Highly selective conjugate additions of Grignard reagents to cyclic and linear enones catalyzed by recyclable heterogeneous polysaccharide/nanocopper catalysts are disclosed. The method also allows the synthesis of ketones with an all‐carbon quaternary center. When integrated with catalytic asymmetric tandem reactions using enals and β‐ketoesters, it yields chiral β,δ‐disubstituted ketones with high stereoselectivity.

Nature efficiently produces a myriad of structurally diverse carbon ring frameworks from common linear precursors via cyclization reactions at specific olefinic sites in dienes or polyenes. In contrast, achieving the site-selective functionalization of diene or polyene substrates remains a formidable challenge in chemical synthesis. Herein, we report a pair of highly site-selective, regiodivergent carbocyclization reactions of dienallenes and trienallenes, enabling the efficient synthesis of cis-1,4-disubstituted cyclohexenes and trans-1,2-disubstituted cyclobutenes from a common precursor with high diastereoselectivity. Remarkably, simple achiral organophosphoric acids and amines are identified as powerful ligands for controlling these palladium-catalyzed regiodivergent carbocyclizations. This approach represents the first example of site-selective regiodivergent carbocyclization, providing a practical method for the stereospecific synthesis of thermodynamically disfavored cis-1,4-disubstituted cyclohexenes and fully substituted trans-1,2-cyclobutenes. Additionally, the methodology developed offers general insights into the development of metal-catalyzed site-selective, regiodivergent carbocyclizations of diene and polyene precursors, mimicking natural carbocyclization processes.

image [ 104439‐77‐2 ] C 62 H 42 O 6 Ru 2 (MW 1085.13) InChI = 1S/2C29H21O.4CO.2Ru/c2*30‐29‐27(23‐17‐9‐3‐10‐18‐23)25(21‐13‐5‐1‐6‐14‐21)26(22‐15‐7‐2‐8‐16‐22)28(29)24‐19‐11‐4‐12‐20‐24;4*1‐2;;/h2*1‐20,30H;;;;;; InChIKey = CJXMWRIOTYFOAD‐UHFFFAOYSA‐N (oxidation, reduction, racemization, dynamic kinetic resolution, dynamic kinetic asymmetric transfermation) Alternative Name: Shvo's catalyst. Physical Data: melting point 223–227 °C. Solubility: most polar solvents (toluene, CH 2 Cl 2 , THF, 2‐propanol); reacts with alcohols. Formed Supplied in: light orange crystalline solid. Analysis of Reagent Purity: 1 H NMR. Integrate the bridging hydride to the aromatic region (40:1). Preparative Methods: recrystallized from CH 2 Cl 2 and pentane. Handling, Storage, and Precautions : solid Shvo's catalyst is substantially stable to air.

Here we report an efficient route for synthesizing strigolactones (SLs) and their derivatives. Our method relies on a palladium-catalyzed oxidative carbonylation/carbocyclization/carbonylation/alkoxylation cascade reaction, which involves the formation of three new C-C bonds and a new C-O bond while cleaving one C(sp3)-H bond in a single step. With our versatile synthetic strategy, both naturally occurring and artificial SLs were prepared.

Chemoenzymatic dynamic kinetic resolution (DKR), combining a metal racemization catalyst with an enzyme, has emerged as an elegant solution to transform racemic substrates into enantiopure products, while compatibility of dual catalysis is the key issue. Conventional solutions have utilized presynthesized metal complexes with a fixed and bulky ligand to protect the metal from the enzyme system; however, this has been generally limited to anionic ligands. Herein, we report our strategy to solve the compatibility issue by employing a reliable ligand that firmly coordinates in situ to the metal. Such a reliable ligand offers pi* orbitals, allowing additional metal-to-ligand d-pi* back-donation, which can significantly enhance coordination effects between the ligand and metal. Therefore, we developed an efficient DKR method to access chiral BINOLs from racemic derivatives under dual copper and enzyme catalysis. In cooperation with lipase LPL-311-Celite, the DKR of BINOLs was successfully realized with a copper catalyst via in situ coordination of BCP (L8) to CuCl. A series of functionalized C 2- and C 1-symmetric chiral biaryls could be synthesized in high yields with good enantioselectivity. The racemization mechanism was proposed to involve a radical-anion intermediate, which allows the axial rotation with a dramatic decrease of the rotation barrier.

