Yuya Hu

Interfacial sites play critical roles in catalysis. However, the nature of the active interfacial sites for the photoelectroreduction of CO₂ is not well understood. In their Communication on https://doi.org/10.1002/anie.201805256page 15415 ff., J. Gong and co‐workers describe the deposition of metallic Cu nanoparticles on Cu₂O films and their interactions, as well as the dependence of the CO₂ reduction pathway on the Cu/Cu₂O interface. The carefully designed Cu/Cu₂O interfaces balance the binding strengths of the H* and CO* intermediates, which enables efficient methanol production.

No longer flat: A cis‐selective hydrogenation of abundant aryl boronic acids and their derivatives catalyzed by Rh–CAAC is reported. The reaction tolerates a variety of boron‐protecting groups and provides direct access to a broad range of saturated borylated carbo‐ and heterocycles with various functional groups. The utility of these saturated cyclic building blocks was demonstrated by post‐functionalization of the boron group.

Abstract

A cis‐selective hydrogenation of abundant aryl boronic acids and their derivatives catalyzed by rhodium cyclic (alkyl)(amino)carbene (Rh–CAAC) is reported. The reaction tolerates a variety of boron‐protecting groups and provides direct access to a broad scope of saturated, borylated carbo‐ and heterocycles with various functional groups. The transformation is strategically important because the versatile saturated boronate products are difficult to prepare by other methods. The utility of the saturated cyclic building blocks was demonstrated by post‐functionalization of the boron group.

Deconstructive diversification of cyclic amines

Deconstructive diversification of cyclic amines, Published online: 31 October 2018; doi:10.1038/s41586-018-0700-3

Abstract

By modification of pore size and morphology, pore‐expanded variants of SBA‐15 and KIT‐6 have been utilised as mesoporous silica supports for the immobilisation of a bimetallic aluminium‐salen complex. The performance of the resulting heterogeneous catalysts in the synthesis of cyclic carbonates from carbon dioxide and terminal epoxides was assessed. Support materials which retained higher pore volume and surface areas after catalyst immobilisation demonstrated enhanced conversions to the desired cyclic carbonates. This was rationalised to be a consequence of the promotion of reactant mass transport through a less‐inhibited pore structure.

Metallic copper nanoparticles were deposited on Cu₂O films to change the product distribution of CO₂ reduction in aqueous solution from the gaseous products generated on bare Cu₂O to predominantly methanol. The carefully designed Cu/Cu₂O interfaces balance the binding strengths of the H* and CO* intermediates, which enables efficient methanol production.

Abstract

Artificial photosynthesis can be used to store solar energy and reduce CO₂ into fuels to potentially alleviate global warming and the energy crisis. Compared to the generation of gaseous products, it remains a great challenge to tune the product distribution of artificial photosynthesis to liquid fuels, such as CH₃OH, which are suitable for storage and transport. Herein, we describe the introduction of metallic Cu nanoparticles (NPs) on Cu₂O films to change the product distribution from gaseous products on bare Cu₂O to predominantly CH₃OH by CO₂ reduction in aqueous solutions. The specifically designed Cu/Cu₂O interfaces balance the binding strengths of H* and CO* intermediates, which play critical roles in CH₃OH production. With a TiO₂ model photoanode to construct a photoelectrochemical cell, a Cu/Cu₂O dark cathode exhibited a Faradaic efficiency of up to 53.6 % for CH₃OH production. This work demonstrates the feasibility and mechanism of interface engineering to enhance the CH₃OH production from CO₂ reduction in aqueous electrolytes.

Drink of water: A general, practical, and scalable means of preparing deuterated aldehydes from aromatic and aliphatic carboxylic acids has been developed with D₂O as an inexpensive deuterium source (see scheme). The transformation, enabled by synergistic photoredox catalysis, thiol catalysis, and phosphoranyl radical chemistry, shows broad scope and good functional‐group tolerance and can be used for late‐stage deoxygenative deuteration.

Abstract

We report a general, practical, and scalable means of preparing deuterated aldehydes from aromatic and aliphatic carboxylic acids with D₂O as an inexpensive deuterium source. The use of Ph₃P as an O‐atom transfer reagent can facilitate the deoxygenation of aromatic acids, while Ph₂POEt is a better O‐atom transfer reagent for aliphatic acids. The highly precise deoxygenation of complex carboxylic acids makes this protocol promising for late‐stage deoxygenative deuteration of natural product derivatives and pharmaceutical compounds.

In sync with zinc: A dinuclear heterometallic CoZn catalyst shows much higher photocatalytic activity than the corresponding dinuclear homometallic CoCo and ZnZn catalysts, or the mononuclear Co and Zn catalysts for CO₂ reduction under the same conditions. The high performance of the CoZn catalyst is due to the enhanced dinuclear metal synergistic catalysis (DMSC) effect between Zn^II and Co^II.

Abstract

The solar‐driven CO₂ reduction is a challenge in the field of “artificial photosynthesis”, as most catalysts display low activity and selectivity for CO₂ reduction in water‐containing reaction systems as a result of competitive proton reduction. Herein, we report a dinuclear heterometallic complex, [CoZn(OH)L¹](ClO₄)₃ (CoZn), which shows extremely high photocatalytic activity and selectivity for CO₂ reduction in water/acetonitrile solution. It achieves a selectivity of 98 % for CO₂‐to‐CO conversion, with TON and TOF values of 65000 and 1.8 s⁻¹, respectively, 4, 19, and 45‐fold higher than the values of corresponding dinuclear homometallic [CoCo(OH)L¹](ClO₄)₃ (CoCo), [ZnZn(OH)L¹](ClO₄)₃ (ZnZn), and mononuclear [CoL²(CH₃CN)](ClO₄)₂ (Co), respectively, under the same conditions. The increased photocatalytic performance of CoZn is due to the enhanced dinuclear metal synergistic catalysis (DMSC) effect between Zn^II and Co^II, which dramatically lowers the activation barriers of both transition states of CO₂ reduction.

