Phosphine‐ and Hydrogen‐Free: Highly Regioselective Ruthenium‐Catalyzed Hydroaminomethylation of Olefins

A highly regioselective ruthenium‐catalyzed hydroaminomethylation of olefins is reported. Using easily available trirutheniumdodecacarbonyl an efficient sequence consisting of a water‐gas shift reaction, hydroformylation of olefins, with subsequent imine or enamine formation and final reduction is realized. This novel procedure is highly practical (ligand‐free, one pot) and economic (low catalyst loading and inexpensive metal). Bulk industrial as well as functionalized olefins react with various amines to give the corresponding tertiary amines generally in high yields (up to 92 %), excellent regioselectivities (n/iso>99:1), and full chemoselectivity in favor of terminal olefins.     

Asymmetric epoxidation with a photoactivated [Ru(salen)] complex

(Nitrosyl)(salen)ruthenium(II) complex 1 was found to serve as an efficient catalyst for the epoxidation of conjugated olefins under photoirradiation, with 2,6-dichloropyridine N-oxide (2) or tetramethylpyrazine N,N'-dioxide as a stoichiometric oxidant. High enantioselectivity was achieved irrespective of the substitution pattern of olefins. The choice of solvent depends on stability of the resulting epoxides: high enantioselectivity is generally observed in the reaction with ethereal solvents, but use of benzene is recommended when the resulting epoxides are acid-sensitive.     

Donor‐Flexible Bis(pyridylidene amide) Ligands for Highly Efficient Ruthenium‐Catalyzed Olefin Oxidation

An exceptionally efficient ruthenium‐based catalyst for olefin oxidation has been designed by exploiting N,N′‐bis(pyridylidene)oxalamide (bisPYA) as a donor‐flexible ligand. The dynamic donor ability of the bisPYA ligand, imparted by variable zwitterionic and neutral resonance structure contributions, paired with the redox activity of ruthenium provided catalytic activity for Lemieux–Johnson‐type oxidative cleavage of olefins to efficiently prepare ketones and aldehydes. The ruthenium bisPYA complex significantly outperforms state‐of‐the‐art systems and displays extraordinary catalytic activity in this oxidation, reaching turnover frequencies of 650 000 h^?1 and turnover numbers of several millions.     

Direct and Tandem Routes for the Copolymerization of Ethylene with Polar Functionalized Internal Olefins

Transition metal catalyzed ethylene copolymerization with polar monomers is a highly challenging reaction. After decades of research, the scope of suitable comonomer substrates has expanded from special to fundamental polar monomers and, recently, to 1,1‐disubstituted ethylenes. Described in this contribution is a direct and tandem strategy to realize ethylene copolymerization with various 1,2‐disubstituted ethylenes. The direct route is sensitive to sterics of both the comonomers and the catalyst. In the tandem route, ruthenium‐catalyzed ethenolysis can convert 1,2‐disubstituted ethylenes into terminal olefins, which can be subsequently copolymerized with ethylene to afford polar functionalized polyolefins. The one‐pot, two‐step tandem route is highly versatile and efficient in dealing with challenging substrates. This work is a step forward in terms of expanding the substrate scope for transition metal catalyzed ethylene copolymerization with polar‐functionalized comonomers.     

An improved protocol for the RuO4-catalyzed dihydroxylation of olefins

[reaction: see text] Dihydroxylation under ruthenium catalysis provides an easy access to syn-diols, although overoxidation is a common side reaction. Furthermore, the high catalyst loadings offset the lower price of ruthenium compared to osmium. In this paper, we present an improved protocol for the RuO(4)-catalyzed syn-dihydroxylation using only 0.5 mol % catalyst under acidic conditions. A variety of olefins can be hydroxylated in good to excellent yields with only minor formation of side products.     

Straightforward synthesis of alpha,beta-unsaturated thioesters via ruthenium-catalyzed olefin cross-metathesis with thioacrylate

The cross-metathesis reaction of S-ethyl thioacrylate with a variety of olefins is effectively catalyzed by using a ruthenium benzylidene olefin metathesis catalyst. This reaction provides a convenient and versatile route to substituted alpha,beta-unsaturated thioesters, key building blocks in organic synthesis.     

Ruthenium catalyzed addition reaction of carboxylic acid across olefins without beta-hydride elimination

The cationic ruthenium catalyst (Cp*RuCl2)2/AgOTf/Ligand promotes the addition reaction of carboxylic acids across olefins without beta-hydride elimination.     

