Ruthenium-catalyzed cross-dehydrogenative C–H bond alkenylations occurred efficiently in environmentally benign water, which was exploited for an oxidative phthalide synthesis with ample scope. ...Mechanistic studies provided strong evidence for the oxidative alkenylation to proceed by an irreversible C–H bond metalation via acetate assistance.
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Transition‐metal‐catalyzed hydroformylation reactions constitute one of the most powerful tools for CC bond formation in organic synthesis and represent an outstanding example of the application of ...homogeneous catalysis on an industrial scale. This process allows for the straightforward conversion of inexpensive chemical feedstock into broadly applicable aldehydes, which serve as major building blocks for numerous chemical products. These products are highly valuable for the chemical industry and used as plasticizers, detergents, and surfactants on a million ton scale. Moreover, aldehydes serve as versatile chemical intermediates for the production of fine chemicals and pharmaceuticals. Currently, most of the bulk hydroformylation processes rely on rhodium‐based catalysts. The increasing demand and resulting high cost of this precious metal has resulted in alternative transition‐metal catalysts becoming highly desirable. The following Review summarizes the progress achieved utilizing Ru, Ir, Pd, Pt, and Fe catalysts in hydroformylation reactions.
New possibilities: There is a growing awareness that organometallic complexes based on ruthenium, iridium, palladium, and even iron as the central metal offer new opportunities for catalytic hydroformylations (see scheme; TM=transition metal). Research from the past few decades is critically summarized in this Review.
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This review summarizes the utilization of heteroarene N‐oxides as oxidant in organic reactions. The specific focus lies on reactions in which pyridine N‐oxides are used as oxygen source in an oxygen ...atom transfer fashion. The scope comprises the hydroxylation of aliphatic and aromatic C–H bonds, epoxidation as well as oxygenations of alkenes and alkynes. The latter have been extensively reviewed elsewhere and are merely discussed in a conceptual manner.
Heteroarene N‐oxides can be used as transfer oxygenation agents in organic synthesis. The application of N‐oxides as mild oxygen source for the oxygenation of aliphatic and aromatic hydrocarbons as well as unsaturated substrates is reviewed.
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The decarboxylative Giese-type reaction offers a versatile methodology for the radical alkylation of electron-deficient alkenes. Photo-mediated variants often require a pre-activation of carboxylic ...acids and/or employment of costly transition-metal photocatalysts. Herein, we present a metal-free photocatalyzed decarboxylative Giese-type addition to electron-deficient alkenes using pyrimidopteridine N-oxides as organic photoredox-active catalysts. This protocol comprises mono-, di-, and trisubstituted aliphatic, α-amino, and α-oxy acids as well as a variety of electron-deficient alkenes. Moreover, post-synthetic derivatization and applications are presented.
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A concise synthesis of (+)-pancratistatin and (+)-7-deoxypancratistatin from benzene using an enantioselective, dearomative carboamination strategy has been achieved. This approach, in combination ...with the judicious choice of subsequent olefin-type difunctionalization reactions, permits rapid and controlled access to a hexasubstituted core. Finally, minimal use of intermediary steps as well as direct, late stage C-7 hydroxylation provides both natural products in six and seven operations.
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We describe the development of an arenophile-mediated, nickel-catalyzed dearomative trans-1,2-carboamination protocol. A range of readily available aromatic compounds was converted to the ...corresponding dienes using Grignard reagents as nucleophiles. This strategy provided products with exclusive trans-selectivity and high enantioselectivity was observed in case of benzene and naphthalene. The utility of this methodology was showcased by controlled and stereoselective preparation of small, functionalized molecules.
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First things first: The title reaction of arenes bearing ortho‐directing groups (DG) in the presence of a ruthenium catalyst and aryl iodide is presented. The reaction is general for variously ...substituted aryl iodides to give ketones in moderate to good yields, and water serves as the solvent. The system is highly selective towards the mono‐carbonylative arylation by ortho CH functionalization. cod=cyclo‐1,5‐octadiene.
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A dearomative reduction of simple arenes has been developed which employs a visible‐light‐mediated cycloaddition of arenes with an N‐N‐arenophile and in situ diimide reduction. Subsequent ...cycloreversion or fragmentation of the arenophile moiety affords 1,3‐cyclohexadienes or 1,4‐diaminocyclohex‐2‐enes, compounds that are not synthetically accessible using existing dearomatization reactions. Importantly, this strategy also provides numerous opportunities for further derivatization as well as site‐selective functionalization of polynuclear arenes.
Light it up: A dearomative strategy based on the visible‐light‐promoted para‐cycloaddition of arenophile with arenes and in situ diimide reduction was developed that provides access to 1,3‐cyclohexadienes or unsaturated 1,4‐diamines. These products are complementary to known dearomative processes and are amenable to further diversification.
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Ambroxol (ABX) is a mucolytic agent used for the treatment of respiratory diseases. Bioactivity has been demonstrated as an enhancement effect on lysosomal acid β-glucosidase (β-Glu) activity in ...Gaucher disease (GD). The positive effects observed have been attributed to a mechanism of action similar to pharmacological chaperones (PCs), but an exact mechanistic description is still pending. The current study uses cell culture and in vitro assays to study the effects of ABX on β-Glu activity, processing, and stability upon ligand binding. Structural analogues bromohexine, 4-hydroxybromohexine, and norbromohexine were screened for chaperone efficacy, and in silico docking was performed. The sugar mimetic isofagomine (IFG) strongly inhibits β-Glu, while ABX exerts its inhibitory effect in the micromolar range. In GD patient fibroblasts, IFG and ABX increase mutant β-Glu activity to identical levels. However, the characteristics of the banding patterns of Endoglycosidase-H (Endo-H)-digested enzyme and a substantially lower half-life of ABX-treated β-Glu suggest different intracellular processing. In line with this observation, IFG efficiently stabilizes recombinant β-Glu against thermal denaturation in vitro, whereas ABX exerts no significant effect. Additional β-Glu enzyme activity testing using Bromohexine (BHX) and two related structures unexpectedly revealed that ABX alone can refunctionalize β-Glu in cellula. Taken together, our data indicate that ABX has little in vitro ability to act as PC, so the mode of action requires further clarification.
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A ruthenium‐catalyzed carbonylative CH bond arylation process for the three‐component synthesis of complex aryl–(hetero)aryl ketones in an aqueous solution has been developed. By exploiting the ...ortho‐activating effect of nitrogen‐containing directing groups, a regioselective, successive twofold C(sp2)C(sp2) bond formation has been achieved. This straightforward catalytic process provides access to versatile products prevalent in multiple bioactive compounds and supplies a valuable functional group for subsequent transformations.
CH bond functionalization: A ruthenium‐catalyzed carbonylative CH bond arylation process for the three‐component synthesis of complex aryl–(hetero)aryl ketones in an aqueous solution has been developed (see scheme). By exploiting the ortho‐activating effect of nitrogen‐containing directing groups, a regioselective, successive twofold C(sp2)C(sp2) bond formation has been achieved.
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