A cooperative catalytic method for the asymmetric oxa‐Pictet–Spengler reaction has been developed. This method, demonstrated in the synthesis of substituted tetrahydropyranoindoles, has enabled a six‐step asymmetric synthesis of (−)‐coixspirolactam C.

Abstract

Carbocations stabilized by adjacent oxygen atoms are useful reactive intermediates involved in fundamental chemical transformations. These oxocarbenium ions typically lack sufficient electron density to engage established chiral Brønsted or Lewis acid catalysts, presenting a major challenge to their widespread application in asymmetric catalysis. Leading methods for selectivity operate primarily through electrostatic pairing between the oxocarbenium ion and a chiral counterion. A general approach to new enantioselective transformations of oxocarbenium ions requires novel strategies that address the weak binding capabilities of these intermediates. We demonstrate herein a novel cooperative catalysis system for selective reactions with oxocarbenium ions. This new strategy has been applied to a highly selective and rapid oxa‐Pictet–Spengler reaction and highlights a powerful combination of an achiral hydrogen bond donor with a chiral Brønsted acid.

Abstract

The development of hydrogen bond donors (HBDs) as catalytic moieties in the cycloaddition of carbon dioxide to epoxides is an active field of research to access efficient, inexpensive and sustainable metal‐free systems for the conversion of carbon dioxide to useful chemicals. Thus far, no systematic attempt to correlate the activity of a diverse selection of HBDs to their physico‐chemical properties has been undertaken. In this work, we investigate factors influencing the catalytic activity of hydroxyl HBDs from different chemical families under ambient conditions by considering the HBDs Brønsted acidity (expressed as pK_a), the number of hydroxyls and structural aspects. As an effect, this study highlights the crucial role of the hydroxyl protons’ Brønsted acidity in determining the catalytic activity of the HBDs, identifies an ideal range for the hydroxyl HBDs proton acidity (9 <pK_a <11) and leads to a revaluation of phenol and to the discovery of a simple ascorbic acid derivative as efficient HBDs for the title cycloaddition reaction. Density functional theory (DFT) calculations show mild reactions barriers for the reaction catalysed by phenol and suggest the occurrence of aggregation between molecules of ascorbic acid as a further factor affecting catalytic activity.

Coming to light: Report herein is a highly regioselective, intermolecular, nickel‐catalyzed photoredox allylic substitution that expands both the radical and electrophile scope of dual photoredox/Ni‐catalyzed reactions. Quantum mechanical calculations shed light on the mechanistic pathway, supporting a Ni⁰ to Ni^II oxidative addition followed by an inner‐sphere radical addition. PC=photocatalyst, RP=radical precursor.

Abstract

A regioselective, nickel‐catalyzed photoredox allylation of secondary, benzyl, and α‐alkoxy radical precursors is disclosed. Through this manifold, a variety of linear allylic alcohols and allylated monosaccharides are accessible in high yields under mild reaction conditions. Quantum mechanical calculations [DFT and DLPNO‐CCSD(T)] support the mechanistic hypothesis of a Ni⁰ to Ni^II oxidative addition pathway followed by radical addition and inner‐sphere allylation.

Two in one sweep: A doubly reduced 9,10‐diboraanthracene splits CO₂ quantitatively and under ambient conditions to give CO and carbonate ions. If lithium metal is used as the reducing agent, Li₂CO₃ precipitates from the reaction mixture and the CO₂ reduction process becomes catalytic.

Abstract

Alkali metal salts M₂[1] (M=Li, Na) of doubly reduced 9,10‐dimethyl‐9,10‐dihydro‐9,10‐diboraanthracene (1) instantaneously add the C=O bond of CO₂ across their boron centers to furnish formal [4+2]‐cycloadducts M₂[2]. If only 1 equiv of CO₂ is supplied, these products are stable. In the presence of excess CO₂, however, C−O bond cleavage occurs and an O²⁻ equivalent is transferred to CO₂ to furnish CO and [CO₃]²⁻. With M=Li, Li₂CO₃ precipitates and the neutral 1 is liberated such that it can be reduced again to establish a catalytic cycle. With M=Na, [CO₃]²⁻ remains coordinated to both boron atoms in a bridging mode (Na₂[4]). A mechanistic scenario is proposed, based on isolated intermediates and model reactions.

Iron out: A method for vinyl carbenoid transfer using sulfoxonium ylides is reported. In situ generation of a sulfoxonium ylide, an iron carbenoid, and nitrogen ylide, with subsequent (3+2) annulation in a one‐pot process leads to indolizines. This reaction demonstrates the efficiency of the method for vinyl‐carbenoid‐mediated transformations.

Abstract

A method for the generation of unprecedented vinyl carbenoids from sulfoxonium ylides has been developed and applied in the synthesis of a diverse array of heterocycles such as indolizines, pyrroles, 3‐pyrrolin‐2‐ones, and furans. The reactions proceed by FeBr₂ catalysis under mild reaction conditions with a broad substrate scope. A reaction pathway involving iron carbenoids is proposed based on a series of control experiments and DFT calculations.