Coupling Of Alkenes Research Articles

Multicomponent alkene azidoarylation by anion-mediated dual catalysis.

Molecules that containthe β-arylethylaminemotif have applications in the modulation of pain, treatment of neurological disorders and management of opioid addiction, among others, making it a privileged scaffold in drug discovery1,2. De novo methods for their assembly are reliant on transformations that convert a small class of feedstocks into the target compounds via time-consuming multistep syntheses3-5. Synthetic invention can drive the investigation of the chemical space around this scaffold to further expand its capabilities in biology6-9. Here we report the development of a dual catalysis platform that enables a multicomponent coupling of alkenes, aryl electrophiles and a simple nitrogen nucleophile, providing single-step access to synthetically versatile and functionally diverse β-arylethylamines. Driven by visible light, two discrete copper catalysts orchestrate aryl-radical formation and azido-group transfer, which underpin an alkene azidoarylation process. The process shows broad scope in alkene and aryl components and an azide anion performs a multifaceted role bothas a nitrogen source and in mediating the redox-neutral dual catalysis via inner-sphere electron transfer10,11. The synthetic capabilities of this anion-mediated alkene functionalization process are likely to be of use in a variety of pharmaceutically relevant and wider synthetic applications.

Intramolecular Alkene–Alkene Coupling via Rh(III)-Catalyzed Alkenyl sp2 C–H Functionalization: Divergent Pathways to Indene or α-Naphthol Derivatives

Intramolecular Alkene–Alkene Coupling via Rh(III)-Catalyzed Alkenyl sp² C–H Functionalization: Divergent Pathways to Indene or α-Naphthol Derivatives

Chromium-Catalyzed Allylic Defluorinative Ketyl Olefin Coupling

Herein we report a chromium-catalyzed allylic defluorinative ketyl olefin coupling between aldehydes and α-trifluoromethyl alkenes, which provides novel and efficient access to diverse gem-difluorohomoallylic alcohols. Remarkably, the high chemoselectivity of this reaction enables the conversion of the formyl moiety in the presence of various easily reducible functionalities including ketone, organohalides, aziridine, sulfone, alkyne, and unactivated alkene. The utility of this method is demonstrated by various simple derivatizations of the attached hydroxyl group of the coupling products. The preliminary mechanistic investigations suggest a reaction pathway with a rate-limiting C-C forming step followed by facile β-fluoro elimination.

Photoredox Reductive Coupling of Olefins with Aryl Chlorides through the Carbon Dioxide Radical Anion

Photoredox Reductive Coupling of Olefins with Aryl Chlorides through the Carbon Dioxide Radical Anion

Dual Catalysis Relay: Coupling of Aldehydes and Alkenes Enabled by Visible-Light and NHC-Catalyzed Cross-Double C–H Functionalizations

Dual Catalysis Relay: Coupling of Aldehydes and Alkenes Enabled by Visible-Light and NHC-Catalyzed Cross-Double C–H Functionalizations

Anodic Olefin Coupling Reactions: Elucidating Radical Cation Mechanisms and the Interplay between Cyclization and Second Oxidation Steps.

Anodic olefin coupling reactions generate new bonds and ring skeletons through a net two electron process that reverses the polarity of a known, electron-rich functional group. While much of the early work on the mechanism of these reactions focused on the initial oxidation and cyclization steps of the process, the second oxidation step also plays a central role in determining the success of the reaction. Evidence supporting this observation is presented, along with evidence that optimization of this second oxidation step is not enough to pull a poor cyclization to the desired product. Successful cyclization reactions require optimization of both processes.

Mechanism and selectivity on IrIII/RhIII-catalyzed coupling of terminal alkenes and dioxazolones: A DFT study

• The mechanism and Selectivity on amidation of terminal alkenes with the nitrene precursors was explored with the aid of DFT calculations. Additionally, influence of the catalyst Ir(III) vs Rh(III) on the selectivity of above reactions was also elucidated. The Cp*IrIII-catalyzed coupling of terminal alkenes with dioxazolones to achieve C H amidation was studied theoretically with the aid of the density functional calculations. Employing the Ir=nitrenoid intermediate species involved in the reaction mechanism, the Ir N R bonding nature was analyzed based on LUMO/HOMO interactions. Especially, the branch-selectivity with Cp*Ir(III) as the catalyst, the influence of Ir(III) vs Rh(III) on branch/linear selectivity, and the impossibility of aziridination were elucidated. This work provided further understanding and beneficial information for designing novel related selective reactions.

