Copper-diamine-catalyzed N-arylation of pyrroles, pyrazoles, indazoles, imidazoles, and triazoles

This paper details the copper-catalyzed N-arylation of pi-excessive nitrogen heterocycles. The coupling of either aryl iodides or aryl bromides with common nitrogen heterocycles (pyrroles, pyrazoles, indazoles, imidazoles, and triazoles) was successfully performed in good yield with catalysts derived from diamine ligands and CuI. General conditions were found that tolerate functional groups such as aldehydes, ketones, alcohols, primary amines, and nitriles on the aryl halide or heterocycle. Hindered aryl halides or heterocycles were also found to be suitable substrates using the conditions reported herein.     

Ruthenium-catalyzed enantioselective carbon-carbon bond forming reaction via allenylidene-ene process: synthetic approach to chiral heterocycles such as chromane, thiochromane, and 1,2,3,4-tetrahydroquinoline derivatives

Our previously disclosed ruthenium-catalyzed carbon-carbon bond forming reactions between propargylic alcohols and alkenes via an allenylidene-ene type pathway have been successfully applied to an enantioselective intramolecular cyclization for a variety of chiral heterocycles such as chromane, thiochromane, and 1,2,3,4-tetrahydroquinoline derivatives (up to 99% ee) by use of a suitable optically active diruthenium complex as a catalyst. The methodology described in this paper becomes a novel synthetic approach to chiral heterocycles, the structures of which are widely found in many natural and biologically active compounds.     

Aqueous N-heterocyclization of primary amines and hydrazines with dihalides: microwave-assisted syntheses of N-azacycloalkanes, isoindole, pyrazole, pyrazolidine, and phthalazine derivatives

[reactions: see text] The synthesis of nitrogen-containing heterocycles from alkyl dihalides (ditosylates) and primary amines and hydrazines via a simple and efficient cyclocondensation in an alkaline aqueous medium that occurs under microwave irradiation is described. This improved greener synthetic methodology provides a simple and straightforward one-pot approach to the synthesis of a variety of heterocycles, such as substituted azetidines, pyrrolidines, piperidines, azepanes, N-substituted 2,3-dihydro-1H-isoindoles, 4,5-dihydropyrazoles, pyrazolidines, and 1,2-dihydrophthalazines.     

The synthesis of chromenes, chromanes, coumarins and related heterocycles via tandem reactions of salicylic aldehydes or salicylic imines with alpha,beta-unsaturated compounds

The tandem reactions of salicylic aldehydes or salicylic imines with alpha,beta-unsaturated compounds have only been studied systematically in recent years. These tandem reactions provide an easy access to a variety of heterocycles, such as chromanes, chromenes, coumarins and tetrahydroxanthenones, many of which are synthetic useful intermediates.     

Development,Scope, and Applications of Titanium(III)-Catalyzed Cyclizations to Aminated N-Heterocycles

The exceptionally mild conditions of a titanium(III)-catalyzed cyclization reaction paired with a convenient acid/base extraction have enabled the straightforward synthesis, isolation, and direct N-functionalization of amino heterocycles such as 3-aminoindoles and -pyrroles. The unprotected heterocycles are ideal building blocks for the installation of aminated indoles and pyrroles into target molecules, but their sensitivity has previously impeded their synthesis by modern catalytic methods. This full paper presents the development and extended scope of the new cyclization methodology. The transformation of the products into fused bis-indoles is also demonstrated along with the discovery of an unusual palladium-catalyzed reductive biphenyl coupling reaction. The titanium(III)-catalyzed cyclization has also been applied to the synthesis of substituted 3-iminoindolines, which are of potential interest for applications in natural product synthesis and exhibit tunable blue-to-green fluorescence properties.     

The enantioselective intramolecular aminative functionalization of unactivated alkenes, dienes, allenes and alkynes for the synthesis of chiral nitrogen heterocycles

The enantioselective intramolecular aminative functionalization of unactivated alkenes and related π-systems is a straight-forward and atom economical strategy for the synthesis of chiral nitrogen heterocycles. These reactions can be categorized as oxidatively neutral, such as alkene hydroamination, or as oxidative reactions, such as alkene difunctionalization, e.g. aminooxygenation and carboamination. This perspective reviews the current work in the field and explores mechanistic trends that are common among the different catalysts and reaction types.     

Sodium Phosphaethynolate as a Building Block for Heterocycles

Phosphorus‐containing heterocycles have evolved from laboratory curiosities to functional components, such as ligands in catalytically active metal complexes or molecular constituents in electronic devices. The straightforward synthesis of functionalized heterocycles on a larger scale remains a challenge. Herein, we report the use of the phosphaethynolate (OCP)^? anion as a building block for various sterically unprotected and functionalized hydroxy substituted phosphorus heterocycles. Because the resulting heterocycles are themselves anions, they are building blocks in their own right and allow further facile functionalization. This property may be of interest in coordination chemistry and material science.     

Production of pyrans, pyridazines, pyrimidines, pyrazines and triazine compounds using benzoylacetonitriles as a precursor

Benzoylacetonitriles are easily available and have high chemical reactivity due to the presence of three active moieties; nitrile, carbonyl, and active methylene functions. This review article represents a survey covering the synthetic strategies leading to five six-membered heterocycles; pyrans, pyridazines, pyrimidines, pyrazines, and triazine compounds; utilizing benzoylacetonitriles as starting precursor since 1985. The reactions are subdivided into groups that cover the synthetic methods of these heterocycles.     

Preparation of new polyfunctional magnesiated heterocycles using a chlorine-, bromine-, or iodine-magnesium exchange

The reaction of heteroaryl iodides with i-PrMgBr (ca. 1.0 equiv) in THF provides the corresponding magnesiated heterocycles. Functional groups such as an ester, cyano, or chloride functions are tolerated in these new Grignard reagents if the exchange can be performed below -20 degrees C. This is the case for all heterocycles bearing electron-withdrawing groups or chelating functions facilitating the iodine-magnesium exchange. In many cases, the exchange can be extended to heteroaryl bromides, and a case of a chlorine-magnesium exchange is described with tetrachlorothiophene. This new preparation of functionalized heteroarylmagnesium compounds provides after reaction with various electrophiles a new entry to a broad range of polyfunctional pyridines, imidazoles, furanes, thiophenes, pyrroles, antipyrines, and uracil derivatives. The application of the halogen-magnesium exchange in the solid phase allows the performance of solid-phase synthesis, with potential applications for combinatorial chemistry.     

Magnetic circular dichroism of cyclic π-electron systems—20 : Amino derivatives of indole,azaindoles, and purines

The simple perimeter model combined with PMO theory is used to rationalize and predict trends in MCD spectra of substituted azaindoles and similar heterocycles bearing a single electron-donating mesomeric substituent, such as serotonin and adenine.