A highly efficient dehydrogenative carbonylative esterification of allenoic acids using Pd-catalysis was developed, providing a novel approach to synthesizing esterified γ-butyrolactone derivatives with consistently good to excellent results demonstrated across over 50 examples. Additionally, we used a heterogeneous catalyst known as Pd-AmP-MCF and harnessed biomimetic-aerobic-oxidation conditions to facilitate the practical execution of this reaction. Furthermore, our detailed study of γ-butyrolactone products highlighted their potential in synthesizing bioactive compounds.

A novel iron-catalyzed borylation of propargylic acetates leading to allenylboronates has been developed. The method allows the preparation of a variety of di-, tri- and tetrasubstituted allenylboronates at room temperature with good functional group compatibility. Stereochemical studies show that an anti-SN 2' displacement of acetate by boron occurs; this also allows transfer of chirality to yield enantiomerically enriched allenylboronates. The synthetic utility of this protocol was further substantiated by transformations of the obtained allenylboronates including oxidation and propargylation.

The mechanism of dehydrogenation of amines catalyzedby (cyclopentadienone)ironcarbonyl complexes was studied by means of kinetic isotope effect(KIE) measurements, intermediate isolation, and density functionaltheory calculations. The (cyclopentadienone)iron-amine intermediateswere isolated and characterized by H-1 and C-13 NMR spectroscopy as well as X-ray crystallography. The isolatediron-amine complexes are quite stable and undergo a formal beta-hydride elimination to produce imine and iron hydride complexes.The KIEs observed for the iron-catalyzed dehydrogenation of 4-methoxy-N-(4-methylbenzyl)aniline are in accordance with stepwisedehydrogenation. The density functional calculations corroborate astepwise mechanism involving a rate-determining hydride transfer fromamine to iron to yield a metal hydride and an iminium intermediate,followed by a proton transfer from the iminium ion to the oxygen ofthe cyclopentadienone ligand.

Herein, we describe efficient nanogold-catalyzed cycloisomerization reactions of alkynoic acids and allenynamides to enol lactones and dihydropyrroles, respectively (the latter via an Alder-ene reaction). The gold nanoparticles were immobilized on thiol-functionalized microcrystalline cellulose and characterized by electron microscopy (HAADF-STEM) and by XPS. The thiol-stabilized gold nanoparticles (Au0) were obtained in the size range 1.5-6 nm at the cellulose surface. The robust and sustainable cellulose-supported gold nanocatalyst can be recycled for multiple cycles without losing activity.

A novel and sustainable tandem‐catalysis system for asymmetric synthesis is disclosed, which is fabricated by bio‐inspired self‐assembly of artificial arthropod exoskeletons (AAE s) or artificial fungi cell walls ( AFCW s) containing two different types of catalysts (enzyme and metal nanoparticles). The heterogeneous integrated enzyme/metal nanoparticle AAE / AFCW systems, which contain chitosan as the main structural component, co‐catalyze dynamic kinetic resolution of primary amines via a tandem racemization/enantioselective amidation reaction process to give the corresponding amides in high yields and excellent ee. The heterogeneous AAE / AFCW systems display successful heterogeneous synergistic catalysis at the surfaces since they can catalyze multiple reaction cycles without metal leaching. The use of natural‐based and biocompatible structural components makes the AAE / AFCW systems fully biodegradable and renewable, thus fulfilling important green chemistry requirements.

