Copper‐catalyzed aerobic coupling of thiols and alcohols affords sulfinates and thiosulfonates. These products are assumed to form via sulfinyl radicals which are not commonly found in oxidative coupling reactions of thiols. A reaction mechanism involving sulfinyl radicals is proposed, and mass and electron paramagnetic resonance (EPR) experimental results are provided.
The palladium‐catalyzed ketone‐directed dual sp2 C H activation and sp3 C H functionalization has been applied for fullerene functionalization for the first time. The sec‐alkyl aryl ketones have been exploited to react with [60]fullerene (C60) to provide the novel and scarce C60‐fused tetralones. The combined use of a highly active cationic palladium(II) catalyst and trifluoromethanesulfonic acid is crucial for the improvement of the reaction yield. A plausible reaction mechanism leading to the observed products has been proposed, and the electrochemistry of the fullerene products has also been investigated.
A metal‐free aerobic autoxidative nitrooxylation of alkenyl oximes mediated by tert‐butyl nitrite is described. Molecular oxygen is used as the oxidizing reagent, avoiding use of organic trapping reagents such as 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO). The desired products were obtained in generally high yields.
An intramolecular palladium(II)‐catalyzed dearomative arylation reaction of indoles via C H bond functionalization was developed, providing access to structurally novel spiroindolenines with moderate to good yields. A one‐pot process for the synthesis of spiroindoline derivatives was also realized.
A new visible light‐initiated 1,5‐hydride radical shift strategy has been developed to enable the one‐step functionalization of both a C(sp3) Br bond and a C(sp3) H bond adjacent to the same carbon atom. This visible light photoredox catalysis offers a mild and straightforward access to diverse five‐membered carbocyclic ring‐fused polycyclic hydrocarbons with high turnover numbers (TONs; up to 4.93×103) and broad substrate scope.
With molybdenum hexacarbonyl as the carbon monoxide source, a general palladium‐catalyzed carbonylative transformation of the C−H bond on aromatic rings to produce esters has been developed. Good yields of the corresponding products have been obtained with wide functional group tolerance and excellent regioselectivity. A variety of aliphatic alcohols are suitable reactants here.
A series of geometry‐constrained iminopyridyl‐palladium chlorides were synthesized and characterized. These phosphine‐free palladium complexes were explored for their catalytic activities in both Suzuki and Heck cross‐coupling reactions, achieving turnover numbers as high as 106 towards various aryl bromides, even those containing various functionalities. In addition, the influence of substituents with steric and electronic factors was reflected by the differences observed in their activities.
An enantioselective one‐pot Michael/Michael/Henry/hemiacetalization reaction between α,β‐unsaturated aldehydes, α‐ketoamides, and nitroalkenes under mild conditions catalyzed by a diarylprolinol silyl ether has been developed. The sequential methodology provides a direct approach to a wide range of fully substituted chiral oxabicyclo[2.2.2]octanes with seven contiguous stereocenters in moderate to excellent yields (up to 99%), high to excellent diastereoselectivities (up to >25:1 dr), and high to excellent enantioselectivities (up to 99% ee).
The first catalytic asymmetric construction of the cyclic enaminone‐based 3‐substituted 3‐amino‐2‐oxindole scaffold with potential bioactivity has been developed via chiral phosphoric acid‐catalyzed enantioselective addition reactions of cyclic enaminones to isatin‐derived imines, which afforded a series of cyclic enaminone‐based 3‐substituted 3‐amino‐2‐oxindoles in high yields and excellent enantioselectivities (up to 99% yield, 97% ee). The investigation of the reaction mechanism suggested that it was facilitated by a dual hydrogen‐bonding activation mode between the two substrates and the chiral phosphoric acid. Besides, this method could be utilized for a large‐scale synthesis with maintained enantioselectivity. This approach will not only offer a useful method for enantioselective construction of the cyclic enaminone‐based 3‐substituted 3‐amino‐2‐oxindole scaffold, but also enrich the research on catalytic asymmetric addition reactions of isatin‐derived imines by using electron‐rich olefins as nucleophiles. More importantly, a preliminary evaluation on the cytotoxicity of some selected products revealed that two of the enantio‐pure compounds exhibited moderate to strong cytotoxicity to A549, 786‐0, ECA109 and BT474 cancer cell lines.
Herein we describe a new methodology for the asymmetric hydrogenation (AH) of 2‐substituted pyridinium salts. An iridium catalyst based on a mixture of a chiral monodentate phosphoramidite and an achiral phosphine was shown to hydrogenate N‐benzyl‐2‐arylpyiridinium bromides to the corresponding N‐benzyl‐2‐arylpiperidines with full conversion and good enantioselectivity. The mechanism of the reaction under optimized conditions was investigated via kinetic measurements and isotopic labeling experiments. Our study suggests that the hydrogenation starts with a 1,4‐hydride addition and that the enantiodiscriminating step involves the reduction of an iminium intermediate.
