Heterocyclic compounds catalysis

Heterocoagulation Heterocyclic Heterocyclic amines Heterocyclic azo dyes Heterocyclic compounds Heterocyclic dyes Heterocyclic polymers Heterocyclic thiophenes Heteroepitaxy Heterogeneous catalysis Heterogemte Heteroglycan Heterojunction... 

Use of chiral semicorrins and related nitrogen heterocyclic compounds as chiral ligands in asymmetric catalysis has been reviewed periodically. Interested readers are referred to the review by Pfaltz.102... 

The formation of oxygen-containing heterocyclic compounds is also a consequence of the Maillard reaction. Amines and amino acids have a catalytic effect upon the formation of 2-furaldehyde (5), 5-(hydroxy-methyl)-2-furaldehyde (11),2-(2-hydroxyacetyl)furan (44),2 and 4-hy-droxy-5-methyl-3(2//)-furanone (111) (see Ref. 214). This catalytic effect can be observed with several other non-nitrogenous products, including maltol. The amino acid or amine catalysis has been attributed to the transient formation of enamines or immonium ions, or the 1,2-2,3 eno-lization of carbohydrates. Of interest is the detection of A -(2-furoyl-... 

Abstract The purpose of this chapter is to present a survey of the organometallic chemistry and catalysis of rhodium and iridium related to the oxidation of organic substrates that has been developed over the last 5 years, placing special emphasis on reactions or processes involving environmentally friendly oxidants. Iridium-based catalysts appear to be promising candidates for the oxidation of alcohols to aldehydes/ketones as products or as intermediates for heterocyclic compounds or domino reactions. Rhodium complexes seem to be more appropriate for the oxygenation of alkenes. In addition to catalytic allylic and benzylic oxidation of alkenes, recent advances in vinylic oxygenations have been focused on stoichiometric reactions. This review offers an overview of these reactions... 

The formation of arylzinc reagents can also be accomplished by using electrochemical methods. With a sacrificial zinc anode and in the presence of nickel 2,2-bipyridyl, polyfunctional zinc reagents of type 36 can be prepared in excellent yields (Scheme 14) . An electrochemical conversion of aryl halides to arylzinc compounds can also be achieved by a cobalt catalysis in DMF/pyridine mixture . The mechanism of this reaction has been carefully studied . This method can also be applied to heterocyclic compounds such as 2- or 3-chloropyridine and 2- or 3-bromothiophenes . Zinc can also be elec-trochemically activated and a mixture of zinc metal and small amounts of zinc formed by electroreduction of zinc halides are very reactive toward a-bromoesters and allylic or benzylic bromides . ... 

Phase transfer catalysis (PTC), or more generally, applications of two-phase systems, is one of the most important recent methodological developments in organic synthesis. It is important because it simplifies procedures, eliminates expensive, inconvenient, and dangerous reactants and solvents, and also allows one to perform many reactions that otherwise proceed unsatisfactory or do not proceed at all. PTC has been reviewed,1-12 but only one review concerns the chemistry of heterocyclic compounds.13... 

Heterogeneous Catalysis in the Synthesis and Reaction of Heterocyclic Compounds S. Hillers, Katalitich Sintez i Prevrashcheniya Geterotsikl. Soedin. Geterogen. Kataliz, 1976, 9-19. 

Aromatic heterocyclic compounds such as the AMosyl pyrrole 17 can also be used with anhydride catalysis (acid might destroy the pyrrole). Regioselectivity is determined by acylation next to the nitrogen5 and cyclisation follows.6... 

Abstract Heterocyclic compounds have been synthesized by means of stoichiometric reagents under acidic or basic conditions. Recent progress of homogeneous transition-metal catalysis realizes a highly selective and atom-economical methodology for synthesis of heterocycles under neutral and mild conditions. This review highlights the recent advances in the area of ruthenium-catalyzed syntheses of heterocyclic compounds. 

Keywords Ruthenium catalysis Heterocyclic compounds Cyclization Carbon-heteroatom bond formation Carbon-carbon bond formation... 

This review outlines the recent advances in the synthesis of heterocyclic compounds utilizing ruthenium catalysts. The first part is devoted to the synthesis of heterocycles via carbon-heteroatom bond formations. Heterocyclic frameworks are also constructed by ring closure of heteroatom-tethered acyclic molecules. The second part covers the ruthenium-catalyzed carbon-carbon bond forming cyclizations yielding heterocycles. Other examples, in which ruthenium catalysis indirectly participates in heterocycle formation, are collected in the final section. Although a heterocyclic ring was formed without catalysis, ruthenium-catalyzed processes play pivotal roles in such examples. 

Ruthenium catalysis has been extensively explored during the past decade [114]. Newly developed carbon-carbon bond forming cyclizations such as [2+2+2] cycloaddition, RCMs, and cycloisomerizations have dramatically expanded the scope of heterocycle synthesis. Relatively unexplored catalytic carbon-heteroatom bond formations have also made significant contributions to this area. Further progress in ruthenium catalysis will not only improve the conventional synthetic methodologies, but will also open the way to an unprecedented class of heterocyclic compounds, which might have a significant potential as pharmaceuticals or functional materials. 

Apart from the role of cyclophanes as a model system for studying the electronic interaction between the aromatic moieties, chiral [2.2]paracyclophanes have also been utilized as planar chiral ligands in asymmetric catalysis. Recent advances and applications in this area have been reviewed [5, 6]. The synthesis of heterocyclic compounds based on [2.2]paracyclophane architecture, where the long-distance electronic communication and the planar chirality play significant roles in their application, has also been reported recently [7]. Although the preparation and application of chiral cyclophanes in asymmetric synthesis has attracted much attention for a long time, their chiroptical properties, especially the CD spectra, have rarely been paid attention or even completely ignored. 

Whether the theoretically interesting results will lead to applications of the new phosphaalkenes as synthones for the class of heterocyclic compounds or, in coordination chemistry, to animate catalysis research, will be answered in the future. 

Under microwave irradiation, carbazole reacted remarkably fast with a number of alkyl halides to give Af-alkyl derivatives of carbazole (82) (Bogdal et al., 1997). The reaction was carried out with high yields by simply mixing carbazole with an alkyl halide, which was adsorbed on potassium carbonate. A facile synthesis of a series of A-alkylpyrrolidino fullerenes (83) by phase transfer catalysis without solvent under microwave irradiation has been described by De la Cruz et al. (1998), while Adamczyk and Rege (1998) have illustrated the dramatic rate acceleration for A-sulfopropylation of heterocyclic compounds using 1,3-propane sultone under microwave irradiation affording the A-sulfopropylated compounds in 68-95% yield. 

Heterogeneous metal catalysis is the most useful general method for the deuteration and/or tritiation of heterocyclic compounds.57 It involves exchange between the organic substrate and isotopic hydrogen (as water, usually, or gas) in the presence of a Group VIII transition metal catalyst at temperatures up to 180° [Eq. (18)]. 

Both acid and base catalysis have been used extensively to catalyze exchange in aromatic, and to a lesser extent, heterocyclic molecules. In acid exchange, the most widely used catalysts are sulfuric acid,122,129, 131 phosphoric acid,132 trifluoroacetic acid5133 perchloric acid,134 aluminum chloride,135 and the phosphoric acid-boron trifluoride complex.132 These reactions constitute the simplest electrophilic substitution. The mechanism for such substitution in benzenoid compounds is now comparatively well understood 122 however, the problem of heteroaromatic electrophilic substitution is still being clarified and has led to renewed interest in acid-catalyzed exchange in heterocyclic compounds.122... 

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