Sustainable System for Hydrogenation Exploiting Energy Derived from Solar Light

Electricity-driven organic hydrogenation using water as the hydrogen source

Hydrogenation is a pivotal process in organic synthesis and various catalytic strategies have been developed in achieving effective hydrogenation of diverse substrates. Despite the competence of these methods, the predominant reliance on molecular hydrogen (H2) gas under high temperature and elevated pressure presents operational challenges. Other alternative hydrogen sources such as inorganic hydrides and organic acids are often prohibitively expensive, limiting their practical utility on a large scale. In contrast, employing water as a hydrogen source for organic hydrogenation presents an attractive and sustainable alternative, promising to overcome the drawbacks associated with traditional hydrogen sources. Integrated with electricity as the sole driving force under ambient conditions, hydrogenation using water as the sole hydrogen source aligns well with the environmental sustainability goals but also offers a safer and potentially more cost-effective solution. This article starts with the discussion on the inherent advantages and limitations of conventional hydrogen sources compared to water in hydrogenation reactions, followed by the introduction of representative electrocatalytic systems that successfully utilize water as the hydrogen source in realizing a large number of organic hydrogenation transformations, with a focus on heterogeneous electrocatalysts. In summary, transitioning to water as a hydrogen source in organic hydrogenation represents a promising direction for sustainable chemistry. In particular, by exploring and optimizing electrocatalytic hydrogenation systems, the chemical industry can reduce its reliance on hazardous and expensive hydrogen sources, paving the way for safer, greener, and less energy-intensive hydrogenation processes.

Catalyst-Free Transfer Hydrogenation of Activated Alkenes Exploiting Isopropanol as the Sole and Traceless Reductant

Both metal-catalyzed and organocatalytic transfer hydrogenation reactions are widely employed for the reduction of C=O and C=N bonds. However, selective transfer hydrogenation reactions of C=C bonds remain challenging. Therefore, the chemoselective transfer hydrogenation of olefins under mild conditions and in the absence of metal catalysts, using readily available and inexpensive reducing agents (i.e. primary and secondary alcohols), will mark a significant advancement towards the development of green transfer hydrogenation strategies. Described herein is an unconventional catalyst-free transfer hydrogenation reaction of activated alkenes using isopropanol as an eco-friendly reductant and solvent. The reaction gives convenient synthetic access to a wide range of substituted malonic acid half oxyesters (SMAHOs) in moderate to good yields. Mechanistic investigations point towards an unprecedented hydrogen bond-assisted transfer hydrogenation process.

Elevating the Photothermal Conversion Efficiency of Phase-Change Materials Simultaneously toward Solar Energy Storage, Self-Healing, and Recyclability

To alleviate the predicament of resource shortage and environmental pollution, efficiently using abundant solar energy is a great challenge. Herein, we prepared unique photothermal conversion phase-change materials, namely, CNT@PCMs, by introducing carbon nanotubes (CNTs) used as photothermal conversion materials into the recyclable matrix of phase-change materials (PCMs). These devised CNT@PCMs cleverly combine the photothermal conversion capability of CNTs and the thermal energy storage capability of traditional PCMs. Especially, the surface temperature of the prepared CNT@PCMs can be raised to 100 °C within 165 s under the solar simulator (150 mW cm^-2), showing a surprising heating rate that is much higher than that of the reported works and achieving a higher photothermal conversion efficiency for solar energy in this work. Furthermore, these CNT@PCMs can hold high melting latent heat with a maximum value at 110.0 J g^-1, exhibiting remarkable thermal storage ability aside from preeminent photothermal conversion capability. Intriguingly, the introduction of dynamic oxime group-carbamate bonds into the molecular structure can endow CNT@PCMs with an outstanding self-healing performance and recyclability. The broken CNT@PCMs sample can be healed in 2 min under IR-laser irradiation. Importantly, the phase-change and mechanical properties and photothermal conversion efficiency of CNT@PCMs can also remain virtually unchanged after multiple recycles. It is of great significance to design this style of CNT@PCMs for achieving the efficient utilization of solar energy and environmental protection.

Transfer hydrogenation of pyridinium and quinolinium species using ethanol as a hydrogen source to access saturated N-heterocycles

Catalytic transfer hydrogenation (TH) for the reduction of heterocycles is an emerging strategy for accessing biologically active saturated N-heterocycles. Herein, we report a TH protocol that utilizes ethanol as a...

Selective Buchwald–Hartwig arylation of C-amino-1,2,4-triazoles and other coordinating aminoheterocycles enabled by bulky NHC ligands and TPEDO activator

A facile method for selective N-(hetero)arylation of coordinating 3(5)-amino-1,2,4-triazoles under Pd/NHC catalysis using TPEDO as a new efficient Pd(ii) to Pd(0) reductant has been developed.

Visible Light-Driven and Singlet Oxygen-Mediated Photochemical Cross-Dehydrogenative C3-H Sulfenylation of 4-Hydroxycoumarins with Thiols Using Rose Bengal as a Photosensitizer

A visible light (white light-emitting diode/direct sunlight)-driven photochemical synthesis of a new series of biologically interesting 3-(alkyl/benzylthio)-4-hydroxy-2H-chromen-2-ones has been achieved through a cross-dehydrogenative C₃-H sulfenylation of 4-hydroxycoumarins with thiols at ambient temperature in the presence of rose bengal in acetonitrile under an oxygen atmosphere. The notable features of this newly developed method are mild reaction conditions, energy efficiency, metal-free synthesis, good to excellent yields, use of low-cost materials, and eco-friendliness.