A New Method for the Transformation of Alkenes intoα, β-Unsaturated Ketones via Cycloaddition with Dichloroketene

A new synthetic method is described here to obtain α, β-unsaturated ketones through alkenes through a sequence involving f (1) cycloaddition of alkenes with dichloroketene, (2) dechlorination of adducts, (3)acidpromoted ring-opening isomerization ofcyclobutanones in CF3 CO2H.

'STEREOSELECTIVE SYNTHESIS OF TRISIJBSTITUTED ALKENES VIA,TITANOCENOCYCLES

By previously reported modified Masai-Rausch method of synthesizing titanocenocycles,followed by acid hydrolysis,trisubstituted al-kenes were synthesized,yields obtained are higher than that reported in literatures.Starting from unsymmetrical alkyne substrates,twelve different types of substituted alkenes were synthesized,among which only two were found single component,others were of mixed isomers.Beside conventional analytical methods,the NMR spectral analysis of titanocenoheterocycle intermediates and the products were used to identify the isomeric structures as well as their relative contents.

Hydrogenation of Alkenes with NaBH4, CH3CO2H, Pd/C in the Presence of O- and N-Benzyl Functions

NaBH4, CH3CO2H, Pd/C has been described as an effective reagent system to hydrogenate alkenes. Here, we show that the hydrogenation occurs chemoselectively, making it possible to hydrogenate alkenes under Pd/C catalysis with hydrogen created in situ without O- or N-debenzylation.

(Z)-a-Selanyl Alkenyl Grignard Reagents as Convenient Precursors for Stereoselective Synthesis of Trisubstituted Alkenes

Z)-a-Selanyl alkenyl Grignard reagents 2 were prepared conveniently by treatment of a-bromovinylselenides 1 with magnesium filings in THF. Intermediates 2 were reacted with alkyl iodides in the presence of CuI or Pd(PPh3)4 to afford (Z)-1,2-disubstituted vinylselenides 3, which were cross-coupled with Grignard reagents in the presence of (PPh3)2NiCl2 to give trisubstituted alkenes 4 stereoselectively in good yields.

Visible Light-Induced[3+2]Annulation Reaction of Alkenes with Vinyl Azides:Direct Synthesis of Functionalized Pyrroles

A photocatalytic[3+2]annulation of alkenes with vinyl azides was developed under irradiation by visible light in the presence of organic dye photocatalysts.Broad substrate scope and high functional group tolerance were demonstrated by more than 50 examples.The reaction provides a novel and efficient method for the synthesis of polyfunctionalized pyrroles under very mild metal-free conditions without other additives.

Photocatalyzed ditrifluoromethylthiolation of alkenes with CF_(3)SO_(2)Na

Since the first report of sodium trifluoromethanesulfinate(CF_(3)SO_(2)Na) as an electrophilic trifluoromethylthiolation reagent in 2015,there has been no breakthrough in research in this field.Herein,we disclose an unprecedented usage of CF_(3)SO_(2)Na as a radical trifluoromethylthiolation reagent.A photocatalyzed ditrifluoromethylthiolation of alkenes with CF_(3)SO_(2)Na in the presence of PPh_(3) and catalytic copper has been developed.Interestingly,either Ir[(p-Fppy)_(2)(bpy)]PF_6 or Ir(ppy)_(3) could facilitate this transformation.Mechanistic studies indicate that initiation of the radical chain proceeded via two different photocatalytic quenching mechanisms.This protocol provides a practical method for the construction of diverse vicinal ditrifluoromethylthiolated compounds.

Palladium(Ⅱ)-Catalyzed Markovnikov Hydroalkynylation of Unactivated Terminal Alkenes

Alkynes are versatile synthons in organic synthesis,as well as important structural moieties in bioactive molecules.Recently,transition metal-catalyzed hydroalkynylation of alkenes has been developed with reactive alkenes and alkenes bearing directing groups.However,the regioselective hydroalkynylation of simple alkenes is still challenging.Herein,we have developed a palladium-catalyzed Markovnikov hydroalkynylation of unactivated terminal alkenes,which provides an efficient approach for the synthesis of branched alkynyl compounds under mild conditions.This reaction features excellent functional group tolerance,good reaction yields and excellent regioselectivity.Moreover,the asymmetric hydroalkynylation reaction has also been achieved with moderate enantioselectivity by introducing a sterically bulky chiral Pyox ligand.

S-,P-stabilized bromoallenes for modular allenylborylation of alkenes

Simultaneously forming a carbon-carbon and a carbon-heteroatom bond in a single step through transition metal-catalyzed alkene difunctionalization strategy has emerged as a powerful tool for synthetic organic chemistry.Due to the uncontrollable reactivity,direct cross-coupling with bromoallenes as the building blocks for the selective allenation and borylation remains challenging.We herein report a new type of S-and P-stabilized bromoallenes for palladium-catalyzed modular allenation and borylation of alkenes to the divergent synthesis of multiply functionalized allenes in a highly regio-and diastereoselective manifold.The reaction features broad substrate scope and wide functional group compatibility,thus providing a straightforward method to install allenyl and boryl groups across alkenes.Control experiments highlight the crucial importance of S-,P-stabilization for the oxidative insertion of Pd-species into the allenyl-Br bond.The facile syntheses of bioactive allenic steroids and exocyclic allenes demonstrate the synthetic utility of this protocol.

