Shan Tang

Nickel-Catalyzed Heck-Type Alkenylation of Secondary and Tertiary α-Carbonyl Alkyl Bromides†

the National Natural Science Foundation of China (20772093;20972118;20832003);the Fundamental Research Funds for the Central Universities, and the Program for New Century Excellent Talents in University and the Program for Changjiang Scholars and Innovative Research Team in University (IRT1030)

Transition-Metal-Assisted Radical/Radical Cross-Coupling: A New Strategy to the Oxidative C(sp3)–H/N–H Cross-Coupling

A transition-metal-assisted oxidative C(sp(3))-H/N-H cross-coupling reaction of N-alkoxyamides with aliphatic hydrocarbons is described. During the reaction, nitrogen radicals were generated from the oxidation of N-alkoxyamides. Experiments and DFT calculations revealed that transition-metal catalyst could lower the reactivity of the generated nitrogen radical by the coordination of the transition metal, which allowed the selective radical/radical cross-coupling with the transient sp(3) carbon radical to construct C(sp(3))--N bonds. Various C(sp(3))-H bonds could be transformed into C(sp(3))-N bonds through this radical amidation strategy.

Iodine-Catalyzed Radical Oxidative Annulation for the Construction of Dihydrofurans and Indolizines

Through iodine catalysis, the direct oxidative coupling/annulation of β-keto esters or 2-pyridinyl-β-esters with alkenes was achieved. This reaction procedure provides a simple and selective way for the synthesis of dihydrofurans and indolizines in one step.

Covalently Bound Benzyl Ligand Promotes Selective Palladium-Catalyzed Oxidative Esterification of Aldehydes with Alcohols†

the National Natural Science Foundation of China (21025206;20832003;20972118);the 973 Program (2012CB725302)

Electrocatalytic Oxidant-Free Dehydrogenative C−H/S−H Cross-Coupling

An environmentally friendly electrocatalytic protocol has been developed for dehydrogenative C-H/S-H cross-coupling. This method enabled C-S bond formation under catalyst- and oxidant-free conditions. Under undivided electrolysis conditions, various aryl/heteroaryl thiols and electron-rich arenes afforded the C-S bond-formation products in 24-99 % yield. A preliminary mechanistic study indicated that the generation of aryl radical cation intermediates is key to the success of this transformation.

Oxidant controlled Pd-catalysed selective oxidation of primary alcohols

The oxidant controlled palladium catalysed selective oxidation of primary alcohols to aldehydes or esters was investigated. The electronic properties of the benzylic alcohols and the structure of the oxidant are both important factors in controlling the selectivity between aldehydes and esters. A covalent benzyl ligand derived from BnCl provides η(3) coordination to the Pd centre. This covalent ligand is the key to the selective oxidative esterification of primary alcohols.

Carbon‐Centered Radical Addition to OC of Amides or Esters as a Route to CO Bond Formations

Among various types of radical reactions, the addition of carbon radicals to unsaturated bonds is a powerful tool for constructing new chemical bonds, in which the typical applied unsaturated substrates include alkenes, alkynes and imines. Carbonyl is perhaps the most common unsaturated group in nature. This work demonstrates a novel C-O bond formation through carbon-centered radical addition to the carbonyl oxygen of amide or ester, in which amide and ester groups are easily activated through the radical process. EPR spectroscopy and radical clock experiments support the radical process for this transformation, and density functional theory (DFT) calculations support the possibility of carbon-centered radical addition to the carbonyl oxygen of amides or esters.

Synergistic Pd/enamine catalysis: a strategy for the C-H/C-H oxidative coupling of allylarenes with unactivated ketones.

By combining catalytic nucleophilic enamine activation with Pd-catalyzed C-H activation of allylarenes, the first oxidative allylic alkylation of unactivated ketones was achieved. Mechanistically, the Pd-catalyzed allylic C-H activation and proline-catalyzed ketone nucleophilic activation worked synergistically for the oxidative cross-coupling between allylarenes and unactivated ketones.

Multimetallic catalysed radical oxidative C(sp(3))-H/C(sp)-H cross-coupling between unactivated alkanes and terminal alkynes.

Radical involved transformations are now considered as extremely important processes in modern organic synthetic chemistry. According to the demand by atom-economic and sustainable chemistry, direct C(sp3)–H functionalization through radical oxidative coupling represents an appealing strategy for C–C bond formations. However, the selectivity control of reactive radical intermediates is still a great challenge in these transformations. Here we show a selective radical oxidative C(sp3)–H/C(sp)–H cross-coupling of unactivated alkanes with terminal alkynes by using a combined Cu/Ni/Ag catalytic system. It provides a new way to access substituted alkynes from readily available materials. Preliminary mechanistic studies suggest that this reaction proceeds through a radical process and the C(sp3)–H bond cleavage is the rate-limiting step. This study may have significant implications for controlling selective C–C bond formation of reactive radical intermediates by using multimetallic catalytic systems.

Zinc‐Catalyzed Dehydrogenative Cross‐Coupling of Terminal Alkynes with Aldehydes: Access to Ynones

Because of the lack of redox ability, zinc has seldom been used as a catalyst in dehydrogenative cross-coupling reactions. Herein, a novel zinc-catalyzed dehydrogenative C(sp(2) )H/C(sp)H cross-coupling of terminal alkynes with aldehydes was developed, and provides a simple way to access ynones from readily available materials under mild reaction conditions. Good reaction selectivity can be achieved with a 1:1 ratio of terminal alkyne and aldehyde. Various terminal alkynes and aldehydes are suitable in this transformation.