A cationic cobalt(III)‐catalyzed direct CH amidation of unactivated (hetero)arenes and alkenes by using 1,4,2‐dioxazol‐5‐ones as the amidating reagent has been developed. This transformation ...proceeds efficiently under external oxidant‐free conditions with a broad substrate scope. Moreover, 6‐arylpurine compounds, which often exhibit high potency in antimycobacterial, cytostatic, and anti‐HCV activities, can be smoothly amidated, thus offering a mild protocol for their late stage functionalization.
Operationally simple: A cationic cobalt(III) catalyzed direct CH amidation of unactivated (hetero)arenes and alkenes has been developed (see scheme; DCE=1,2‐dichloroethane). This reaction proceeded efficiently under external oxidant‐free conditions with ample substrate scope, as well as excellent chemo‐ and regioselectivity. Moreover, 6‐arylpurine compounds, which often exhibit important biological activities, can be smoothly modified by this mild protocol.
Manganese photocatalysts enabled versatile room‐temperature C−H arylation reactions by means of continuous visible‐light photoflow, thus allowing for efficient C−H arylations in 30 minutes with ample ...scope. The robustness of the manganese‐catalyzed photoflow strategy was shown by visible light‐induced gram‐scale synthesis, clearly outperforming the batch performance.
Photochemistry in the flow: Earth‐abundant manganese catalysts enabled visible‐light‐induced C−H arylations at room temperature in a continuous photoflow manifold.
A transition‐metal‐free Cs2CO3‐catalyzed α‐hydroxylation of carbonyl compounds with O2 as the oxygen source is described. This reaction provides an efficient approach to tertiary α‐hydroxycarbonyl ...compounds, which are highly valued chemicals and widely used in the chemical and pharmaceutical industry. The simple conditions and the use of molecular oxygen as both the oxidant and the oxygen source make this protocol very environmentally friendly and practical. This transformation is highly efficient and highly selective for tertiary C(sp3)H bond cleavage.
OH, so simple! A transition‐metal‐free Cs2CO3‐catalyzed α‐hydroxylation of carbonyl compounds with O2 provided a variety of tertiary α‐hydroxycarbonyl compounds (see scheme; DMSO=dimethyl sulfoxide), which are widely used in the chemical and pharmaceutical industry. The simple conditions and the use of molecular oxygen as both the oxidant and the oxygen source make this protocol very efficient and practical.
Ruthenium(IV) complexes were identified as key intermediates of C−H/O−H activations by weak O‐coordination. Thus, the annulations of sulfoxonium ylides by benzoic acids provided expedient access to ...diversely‐decorated isocoumarins with ample scope. Detailed experimental and computational studies provided strong support for a facile BIES‐C−H activation, along with cyclometalated ruthenium(IV) intermediates within a versatile ruthenium(II/IV) catalysis regime (BIES=base‐assisted internal electrophilic substitution).
RuIV for O: Versatile C−H/O−H functionalizations by weak O‐coordination were accomplished with sulfoxonium ylides through a ruthenium(II/IV) manifold.
C−H/C−C functionalizations with methylenecyclopropanes (MCPs) were accomplished with a versatile base‐metal catalyst. A robust manganese(I) complex enabled the expedient annulation of MCPs by ...synthetically meaningful ketimines to deliver, upon one‐pot hydroarylation, densely substituted polycylic anilines in a step‐economical fashion. Mechanistic studies provided strong support for a facile organometallic C−H manganation, while typical cobalt, ruthenium, rhodium, and palladium catalysts were found completely ineffective.
One stone, two birds: C−H/C−C activations were realized by a versatile MnI catalysis regime, thus enabling the stereoselective construction of polycyclic anilines. Mechanistic studies provided strong support for a facile C−H manganation while typical Co, Ru, Rh, and Pd catalysts were completely ineffective.
Expedient hydroarylations of C=Het bonds (Het=heteroatom) were accomplished by user‐friendly organometallic C−H activation in a positional‐selective manner. The broadly applicable C−H ...functionalization platform enabled the step‐economical transformation of aldehydes, ketones, and imines under additive‐free reaction conditions. In contrast to palladium, rhodium, ruthenium, rhenium, iridium, nickel, and cobalt catalysis, solely manganese(I) complexes outcompeted the innate substrate control, clearly highlighting the unique power of manganese(I) C−H activation catalysis.
One catalyst to rule them all: The unique selectivity of manganese(I) catalysis in heteroarene C−H activation set the stage for positional selective hydroarylations with ample scope under additive‐free conditions, outcompeting palladium, rhodium, ruthenium, rhenium, iridium, nickel, iron, and cobalt catalysts.
We have developed an unprecedented Pd‐catalyzed formal hydroalkylation of alkynes with hydrazones, which are generated in situ from naturally abundant aldehydes, as both alkylation reagents and ...hydrogen donors. The hydroalkylation proceeds with high regio‐ and stereoselectivity to form (Z)‐alkenes, which are more difficult to generate compared to (E)‐alkenes. The reaction is compatible with a wide range of functional groups, including hydroxy, ester, ketone, nitrile, boronic ester, amine, and halide groups. Furthermore, late‐stage modifications of natural products and pharmaceutical derivatives exemplify its unique chemoselectivity, regioselectivity, and synthetic applicability. Mechanistic studies indicate the possible involvement of Pd‐hydride intermediates.
In the (hydra)zone: A palladium‐catalyzed formal hydroalkylation of alkynes with hydrazones has been realized. The reaction proceeds with high regio‐ and stereoselectivity to form (Z)‐alkenes through a palladium‐hydride species.
Palladium-catalyzed regioselective di- or mono-arylation of
o
-carboranes was achieved using weakly coordinating amides at room temperature. Therefore, a series of B(3,4)-diarylated and ...B(3)-monoarylated
o
-carboranes anchored with valuable functional groups were accessed for the first time. This strategy provided an efficient approach for the selective activation of B(3,4)–H bonds for regioselective functionalizations of
o
-carboranes.
A nickel‐catalyzed reductive cross coupling reaction of carboxylic acids with disulfides is described. The readily available and inexpensive carboxylic acid is activated in situ by the formation of a ...mixed anhydride. The transformation occurs at room temperature with wide functional group tolerance to efficiently generate structurally diverse thioesters. Moreover, the reaction tolerated a broad substrate scope, including sterically hindered of disulfides. Ultimately, this powerful method could be applied to the late‐stage functionalization for the construction of diverse thioesters, affording a convenient and practical tactic to construct carbon‐sulfur bonds.
An unexpected metal-free CC triple bond cleavage, dioxygen activation, and reassembly into tryptophol derivatives has been developed. This chemistry provides a novel, simple, and efficient approach ...to highly valuable tryptophol derivatives from simple substrates under mild conditions. The mechanistic studies may promote the discovery of new methodologies through C–C bond cleavage and dioxygen activation.
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