Copper-catalyzed enantioselective borylative cyclization with various electrophiles via difunctionalization of unsaturated hydrocarbons is a powerful tool for the generation of interesting ...boron-containing carbocycles and heterocycles processes involving a chiral organocopper intermediate. Alkenes, allenes, and alkynes are versatile and easily accessible substrates that can be subjected to a wide range of reactions to produce densely functionalized, enantioenriched products. In this chapter, I discuss copper-catalyzed alkenes, allenes, and alkynes borofunctionalization and enantioselective cyclization via chiral organocopper intermediate. Copper-catalyzed enantioselective borylative cyclization and regiodivergent functionalization of alkenes, allenes, and alkynes, as well as the current mechanistic understanding of such processes, are given special attention in this review.
Triple CH functionalization: Palladium‐catalyzed synthesis of benzofurans and coumarins by reacting phenols and unactivated olefins is described. The reaction comprises sequential CH ...functionalization and shows diverse functional group compatibility. Preliminary mechanistic studies shed light into the possible mechanisms.
We developed an operationally simple method for the direct use of biomass‐derived chemical entities in a fundamentally important process, such as hydrogenation. Various carbohydrates, starch, and ...lignin were used for stereoselective hydrogenation. Employing a transition metal catalyst and a novel catalytic system, the reduction of alkynes, alkenes, and carbonyl groups with high yields was demonstrated. The regioselective hydrogenation to access different stereoisomers was established by simple variations in the reaction conditions. This work is based on an unprecedented catalytic system and represents a straightforward application of biomass as a reducing reagent in chemical reactions.
Sweet chemistry. A catalytic transfer hydrogenation using biomass‐derived carbohydrates as reagent is developed. Stereoselective and chemoselective hydrogenation of alkynes, alkenes, and carbonyl compounds is demonstrated. This work provides an operationally simple method for transfer hydrogenation and represents a new concept for the application of renewable biomass.
An efficient, enantio‐ and diastereoselective, copper‐catalyzed coupling of imines, 1,3‐enynes, and diborons is reported. The process shows broad substrate scope and delivers complex, chiral ...homopropargyl amines; useful building blocks on the way to biologically‐relevant compounds. In particular, functionalized homopropargyl amines bearing up to three contiguous stereocenters can be prepared in a single step.
The enantio‐ and diastereoselective, copper‐catalyzed three‐component coupling of imines, 1,3‐enynes, and diborons delivers complex, chiral homopropargyl amines; useful building blocks on the way to biologically‐ and medicinally‐relevant compounds. In particular, functionalized homopropargyl amines bearing up to three contiguous stereocenters can be prepared in a single step.
An indole conjugated thiophene–pyridyl ( ITP ) sensor for cyanide has been synthesized and characterized using NMR and mass spectroscopy. The selectivity of ITP has been explored in aqueous solution, ...and the resulting ratiometric fluorescence response toward CN − , among 11 different anions, was studied. The complexation of ITP–CN has been addressed using HRMS, 1 H-NMR, and UV-vis spectroscopy. ITP displays substantial dual changes in both its ratiometric emission and absorption spectra, exclusively in the presence of CN − in aqueous solution. This is due to the nucleophilic attack of the indolium group of ITP by CN − , which induces a ratiometric fluorescence change and consequently a large emission shift. DFT/TDDFT calculations were performed in order to demonstrate the electronic properties of ITP and the ITP–CN adduct. The resultant ITP–CN adduct was used as a secondary sensing chemo-ensemble for the detection of cyanophilic metal ion-containing molecules by removing CN − from ITP–CN and regenerating ITP with switch-on red fluorescence. For the practical application of the sensor, test strips based on ITP were made up, which could act as suitable and proficient kits for CN − testing and cell studies.
Nitroolefins are usually synthesized using the Henry reaction. Here we report an alternative metal-free decarboxylative nitration protocol for the preparation of the nitroolefins from α,β-unsaturated ...carboxylic acids using t-butylnitrite (t-BuONO) and TEMPO. α,β-Unsaturated carboxylic acids bearing β-aromatic and β-heteroaromatic substituents gave (E)-nitroolefins exclusively under mild conditions. A radical based pathway has been proposed for this decarboxylative nitration reaction.
An efficient, enantio‐ and diastereoselective, copper‐catalyzed coupling of imines, 1,3‐enynes, and diborons is reported. The process shows broad substrate scope and delivers complex, chiral ...homopropargyl amines; useful building blocks on the way to biologically‐relevant compounds. In particular, functionalized homopropargyl amines bearing up to three contiguous stereocenters can be prepared in a single step.
Aus Drei mach Eins: Die entio‐ und diastereoselektive Kupfer‐katalysierte Dreikomponenten‐Kupplung von Iminen, 1,3‐Eninen und Diborverbindungen liefert komplexe, chirale Homopropargylamine, nützliche Bausteine für biologisch und medizinisch relevante Verbindungen. Funktionalisierte Homopropargylamine mit bis zu drei benachbarten Stereozentren können in einem einzigen Schritt synthetisiert werden.
A novel annulation reaction between 2‐aminopyridine derivatives and arenes under metal‐free conditions is described. The presented intermolecular transformation provided straightforward access to the ...important pyrido1,2‐abenzimidazole scaffold under mild reaction conditions. The unprecedented application of the methyl group of methylbenzenes as a traceless, non‐chelating, and highly regioselective directing group is reported.
Disappearing Me: A novel selective annulation between 2‐aminopyridine derivatives and arenes under metal‐free conditions provides the important pyrido1,2‐abenzimidazole scaffold under mild reaction conditions. In this intermolecular reaction the methyl group of methylbenzenes serves as a traceless, non‐chelating, and highly regioselective directing group.
Organocatalytic annulation by functionalization of benzamide derivatives with alkynes has been developed. We report a new approach of cycloaddition under mild reaction conditions using simple ...catalysts, such as iodobenzene and peracetic acid, as oxidant. Those novel, mild reaction conditions provided a straightforward synthesis of isoquinolones with fast reaction rate. Notable selectivity in annulation of unsymmetrically disubstituted alkynes was demonstrated.
Annulation without hesitation: N‐alkoxybenzamides convert into isoquinolones smoothly and rapidly under organocatalytic conditions. The annulation of unsymmetrical diarylacetylenes proceeds with a high regioselectivity. The transformation is based on the hypervalent‐iodine mediated generation of nitrenium ions.
An economical approach to α‐CF3‐substituted ketones, which are important intermediates in synthetic and medicinal chemistry, employs olefins and the readily available Langlois reagent (CF3SO2Na). The ...reaction is operationally simple, proceeds at room temperature, and exhibits an excellent tolerance toward a wide variety of functional groups.
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