Iron-Catalyzed Skeletal Conversion of Lathyrane to Premyrsinane Euphorbia Diterpenes and Their Cytotoxic Activities

Two new premyrsinane-type diterpenes (2 and 3) as diastereomers were synthesized from lathyrane-type diterpene euphorbia factor L3 (1) for the first time via an efficient Fe(acac)3-catalyzed skeleton conversion process. This conversion features a biogenetically inspired strategy that relies on a concise reductive olefin coupling involving intramolecular Michael addition with free radicals. The structures of 2 and 3 were elucidated by a combination of the interpretation of their spectroscopic data and single-crystal X-ray diffraction analysis. The premyrsinane diterpenes 2 and 3 exhibited cytotoxic activity against the 4T1 breast cancer cell line, while the parent compound euphorbia factor L3 (1) was inactive. The current results not only confirmed the biogenetic relationship between lathyranes and premyrsinanes for the first time but also suggested a novel method for the preparation of naturally rare premyrsinane diterpenes with high bioactivity from the more abundant natural lathyrane diterpenes.

Synthesis of Spirocycles via Ni-Catalyzed Intramolecular Coupling of Thioesters and Olefins.

A nickel-catalyzed intramolecular coupling of thioesters and olefins has been developed for the efficient synthesis of spirocycles, a privileged scaffold commonly found in natural products. This transformation is characterized by the simultaneous transfer of both acyl and thiol moieties to the alkene, with the suppression of decarbonylation and β-hydrogen elimination. Initial mechanistic investigations are consistent with an oxidative addition/olefin insertion/reductive elimination mechanism. The incorporated methylene sulfide substituent can undergo a variety of further reactions to increase molecular diversity and complexity. These results demonstrate that thioester derivatives can be used as powerful building blocks for the assembly of complex scaffolds.

Synthesis and Structural Implication of the JKLMN-Ring Fragment of Caribbean Ciguatoxin C-CTX-1

Synthesis of the JKLMN-ring fragment of Caribbean ciguatoxin C-CTX-1, the causative toxin of ciguatera fish poisoning in the Caribbean Sea and the Northeast Atlantic areas, is described in detail. Key to the synthesis are a [2,3]-sigmatropic rearrangement to construct a seven-membered α-hydroxy exo-enol ether, stereoselective construction of an angular tetrasubstituted stereogenic center on the seven-membered M-ring by a hydrogen atom transfer-based reductive olefin coupling, Suzuki-Miyaura coupling of the KLMN-ring enol phosphate with a highly congested M-ring, and silica gel-mediated epoxide ring opening to form the J-ring. Comparison of the nuclear magnetic resonance spectroscopic data for the synthesized fragment with those for the natural product provided support for the formerly assigned structure of the N-ring in the right-hand terminal of C-CTX-1.

Catalytic Reductive Cross Coupling and Enantioselective Protonation of Olefins to Construct Remote Stereocenters for Azaarenes.

A novel enantioselective protonation protocol that is triggered by reductive cross coupling of olefins is reported. When under cooperative photoredox and chiral hydrogen-bonding catalytic conditions and using a terminal reductant, various α-branched vinylketones with diverse vinylazaarenes could provide important enantioenriched azaarene derivatives containing tertiary stereocenters at their remote δ-position with high yields and enantioselectivities. This reaction system is also suitable for α-branched vinylazaarenes, thus successfully assembling elusive 1,4-stereocenters. The convenient late-stage modifications of products, especially the formation of remote ε-tertiary and ε-heteroquaternary carbon stereocenters, further highlight the important synthetic value of this method. Control experiments and density functional theory (DFT) calculations were conducted to elucidate the plausible reaction mechanism and origins of regioselectivity and stereoselectivity.

Photo-Mediated Intermolecular Coupling of Alkenes with Ketones via Acyloxy Nitroso Compounds.

An atom-economic intermolecular radical addition reaction of acyloxy nitroso compounds to electron-deficient alkenes mediated by visible light is reported. The starting nitroso derivatives are readily prepared by oxidation of the corresponding oximes prepared from ketones and the overall transformation represents an oxidative coupling of a ketone with a Michael acceptor. The cascade proceeds smoothly under mild conditions, providing a series of valuable functionalized oximes in moderate to good yields. Mechanistic studies suggest that these cascades proceed via addition/coupling processes that are controlled by the persistent radical effect (PRE) with NO acting as the persistent species.

Organophotoredox-Catalyzed Three-Component Coupling of Heteroatom Nucleophiles, Alkenes, and Aliphatic Redox Active Esters.

This manuscript describes a visible-light-mediated organophotoredox catalytic process for vicinal difunctionalization of alkenes using heteroatom nucleophiles and aliphatic redox active esters. A wide range of heteroatom nucleophiles including alcohols, water, carboxylic acids, amides, and halogens can be used for this reaction. This radical relay type reaction allows forging of C(sp3)-C(sp3) with a carbon-centered radical and C(sp3)-heteroatom bonds with a benzyl cation on the vinylarenes with complete regioselectivity in a single step.

