texts on the synthesis, structure, and reactivity of heterocyclic compounds have been written [1,2], the application of solid-acid catalysts to the synthesis of heterocyclic compounds is rarely emphasized in the literature. The authors of this section of the book have chosen not to pursue an exhaustive literature review-type approach to this topic but rather to cover selected areas of this subject from the viewpoint of an industrial chemist. More specifically, an account of the synthesis of pyridines is given which relies heavily on patent literature. Pyridine bases constitute a sizable semicommodity industry that provides a platform into the pyridine derivatives that are precursors to numerous fine chemicals. In addition, this section includes selected examples of the synthesis of non-pyridine heterocycles which might be of commercial importance. 

Irnidazo[ 1,2-tf ]py ridines were covered in CHEC(1984) <1984CHEC(6)613> along with others imidazoles fused to six-membered rings and they were reviewed together with imidazo[l,5- ]pyridines in CHEC-II(1996) <1996CHEC-II(8)249>. The chemical literature on this heterocycle is very abundant, due to its easy synthesis (most of the preparations use readily available 2-aminopyridines) and to the very broad spectrum of bioactivities displayed by many derivatives. A simple Beilstein search on the fully conjugated heterocycle (free sites everywhere) disclosed ca. 3000 hits for the past decade. Therefore, this chapter cannot be exhaustive in view of space limitations, but will mainly focus on the original synthetic methods that have appeared in the last decade. 

Pyridines and their benzo-derivatives have played an important role in the synthesis of biologically active synthetic and natural substances. As a result, the construction of this molecular architecture has attracted the attention of a diverse array of synthetic methodologies. Notably, transition metal catalysis, radical reactions and cycloaddition chemistry-based methods have been developed for the construction of this important ring system. Detailed herein is a summary of the methods developed for the synthesis of pyridines, quinolines, isoquinolines and piperidines that were disclosed in the literature in 2002. Rather than survey all existing methods for the construction of these compound classes, this review will serve as a supplement and update to the review published last year in this series. 

The two coupling reactions appear to have a common free-radical intermediate. Functional groups already in the aromatic compound, Axil, orient ortbo-para regardless of their nature. The reactions are most valuable for the preparation of biaryls of unequivocal structure when the hydrocarbon, Ar H, is unsubstituted. Good directions are given for the synthesis of p-bromobiphenyl (35%), and the literature of the reaction has been reviewed. Among the hydrocarbons prepared in this way are a- and yS-phenylnaphthalenes, o-, m-, and p-methylbiphenyls and m- and p-terphenyls. Thiophene and pyridine nuclei also have been aryl-ated. ... 

The intent of this chapter is to provide an update of pyridine and piperidine alkaloid literature since this topic was last covered in Volume 3 of this series [1], The approximate time period covered by this review is 1984-1994. Due to the wealth of information available, this review had to be somewhat selective. For example, with the exception of a few selected pyridine monoterpenes, alkaloids containing a pyridine or piperidine ring fused to another ring system were excluded. The focus of this review is placed on describing new compounds isolated, biosynthesis, and biological properties. Synthesis has not been emphasized in most cases reference is made to only the most recent syntheses. 

N-Subst. pyrrolidines. A 10 M soln. of BH3-dimethyl sulfide in THF added dropwise via syringe to a soln. of startg. succinamic ester in the same solvent under N2, the mixture refluxed 7-9 h, and quenched with methanol and 2 N NaOH N-phenylpyr-rolidine. Y 82%. The method failed for highly hindered amines. F.e. incl. N-subst. piperidines s. M.C. Venuti, O. Ort, Synthesis 1988, 985-8 review of pyrrole, pyrrolidine, piperidine, pyridine and azepine alkaloids (1986-7 literature) s. A.R. Pinder, Nat. Prod. Reports 6, 67-78 (1989). 

Abstract Present review contains recent literature data published since 2009 for 2012 as till 2009 font reviews on this held have been published. The methods of synthesis of 2-, 3-, 4-hnoropyildines, di-, tri-, polyfluoropytidines, perfluoroalkylpyridines and also flnoropyridines fnsed with carbo-, heterocycles are presented. Methods for synthesis of P snbstitnted pyridines for local radiotherapy of cancer and other biological active componnds are also presented. 

The present review contains the literature published since 2009 for 2012. TUI 2009 four reviews on this field have been published, completely [1, 2] or in part [3] devoted to methods syntheses C-F pyridines and perfluoroalkyl pyridines [2,4]. To display full information about synthesis fluorinated pyridines in the present review earlier classical works also are included. 

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