Zhiliang Huang

Iron-Catalyzed Oxidative Radical Cross-Coupling/Cyclization between Phenols and Olefins†

Iron-Catalyzed Oxidative Radical CrossCoupling/Cyclization between Phenols and Olefins Selectively free : A highly efficient and selective iron-catalyzed oxidative radical cross-coupling/cyclization to prepare dihydrobenzofurans under mild conditions had been established. Phenols and olefins are directly utilized as clean nucleophiles. Mechanistic investigations revealed that the reaction proceeds through a radical pathway, and the high selectivity is due to the Lewis acid. Angewandte Chemie

Cu(II)-Cu(I) synergistic cooperation to lead the alkyne C-H activation.

An efficient alkyne C-H activation and homocoupling procedure has been studied which indicates that a Cu(II)/Cu(I) synergistic cooperation might be involved. In situ Raman spectroscopy was employed to study kinetic behavior, drawing the conclusion that Cu(I) rather than Cu(II) participates in the rate-determining step. IR, EPR, and X-ray absorption spectroscopy evidence were provided for structural information, indicating that Cu(I) has a stronger interaction with alkyne than Cu(II) in the C-H activation step. Kinetics study showed Cu(II) plays a role as oxidant in C-C bond construction step, which was a fast step in the reaction. X-band EPR spectroscopy showed that the coordination environment of CuCl2(TMEDA) was affected by Cu(I). A putative mechanism with Cu(I)-Cu(II) synergistic cooperation procedure is proposed for the reaction.

Radical–Radical Cross-Coupling for C–S Bond Formation

A new method was demonstrated to overcome the selectivity issue of radical-radical cross-coupling toward the synthesis of asymmetric diaryl thioethers. The preliminary mechanism was revealed by radical-trapping experiments, DFT calculations, and kinetics, etc., indicating that the C-S bond formed through cross-coupling of a thiyl radical and an aryl radical cation. Moreover, the formation of an aryl radical cation instead of the C-H bond cleavage was determined as the rate-limiting step.

Transmetalation is the Rate-Limiting Step: Quantitative Kinetic Investigation of Nickel-Catalyzed Oxidative Coupling of Arylzinc Reagents

Transmetalation is the rate-limiting step! The transmetalation between arylzinc reagents and ArNi(II)R was confirmed as the rate-limiting step in the nickel-catalyzed oxidative coupling reactions. It was proved to be an excellent model allowing the first quantitative measurement of the kinetic rate constants of transmetalation from a live catalytic system. Rate constants from 0.04 to 0.31 M(-1) s(-1) were obtained for different arylzinc reagents under the conditions, and the activation enthalpy DeltaH(++) was 14.6 kcal/mol for PhZnCl. The substituent effect on the transmetalation was also gained for the first time from the catalytic reaction.

Symbiotic Catalysis Relay: Molecular Oxygen Activation Catalyzed by Multiple Small Molecules at Ambient Temperature and its Mechanism

the National Natural Science Foundations of China (20772111;20876149;21025206;20832003;20972118;20772093);the “973” Project from the MOST of China (2011CB808600);“the Fundamental Research Funds for the Central Universities”;the Program for New Century Excellent Talents in University (NCET);the Academic Award for Excellent Ph.D. Candidates funded by Ministry of Education of China

Nickel-Catalyzed Oxidative C-H/N-H Isocyanide Insertion: An Efficient Synthesis of Iminoisoindolinone Derivatives.

Transition metal-catalyzed isocyanide insertion has served as a fundamental and important chemical transformation. Classical isocyanide insertion usually occurs between organohalides and nucleophiles, which normally involves tedious and non-atom-economical prefunctionalization processes. However, oxidative C-H/N-H isocyanide insertion offers an efficient and green alternative. Herein, a nickel-catayzed oxidative C-H/N-H isocyanide insertion of aminoquinoline benzamides has been developed. Different kinds of iminoisoindolinone derivatives could be synthesized in good yields by utilizing Ni(acac)2 as the catalyst. In this transformation, isocyanide serves as an efficient C1 connector, which further inserted into two simple nucleophiles (C-H/N-H), representing an effective way to construct heterocycles.

para-Selective C–H bond functionalization of iodobenzenes

Selective C-H bond activation and functionalization is an invaluable and eco-friendly tool for new chemical bond construction. Recently, great progress has been made in the highly selective ortho- and meta-C-H bond functionalization of arene derivatives. In contrast, the remote para-C-H bond functionalization still remains a challenge. Herein, an oxidation-induced strategy for para-selective C-H bond functionalization of iodobenzenes towards the synthesis of various useful asymmetric diaryl ethers was demonstrated. This strategy not only provides a novel method for para-C-H bond functionalization, but also proposes a general idea for the development of new, highly selective para-C-H functionalization reactions.

Copper-catalyzed aerobic oxidative coupling: From ketone and diamine to pyrazine.

A new copper-catalyzed reaction toward the synthesis of pyrazine compounds is demonstrated. Copper-catalyzed aerobic oxidative C–H/N–H coupling between simple ketones and diamines was developed toward the synthesis of a variety of pyrazines. Various substituted ketones were compatible for this transformation. Preliminary mechanistic investigations indicated that radical species were involved. X-ray absorption fine structure experiments elucidated that the Cu(II) species 5 coordinated by two N atoms at a distance of 2.04 Å and two O atoms at a shorter distance of 1.98 Å was a reactive one for this aerobic oxidative coupling reaction. Density functional theory calculations suggested that the intramolecular coupling of cationic radicals was favorable in this transformation.

Copper-catalyzed and iodide-promoted aerobic C–C bond cleavage/C–N bond formation toward the synthesis of amides

A copper-catalyzed and iodide-promoted aerobic C–C bond cleavage/C–N bond formation reaction between ketone and simple amine was developed toward the synthesis of amides, which are useful synthetic intermediates in organic synthesis and important skeletons of biologically active molecules. Notably, the reaction conditions are very mild, and preliminary mechanistic investigations indicate that molecular oxygen might be involved in the C–C bond cleavage process.

Aromatic C–H bond cleavage by using a Cu(I) ate-complex

In situ X-ray absorption spectroscopy (XAS), infrared (IR) and nuclear magnetic resonance (NMR) techniques were used to identify the structures and reactivity of copper-containing active intermediates in the sp2 C–H bond cleavage reaction of electron-deficient aromatics. An ate-complex [Cu(OtBu)2]Na was found to be able to cleave the C–H bond of benzothiazole (ArH) producing [ArCuI(OtBu)]Na with a rate constant of 3.2 × 10−2 mol−1 L s−1 at −50 °C and with an activation enthalpy of 0.73 kcal mol−1 at room temperature.