Carbonylative coupling of simple alkanes and alkenes enabled by organic photoredox catalysis.

A visible-light-driven direct carbonylative coupling of simple alkanes and alkenes via the combination of a hydrogen atom transfer process and photoredox catalysis has been demonstrated. Employing the N-alkoxyazinium salt as the oxidant and the precursor of an oxygen radical, a variety of α,β-unsaturated ketones could be obtained in a metal-free fashion.

Ruthenium(II)-catalyzed C-H activation and (4+2) annulation of aromatic hydroxamic acid esters with allylic amides.

A (4+2) annulation under Ru(II)-catalysis is reported using aromatic hydroxamic acid esters as the oxidizing directing group and allylic amides as unactivated olefin coupling partners, delivering a wide variety of aminomethyl isoquinolinones in good to excellent yields. This annulation is distinctive as allylic congeners typically result in allylation and not the annulation. Late-stage derivatization of a bioactive synthetic bile acid has been showcased.

Fe-catalyzed Fukuyama-type indole synthesis triggered by hydrogen atom transfer.

Fe, Co, and Mn hydride-initiated radical olefin additions have enjoyed great success in modern synthesis, yet the extension of other hydrogen radicalophiles instead of olefins remains largely elusive. Herein, we report an efficient Fe-catalyzed intramolecular isonitrile–olefin coupling reaction delivering 3-substituted indoles, in which isonitrile was firstly applied as the hydrogen atom acceptor in the radical generation step by MHAT. The protocol features low catalyst loading, mild reaction conditions, and excellent functional group tolerance.

Photoinduced Dearomatizing Three-Component Coupling of Arylphosphines, Alkenes, and Water.

A unique photoinduced reaction that couples a triarylphosphine, an alkene, and water to produce 2-(cyclohexa-2,5-dienyl)ethylphosphine oxide is reported herein. The alkene inserts into a C(aryl)-P bond of the arylphosphine, the aryl ring is dearomatized into the cyclohexadienyl ring, and the phosphorus is oxidized. The three components are all readily available, and their intermolecular coupling significantly increases molecular complexity. The products formed are applicable to the Wittig olefination.

Photoinduced Dearomatizing Three‐Component Coupling of Arylphosphines, Alkenes, and Water

AbstractA unique photoinduced reaction that couples a triarylphosphine, an alkene, and water to produce 2‐(cyclohexa‐2,5‐dienyl)ethylphosphine oxide is reported herein. The alkene inserts into a C(aryl)−P bond of the arylphosphine, the aryl ring is dearomatized into the cyclohexadienyl ring, and the phosphorus is oxidized. The three components are all readily available, and their intermolecular coupling significantly increases molecular complexity. The products formed are applicable to the Wittig olefination.

Redox-Neutral Propargylic C–H Functionalization by Using Iron Catalysis

AbstractIn spite of their rich stoichiometric chemistry, cyclopentadienyliron(II) dicarbonyl complexes are rarely used as catalysts in organic synthesis. Inspired by precedents in the chemistry of cationic olefin complexes and neutral allylmetal species, our group has developed a coupling of alkynes or alkenes with aldehydes and other carbonyl electrophiles to give homopropargylic and homoallylic alcohols, respectively, by using a substituted cyclopentadienyliron(II) dicarbonyl complex as the catalyst. In this article, we first contextualize this development within the conceptual background of C–H functionalization chemistry and relative to key stoichiometric precedents. We then give an account of our group’s discovery and development of the catalytic α-functionalization of alkenes and alkynes with electrophilic reagents.IntroductionPreliminary Stoichiometric WorkHydroxyalkylation Development and ScopeConclusions and Future Directions

Tuning of active sites in M/TiO2 for photocatalytic cyanation of olefins with high regioselectivity

The detailed structure of active sites plays an important role for the determination of catalytic performance. Herein, catalytic active sites of M/TiO2 for photocatalytic cyanation of olefins are tuned by delicate manipulation of the metal kinds, metal loading amount and pretreatment processes. It was found that the 0.1% Pt/P25 catalyst reduced at 300 °C possessed high metal dispersion and suitable oxygen defects on TiO2, and thus exhibited the best catalytic performance with high specific speed of time yield and high selectivity. A wide scope of olefin substrates could be converted to the corresponding nitriles with high atom efficiency and anti-Markovnikov regioselectivity under mild conditions for the optimized Pt/P25 catalyst. The reaction mechanism based on radical coupling of acetonitrile and olefins was also discussed. This approach offers an environmental-friendly platform for the selective activation of C-H bonds of acetonitrile and will bring potential applications for hydrofunctionalization of olefins.