Z-selective homodimerization of terminal olefins with a ruthenium metathesis catalyst

The cross-metathesis of terminal olefins using a novel ruthenium catalyst results in excellent selectivity for the Z-olefin homodimer. The reaction was found to tolerate a large number of functional groups, solvents, and temperatures while maintaining excellent Z-selectivity, even at high reaction conversions.     

Catalytic Intramolecular Ketone Alkylation with Olefins by Dual Activation

Two complementary methods for catalytic intramolecular ketone alkylation reactions with unactivated olefins, resulting in Conia‐ene‐type reactions, are reported. The transformations are enabled by dual activation of both the ketone and the olefin and are atom‐economical as stoichiometric oxidants or reductants are not required. Assisted by Kool’s aniline catalyst, the reaction conditions can be both pH‐ and redox‐neutral. A broad range of functional groups are thus tolerated. Whereas the rhodium catalysts are effective for the formation of five‐membered rings, a ruthenium‐based system that affords the six‐membered ring products was also developed.     

Ruthenium-catalyzed tandem enyne-cross metathesis-cyclopropanation: three-component access to vinyl cyclopropanes

Substituted vinylcyclopropanes are prepared through a ruthenium-catalyzed, tandem three-component coupling between an olefin, alkyne, and diazoester. Grubbs’ 2nd generation (NHC) ruthenium complexes in the presence of ethylene effect a stereoselective enyne-cross metathesis between alkynes and olefins to generate 1,3-substituted dienes. The slow introduction of diazoacetates to this reaction mixture then allows for the regioselective cyclopropanation of the resulting diene. When the olefin reaction partner is just ethylene (i.e., R′ = H), the tandem process is less efficient. In this case, the byproducts provide unique insight into possible catalyst decomposition pathways.     

Unprecedented Selectivity of Ruthenium Iodide Benzylidenes in Olefin Metathesis Reactions

The development of selective olefin metathesis catalysts is crucial to achieving new synthetic pathways. Herein, we show that cis‐diiodo/sulfur‐chelated ruthenium benzylidenes do not react with strained cycloalkenes and internal olefins, but can effectively catalyze metathesis reactions of terminal dienes. Surprisingly, internal olefins may partake in olefin metathesis reactions once the ruthenium methylidene intermediate has been generated. This unexpected behavior allows the facile formation of strained cis‐cyclooctene by the RCM reaction of 1,9‐undecadiene. Moreover, cis‐1,4‐polybutadiene may be transformed into small cyclic molecules, including its smallest precursor, 1,5‐cyclooctadiene, by the use of this novel sequence. Norbornenes, including the reactive dicyclopentadiene (DCPD), remain unscathed even in the presence of terminal olefin substrates as they are too bulky to approach the diiodo ruthenium methylidene. The experimental results are accompanied by thorough DFT calculations.     

Switch in Selectivity for Formal Hydroalkylation of 1,3‐Dienes and Enynes with Simple Hydrazones

Controlling reaction selectivity is a permanent pursuit for chemists. Regioselective catalysis, which exploits and/or overcomes innate steric and electronic bias to deliver diverse regio‐enriched products from the same starting materials, represents a powerful tool for divergent synthesis. Recently, the 1,2‐Markovnikov hydroalkylation of 1,3‐dienes with simple hydrazones was reported to generate branched allylic compounds when a nickel catalyst was used. As part of the effort, shown here is that a complete switch of Markovnikov to anti‐Markovnikov addition is obtained by changing to a ruthenium catalyst, thus providing direct and efficient access to homoallylic products exclusively. Isotopic substitution experiments indicate that no reversible hydro‐metallation across the metal‐π‐allyl system occurred under ruthenium catalysis. Moreover, this protocol is applicable to the regiospecific hydroalkylation of the distal C=C bond of 1,3‐enynes.     

Asymmetric epoxidation of conjugated olefins with dioxygen

A complex situation: Asymmetric epoxidation of conjugated olefins was achieved at room temperature using ruthenium complex 1 as the catalyst and air as the oxidant to give epoxides in up to 95?%?ee. When the product was acid sensitive, the reaction was carried out at 0?°C under oxygen.     