Structurally diverse 1,3-dienes are valuable building blocks in organic synthesis. Herein we report the iron-catalyzed coupling between α-allenyl esters and Grignard reagents, which provides a fast and practical approach to a variety of complex substituted 1,3-dienes. The reaction involves an inexpensive iron catalyst, mild reaction conditions, and provides easy scale up.

A highly efficient regio- and stereoselective heterogeneous palladium-catalyzed hydroboration reaction of enallenes was developed. Nanopalladium immobilized on microcrystalline cellulose (MCC) was successfully employed as an efficient catalyst for the enallene hydroboration reaction. The nanopalladium particles were shown by HAADF-STEM to have an average size of 2.4 nm. The cellulose-supported palladium catalyst exhibits high stability and provides vinyl boron products in good to high isolated yields (up to 90 %). The nanopalladium catalyst can be efficiently recycled and it was demonstrated that the catalyst can be used in 7 runs with a maintained high yield (>80 %). The vinylboron compounds prepared from enallenes are important synthetic intermediates that can be used in various organic synthetic transformations.

This Communication contains an error regarding the structure of (S)-1l, in Scheme 3, which was drawn as the wrong enantiomer. The correct structure of (S)-1l with the correct configuration at the chiral center is shown below. None of the conclusions are affected in any way by this correction.

Herein, we describe an efficient nanocopper-catalyzed Alder-ene reaction of allenynamides. The copper nanoparticles were immobilized on amino-functionalized microcrystalline cellulose. A solvent-controlled chemoselectivity of the reaction was observed, leading to the chemodivergent synthesis of pyrrolines (2,5-dihydropyrroles) and pyrroles. The heterogeneous copper catalyst exhibits high efficiency and good recyclability in the Alder-ene reaction, constituting a highly attractive catalytic system from an economical and environmental point of view.

Herein, we report an electrochemical oxidative palladium-catalyzed carbonylation-carbocyclization of enallenols to afford γ-lactones and spirolactones, which proceeds with excellent chemoselectivity. Interestingly, electrocatalysis was found to have an accelerating effect on the rate of the tandem process, leading to a more efficient reaction than that under chemical redox conditions.

Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydrogenation process, involving several electron-transfer steps, is inspired by oxidations occurring in the respiratory chain. An environmentally friendly and inexpensive iron catalyst together with a hydroquinone/cobalt Schiff base hybrid catalyst as electron-transfer mediator were used for the substrate-selective dehydrogenation reaction of various N-heterocycles. The method shows a broad substrate scope and delivers important heterocycles in good-to-excellent yields.

Transition metal-catalyzed aerobic oxidative reactions using molecular oxygen as terminal oxidant play a significant role in organic synthesis. Benzoquinone (BQ) has been widely used as electron tr...

The assembly of cellulose-based artificial plant cell wall (APCW) structures that contain different types of catalysts is a powerful strategy for the development of cascade reactions. Here we disclose an APCW catalytic system containing a lipase enzyme and nanopalladium particles that transform a racemic amine into the corresponding enantiomerically pure amide in high yield via a dynamic kinetic resolution.

This Review compiles the evolution, mechanistic understanding, and more recent advances in enantioselective Pd-catalyzed allylic substitution and decarboxylative and oxidative allylic substitutions. For each reaction, the catalytic data, as well as examples of their application to the synthesis of more complex molecules, are collected. Sections in which we discuss key mechanistic aspects for high selectivity and a comparison with other metals (with advantages and disadvantages) are also included. For Pd-catalyzed asymmetric allylic substitution, the catalytic data are grouped according to the type of nucleophile employed. Because of the prominent position of the use of stabilized carbon nucleophiles and heteronucleophiles, many chiral ligands have been developed. To better compare the results, they are presented grouped by ligand types. Pd-catalyzed asymmetric decarboxylative reactions are mainly promoted by PHOX or Trost ligands, which justifies organizing this section in chronological order. For asymmetric oxidative allylic substitution the results are grouped according to the type of nucleophile used.