Visible-Light-Mediated Anti-Markovnikov Hydration of Olefins

Considering that stoichiometric borane and oxidant are required in the classical alkene anti-Markovnikov hydration process, it remains appealing to achieve the transformation in a catalytic protocol. Herein, a visible-light-mediated anti-Markovnikov addition of water to alkenes by using an organic photoredox catalyst in conjunction with a redox-active hydrogen atom donor was developed, which avoided the need for a transition-metal catalyst, stoichiometric borane, as well as oxidant. Both terminal and internal olefins are readily accommodated in this transformation to obtain corresponding primary and secondary alcohols in good yields with single regioselectivity. This procedure can be scaled up to gram scale with a 230 turnover number based on photocatalyst

Trisulfur Radical Anion as the Key Intermediate for the Synthesis of Thiophene via the Interaction between Elemental Sulfur and NaO<i>t</i>Bu

A facile base-promoted sulfur-centered radical generation mode and a single-step protocol for the synthesis of thiophene derivatives using 1,3-diynes via the interaction between elemental sulfur and NaO<i>t</i>Bu has been reported. EPR experiments revealed that the trisulfur radical anion acts as a key intermediate of this process. A plausible mechanism has been proposed

Anti-Markovnikov Oxidation of β‑Alkyl Styrenes with H₂O as the Terminal Oxidant

Oxygenation of alkenes is one of the most straightforward routes for the construction of carbonyl compounds. Wacker oxidation provides a broadly useful strategy to convert the mineral oil into higher value-added carbonyl chemicals. However, the conventional Wacker chemistry remains problematic, such as the poor activity for internal alkenes, the lack of anti-Markovnikov regioselectivity, and the high cost and chemical waste resulted from noble metal catalysts and stoichiometric oxidant. Here, we describe an unprecedented dehydrogenative oxygenation of β-alkyl styrenes and their derivatives with water under external-oxidant-free conditions by utilizing the synergistic effect of photocatalysis and proton-reduction catalysis that can address these challenges. This dual catalytic system possesses the single anti-Markovnikov selectivity due to the property of the visible-light-induced alkene radical cation intermediate

Direct Observation of Reduction of Cu(II) to Cu(I) by Terminal Alkynes

X-ray absorption spectroscopy and <i>in situ</i> electron paramagnetic resonance evidence were provided for the reduction of Cu­(II) to Cu­(I) species by alkynes in the presence of tetramethylethylenediamine (TMEDA), in which TMEDA plays dual roles as both ligand and base. The structures of the starting Cu­(II) species and the obtained Cu­(I) species were determined as (TMEDA)­CuCl₂ and [(TMEDA)­CuCl]₂ dimer, respectively

Cobalt-Catalyzed Electrochemical Oxidative C–H/N–H Carbonylation with Hydrogen Evolution

Carbon monoxide is an abundant and cost-efficient C1 building block for the carbonylation industry. Transition-metal-catalyzed oxidative C–H/C­(X)–H carbonylation with CO provides one of the most straightforward approaches to construct carbonyl compounds. However, the use of stoichiometric oxidants would bring several drawbacks such as high cost and undesired chemical waste. Especially, the explosion limit is a potential safety hazard in oxidative carbonylation using O₂ as the oxidant. To overcome these issues, an electrochemical strategy for oxidative C–H/N–H carbonylation has been designed by taking advantage of anodic oxidation to recycle a cobalt catalyst, and H₂ is generated at the cathode. The intra- and intermolecular carbonylation products can be achieved with good functional group tolerance in 31%–99% yields. A plausible reaction mechanism involving a Co^II/Co^III/Co^I catalytic cycle is proposed by the studies of XANES and CV