Latest ArticlesReliable technologies for CO2 capture and conversion (C3) are of vital importance for the establishment of a sustainable society. Metal-organic framework (MOF) composites have shown their compelling potentials for C3 due to the plentiful reticular chemistry of MOF structures and the synergistic catalysis between MOFs and the functional guests. This review focuses on the syntheses and catalytic applications towards C3 of MOF composites, which is divided into three sections. The first section gives a brief introduction about synthetic strategies of MOF composites. The second section discusses the recent progress of MOF composites in C3, including CO2 chemical fixation, hydrogenation, photoreduction, electroreduction and photoelectroreduction. The third section summarizes the challenges and future prospects of MOF composites for C3. We hope that this review cannot only provide an inspiration for the rational design of MOF composites for C3, but also stimulate more and more research works in this emerging area.
The N-heterocyclic carbene (NHC)-catalyzed reactions involving two-electron reaction pathway have been well-established. However, the development of NHC-catalyzed radical reactions is still in its infancy in terms of reaction types and enantioselectivity. In the past decade, several elegant NHC-catalyzed radical reactions have been developed, including NHC-catalyzed oxidation of aldehydes to esters, reductive coupling reactions using Breslow intermediate as SET reductant and NHC-catalyzed reactions via radical homoenolates, dienoaltes and trienolates. This review summarizes the recent advances in NHC-catalyzed reactions involving radical intermediates.
Atkamine is a complex marine pyrroloiminoquinone alkaloid that comprises a heptacyclic scaffold bearing five different heterocycles and four contiguous stereocenters, and therefore it is a highly challenging target for synthetic chemists. We herein reported a modular synthetic strategy toward this alkaloid, featuring a formal [5 + 2] annulation and an asymmetric Michael addition. The efficient synthesis of the long-chain aliphatic aldehyde and chiral amino acetal fragments have been achieved. A simplified tetracyclic intermediate bearing the core structure of atkamine has been successfully constructed through the formal [5 + 2] annulation.
An unprecedented chiral secondary amine-catalyzed [3 + 3] annulation of isatin N,N'-cyclic azomethine imines with α,β-unsaturated aldehydes was developed. This strategy allowed the construction of structurally novel spiro N-heterocyclic oxindole derivatives in good yields (up to 91%) and good to excellent enantioselectivities (up to >99% ee), albeit with modest diastereoselectivities (up to 3.1:1 dr).
Monodispersed palladium phosphide (Pd3P) (5.2 ±0.5 nm) was firstly applied to photocatalytic Suzuki coupling reaction under visible light irradiation with CdS nanoflake as a photosensitizer. This heterogeneous system exhibited high yields to corresponding products and excellent stability in alcohol solvent at room temperature.
Metal-free anti-Markovnikov hydroalkylation of unactivated alkenes with cyanoacetate has been developed, featuring the use of a dual-component initiator containing an organic photocatalyst and a radical precursor. When combined, the two components can undergo visible light-induced single-electron transfer, and serve as a versatile and effective alkyl radical generator.
An efficient, sustainable and scalable strategy for the synthesis of porous cobalt/nitrogen co-doped carbons (Co@NCs) via pyrolysis of aniline-modified ZIFs, has been demonstrated. Aniline can coordinate and absorb on the surface of ZIF (ZIF-CoZn3-PhA), accelerate the precipitation of ZIFs, thus resulting in smaller ZIF particle size. Meanwhile, the aniline on the surface of ZIF-CoZn3-PhA promotes the formation of the protective carbon shell and smaller Co nanoparticles, and increases nitrogen content of the catalyst. Because of these properties of Co@NC-PhA-3, the oxidative esterification of 5-hydroxyme-thylfurfural can be carried out under ambient conditions. According to our experimental and computational results, a synergistic catalytic effect between CoNx sites and Co nanoparticles has been established, in which both Co nanoparticles and CoNx can activate O2 while Co nanoparticles bind and oxidize HMF. Moreover, the formation and release of active oxygen species in CoNx sites are reinforced by the electronic interaction between Co nanoparticles and CoNx.
Transition metal-catalyzed carbene transfer reaction is one of the most notable advances for C−C bond formation reactionsduring the past decade, which has been widely employed in the preparation of C3-substituted indoles. Here, we described an efficient example of catalyst- and metal-free aminoboration of alkynes and C−C bond formation with diazo compounds to produce C3-substituted indoles. Diverse alkynylanilines and diazo compounds can be utilized for this tandem transformation under mild reaction conditions, resulting in broad functional group compatibility. Additionally, this metal-free strategy can be extended to construct substituted benzofurans.
Acid-controlled, chemodivergent and redox-neutral annulations for the synthesis of isocoumarins and isoquinolinones have been realized via Rh(III)-catalyzed C—H activation. Diazo compounds act as a carbene precursor, and coupling occurs in one-pot process, where adipic acid and trimethylacetic acid promote chemodivergent cyclizations.
Chemoselective amine bioconjugation has long been a challenge for native protein modification. Inspired by Thiele's seminal discovery, Li and co-workers recently developed an ortho-phthalaldehyde (OPA) based reagent for labeling the amino group of a protein. Here we report an expeditious and scalable synthesis of a Li—Thiele reagent featuring an arene construction strategy. The reagent contains an alkyne side chain as a handle for secondary modification.