Quinoxalines represent bicyclic nitrogen‐containing heterocycles with a wide array of applications. They exhibit a multitude of biological activities relevant in medicinal chemistry as well as a ...plethora of luminescence properties. Quinoxaline syntheses exploit the whole raft of multicomponent syntheses from domino to sequential or consecutive reactions, harvesting well‐known synthetic concepts and reactions, such as Ugi‐reactions, but also leading to the development of novel reactions and sequences. Diversity‐oriented synthesis and transition metal catalyzed multicomponent reactions open efficient pathways to quinoxalines and quinoxaline‐containing moieties in a one‐pot fashion. This review outlines the underlying reaction‐based principles of multicomponent syntheses of quinoxalines and summarizes recent developments quinoxaline‐directed MCRs, illustrating their scopes.
3d Transition Metals for C–H Activation Gandeepan, Parthasarathy; Müller, Thomas; Zell, Daniel ...
Chemical reviews,
02/2019, Volume:
119, Issue:
4
Journal Article
Peer reviewed
C–H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, ...among others. Despite major advances, the vast majority of these C–H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C–H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C–H activation until summer 2018.
CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the ...present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does not depend primarily on the absolute amount of CO2 emissions that can be remediated by a single technology. Rather, CO2-based chemistry is stimulated by the significance of the relative improvement in carbon balance and other critical factors defining the environmental impact of chemical production in all relevant sectors in accord with the principles of green chemistry.
The copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) is a highly versatile, regioselective synthesis of 1,4‐disubstituted 1,2,3‐triazoles under mild reaction conditions and has found numerous ...applications in medicinal, bioorganic, and materials chemistry in the past one and a half decades. By virtue of the enormous tolerance for functional groups and the mild reaction conditions, CuAAC has become increasingly important in combination with multicomponent reactions (MCR), either in a domino or in a consecutive fashion. While the majority of CuAAC‐based MCR are founded on the in situ or en route generation of azides, one‐pot generation of alkynes and the concatenation with other MCR are rapidly catching up and novel sequences for efficient one‐pot syntheses of triazole‐based structures in a multicomponent fashion are constantly evolving. This review summarizes important contributions of CuAAC‐based MCR including MCR‐type applications in polymer science.
A series of isomeric dithieno1,4thiazines is accessible through an intermolecular–intramolecular Buchwald–Hartwig amination starting from dihalodithienyl sulfides. The electronic properties of ...dithieno1,4thiazine isomers differ conspicuously over a broad range depending on the thiophene–thiazine anellation: a large cathodic (340 mV) or an anodic shift (130 mV) of the redox potentials relative to corresponding phenothiazines is possible. Structure–property relationships of the dithieno1,4thiazine constitution derived from DFT calculations and cyclic voltammetry not only reveal increased electron density but also different delocalization of the radical cations that determines the electrochemical properties significantly. In addition, photophysical properties (absorption and emission) qualify dithieno1,4thiazines as promising substitutes of phenothiazine and beyond due to increased tunable electron richness.
Structure–property relationships: Four isomeric dithieno1,4thiazines, thieno congeners of phenothiazines, are synthesized by inter‐intra‐molecular Buchwald–Hartwig coupling. Their electronic properties open new avenues as donor systems for molecular electronics.
The C−H thiolation of aniline derivatives was accomplished with a versatile nickel(II) catalyst under ligand‐free conditions. The robust nature of the nickel catalysis system was reflected by the C−H ...thiolation with a good functional group tolerance and an ample scope, employing anilines possessing removable directing groups. The widely applicable nickel catalyst also allowed for aniline C−H selenylations, while mechanistic studies provided strong support that the rate‐determining step is the C−H activation.
Freed from ligands! Expedient nickel‐catalyzed C−H thiolations of anilines were achieved under ligand‐free reaction conditions, which also enabled the site‐selective C−H selenylation with an ample scope through a removable directing‐group strategy.
A study investigated the multiconfiguration self-consistent field and multireference configuration interaction methods and applications to the field of chemistry. These methods are applicable to ...arbitrary electronics states and molecular configurations.
N‐Benzyl aroyl‐S,N‐ketene acetals can be readily synthesized by condensation of aroyl chlorides and N‐benzyl 2‐methyl benzothiazolium salts in good to excellent yields, yielding a library of 35 ...chromophores with bright solid‐state emission and aggregation‐induced emission characteristics. Varying the substituent from electron‐donating to electron‐withdrawing enables the tuning of the solid‐state emission color from deep blue to red.
A diverse library of 35 N‐benzyl aroylS,N‐ketene acetals with tunable color of the solid‐state emission and aggregation‐induced emission characteristics is readily synthesized by condensation of aroyl chlorides and N‐benzyl 2‐methyl benzothiazolium salts.
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