Mn(III)‐salan/graphene oxide/magnetite nanocomposite as a highly selective catalyst for aerobic epoxidation of olefins

A nanocomposite was synthesized using carbon‐coated Fe₃O₄ nanoparticle‐decorated reduced graphene oxide as a convenient and efficient supporting material for grafting of a manganese–reduced Schiff base (salan) complex via covalent attachment. The nanocomposite was characterized using X‐ray diffraction, Fourier transform infrared and diffuse reflectance UV–visible spectroscopies, inductively coupled plasma atomic emission spectrometry and scanning electron microscopy. It was evaluated as a catalyst for the aerobic epoxidation of olefins in acetonitrile in combination with a sacrificial co‐reductant (isobutyraldehyde). The catalytic performance of the heterogeneous system of the Mn–salan complex is superior to that of the homogeneous one. The catalyst activity strongly depends on the reaction temperature and nature of the solvent. The epoxide yield increases with the nucleophilic character of the olefin. The nanocomposite performs well as an epoxidation catalyst for electron‐rich and conjugated olefins. It can be recovered from the reaction medium by magnetic decantation and reused, maintaining good catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Organic Ligand‐Free Hydroformylation with Rh Particles as Catalyst†

Summary of main observation and conclusion An efficient and organic ligand-free heterogeneous catalytic system for hydroformylation of olefins is highly desirable for both academy and industry.In this study,simple Rh black was employed as a heterogeneous catalyst for hydroformylation of olefins in the absence of organic ligand.The Rh black catalyst showed good catalytic activity for a broad substrate scope including the aliphatic and aromatic olefins,affording the desired aldehydes in good yields.Taking the hydroformylation of ethylene as an example,86%yield of propanal and TOF of 200 h-1 were obtained,which was superior to the reported homogeneous catalytic systems.In addition,the catalyst could be reused five times without loss of activity under identical reaction conditions,and the Rh leaching was negligible after each cycle.     

Ruthenium catalyzed desymmetrization of diazabicyclic olefins to access heteroaryl substituted cyclopentenes through C–H activation of phenylazoles

The first ruthenium catalyzed redox-neutral C–H activation strategy for the ring-opening of diazabicyclic olefins via C–H bond cleavage of phenyl azoles is reported. The developed method offers a novel route to functionalized cyclopentenes by employing less-expensive ruthenium catalyst and readily accessible biologically significant heteroarenes. The present protocol is a merger of the C–H activation of phenyl substituted heteroaromatics and subsequent β-nitrogen elimination of diazabicyclic olefins.     

Cyclic Alkyl Amino Carbene (CAAC) Ruthenium Complexes as Remarkably Active Catalysts for Ethenolysis

An expanded family of ruthenium‐based metathesis catalysts bearing cyclic alkyl amino carbene (CAAC) ligands was prepared. These catalysts exhibited exceptional activity in the ethenolysis of the seed‐oil derivative methyl oleate. In many cases, catalyst turnover numbers (TONs) of more than 100 000 were achieved, at a catalyst loading of only 3 ppm. Remarkably, the most active catalyst system was able to achieve a TON of 340 000, at a catalyst loading of only 1 ppm. This is the first time a series of metathesis catalysts has exhibited such high performance in cross‐metathesis reactions employing ethylene gas, with activities sufficient to render ethenolysis applicable to the industrial‐scale production of linear α‐olefins (LAOs) and other terminal‐olefin products.     

Fujiwara–Moritani Reaction of Weinreb Amides using a Ruthenium‐Catalyzed C−H Functionalization Reaction

The ruthenium‐catalyzed Fujiwara–Moritani reaction (oxidative‐Heck reaction) of Weinreb amides is reported herein. The reaction affords exclusively ortho‐C?H olefination products, has excellent substrate scope and tolerates halogen functionalities, which increase the synthetic utility of the method. A variety of activated olefins as well as styrenes can be employed as coupling partners.     

Immobilization and Continuous Recycling of Photoredox Catalysts in Ionic Liquids for Applications in Batch Reactions and Flow Systems: Catalytic Alkene Isomerization by Using Visible Light

A catalytic (E)‐ to (Z)‐isomerization of olefins using a photoredox catalyst under mild reaction conditions is presented. A variety of (Z)‐alkenes can be prepared in the presence of visible light. A new reaction system allows an easy and efficient scale‐up, as well as a continuous flow process in which the photocatalyst is immobilized in an ionic liquid and continuously recycled by simple phase separation.     

Synthesis of Dendritic BINAP Ligands and Their Applications in Asymmetric Hydrogenation

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