C-H bond functionalization enables strategically new approaches to the synthesis of complex organic molecules including biologically active compounds, research probes and functional organic materials. To address the shortcomings of transition metal catalyzed processes, we have developed a new approach to direct coupling of sp(3) C-H bonds and alkenes based on Lewis acid-promoted hydride transfer. Activation of alpha,beta-unsaturated aldehydes and ketones with Lewis acid triggers intramolecular hydride transfer, leading to a zwitterionic intermediate, which in turn undergoes ionic cyclization to afford the cyclic alkylation product. The scope of this method is expanded by the generation of alkenyl-oxocarbenium species as highly activated alkene intermediates capable of abstracting a hydride from unreactive carbon centers, including benzyl-, allyl-, and crotyl-ethers, as well as primary alkyl ethers, at room temperature. The alkenyl acetal and ketal substrates show dramatically faster rates of cyclization, as well as improved chemical yield and diastereoselectivity, compared to the corresponding carbonyl compounds. Furthermore, the use of boron trifluoride etherate as the Lewis acid and ethylene glycol as the organocatalyst provides a highly active catalytic system, presumably via the in situ formation of alkenyl-oxocarbenium intermediates, which eliminates the need for expensive transition metal Lewis acids or the preparation of ketal substrates. This binary catalytic system greatly improves the efficiency of the hydride transfer-initiated alkylation reactions.
Download full-text PDF |
Source |
---|---|
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2954885 | PMC |
http://dx.doi.org/10.1021/ja806068h | DOI Listing |
Environ Sci Technol
January 2025
State Key Laboratory of Green Chemical Engineering and Industrial Catalysis, Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, PR China.
Catalytic elimination through an oxidative decomposition pathway is the most promising candidate for the purification of chlorinated volatile organic compound (CVOC) pollutants, but the complicated mechanisms and the formation pathways of hydrogenated byproducts still need to be clearly revealed. Herein, W/ZrO, as a structure-tunable catalyst, is used to catalytically oxidize dichloromethane (DCM) and clarify the formation pathway of monochloromethane (MCM). Crystal engineering of ZrO tailors surface WO species; practically, the predominant Zr-WO clusters and crystalline WO can be obtained on monoclinic (m-ZrO) and tetragonal (t-ZrO) phases.
View Article and Find Full Text PDFChem Commun (Camb)
January 2025
Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Korea.
1,4-Dihydronicotinamide adenine dinucleotide (NADH) and its phosphate ester (NADPH) are essential cofactors required for all living cells, playing pivotal roles in multiple biological processes such as energy metabolism and biosynthesis. NADPH is produced during photosynthesis by the combination of photosystem II, where water is oxidised, and photosystem I, where NADP is reduced. This review focuses on catalytic NAD(P) (and its analogues) reduction to generate 1,4-NAD(P)H without formation of other regioisomers and the dimer.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.
A series of Ni complexes bearing a redox and acid-base noninnocent tetraamido macrocyclic ligand, H-(TAML-4) {H-(TAML-4) = 15,15-dimethyl-5,8,13,17-tetrahydro-5,8,13,17-tetraaza-dibenzo[]cyclotridecene-6,7,14,16-tetraone}, with formal oxidation states of Ni, Ni, and Ni were synthesized and characterized structurally and spectroscopically. The X-ray crystallographic analysis of the Ni complexes revealed a square planar geometry, and the [Ni(TAML-4)] complex with the formal oxidation state of Ni was characterized to be [Ni(TAML-4)] with the oxidation state of the Ni ion and the one-electron oxidized TAML-4 ligand, TAML-4. The Ni oxidation state and the TAML-4 radical cation ligand, TAML-4, were supported by X-ray absorption spectroscopy and density functional theory calculations.
View Article and Find Full Text PDFChemistry
January 2025
TU Chemnitz: Technische Universitat Chemnitz, Insitut für Chemie, Straße der Nationen 62, 09111, Chemnitz, GERMANY.
The intramolecular migration of three hydrogen atoms from one moiety of a gaseous radical cation to the other prior to fragmentation is an extremely rare type of redox reaction. Within the scope of this investigation, this scenario requires an ionized but electron-rich arene acceptor bearing a para-(3-hydroxyalkyl) residue. The precise mechanism of such unidirectional 3H transfer processes, including the order of the individual H transfer steps, has remained unclear in spite of previous isotope labelling and recent infrared ion spectroscopy (IRIS) studies.
View Article and Find Full Text PDFJ Colloid Interface Sci
January 2025
State Key Laboratory of Silicon and Advanced Semiconductor Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou 310058, China. Electronic address:
The application and further industrialization of magnesium hydride (MgH) are restricted by its intrinsically high de-hydrogenation temperature and dragged kinetics though it is believed as one of the most encouraging solid-state hydrogen storage materials with considerable capacity. Herein, a bimetallic layered MXene VNbC, which was mixed with MgH by high energy ball milling, was obtained by etching compact layered MAX VNbAlC with HF. The beginning de-hydrogenation temperature of the as-prepared MgH blended with 10 wt% VNbC (denoted as MgH-10 VNbC) composites was excitingly 170 °C and it exhibited faster kinetics and excellent cycling stability.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!