Trisubstituted alkenes featuring aryl groups:stereoselective synthetic strategies and applications

In recent years,the synthesis and application of alkenes have attracted increased attention.Triphenylethenes(TriPEs)have lower molecular torsion than tetraphenylethenes(TPEs),which helps to balance the degree of conjugation and the aggregation-induced emission(AIE)effect.The geometry of double bonds has a significant impact on luminescence.Therefore,it is essential to provide a comprehensive summary of the stereoselective synthetic strategies for trisubstituted alkenes.In this review,common strategies for the stereoselective synthesis of alkenes are described,with an emphasis on the origin of stereoselectivity and the types of substrates.In addition,the AIE properties of TriPE and its applications in optoelectronic devices,stimuli-responsive materials,sensors,and therapies were discussed.

Diastereoselective and Enantioselective Nickel-Catalyzed Reductive Coupling of Imines and Unactivated Alkenes

Herein we report a method for highly diastereoselective and enantioselective nickel-catalyzed reductive coupling of imines and unactivated alkenes.A monodentate chiral spiro phosphoramidite ligand is the key to controlling the enantioselectivity.This efficient,straightforward method allows for the construction of chiral benzocyclic and indole-fused cyclic amines with two contiguous stereogenic centers in good yields from readily accessible starting materials.

Difluoroalkylative carbonylation of alkenes to access carbonyl difluoro-containing heterocycles:convenient synthesis of gemigliptin

Fluorinated heterocycles play a vital role in pharmaceutical and agrochemical industries.Hence,rapid and efficient construction of fluorinated heterocycles remains highly demanded.Herein,a difluoroalkylative carbonylative cyclization of unactivated alkenes and ethylene gas enabled by palladium catalysis has been developed for the first time toward the synthesis ofα-carbonyl difluoro-modified glutarimides.This procedure can also be applied to the synthesis of Ge Migliptin which is a medicine approved for the treatment of type 2 diabetes mellitus.

Difluoroalkylation/Lactonization of Alkenes with BrCF_(2)CO_(2)K via Photoredox Catalysis:Access toα,α-Difluoro-γ-lactones

Due to its unique electronic properties,the difluoromethylene group(CF2)has served as a valuable unity in the design of biologically active molecules.Sinceγ-lactones display a broad range of biological properties,α,α-difluoro-γ-lactones may exhibit unexpected biological activities,and thus their synthesis has received increasing attention.Traditional synthetic methods suffer from tedious multi-step processes,and very few effective methods have been reported recently.Herein,we describe the difunctionalization of alkenes with BrCF_(2)CO_(2)K under photoredox catalysis with the use of a boron-Lewis acid for the access toα,α-difluoro-γ-lactones.In this transformation,the alkene substrates and the used reagents,including BrCF_(2)CO_(2)K and the boron-Lewis acid,PhB(OH)2 or BF3·THF,are cheap and widely available.High efficiency and atom economy may make this protocol attractive.

Visible-light-induced direct hydrodifluoromethylation of alkenes with difluoromethyltriphenylphosphonium iodide salt

Photoredox-catalyzed hydrodifluoromethylation of alkenes has become an effective method to introduce difluoromethyl group into organic molecules.As the reported methods involve either photocatalysts or superstoichiometric amounts of additives,we herein describe a simple alternative without using photocatalyst or additive for the hydrodifluoromethylation of alkenes,through photoactivation of difluoromethyltriphenylphosphonium iodide salt.Mechanistic studies shed light on how the transformation takes place.

Electrophotocatalytic Reductive 1,2-Diarylation of Alkenes with Aryl Halides and Cyanoaromatics

Comprehensive Summary The radical-mediated reductive functionalization of aryl halides has been extensively studied.However,the related radical-mediated intermolecular reductive 1,2-diarylation of alkenes,using aryl halides as aryl radical sources,remains unexplored.Herein,a new electrophotocatalytic intermolecular reductive 1,2-diarylation of alkenes is reported using aryl halides and cyanoaromatics to produce polyarylated alkanes.Using synergistic cathodic reduction and visible-light photoredox catalysis,various electron-rich and electron-deficient aryl halides are combined with various alkenes and cyanoaromatics to characterize the broad substrate scope,excellent functional group compatibility,and excellent selectivity of this reaction.Mechanistic investigations reveal that this reaction may proceed via a radical process initiated by the reductive generation of aryl radicals from aryl halides and terminated by radical-radical coupling with cyanoaromatic radical anions.

Nickel/Quinim Enabled Asymmetric Carbamoyl-Acylation of Unactivated Alkenes

Transition metal-catalyzed difunctionalization of tethered alkene has emerged as a prevailing tool for the expedient construction of synthetically valuable cyclic compounds.However,most efforts have been devoted to the reaction of styrene-type substrates due to their rigid scaffold and high reactivity.With respect to the difunctionalization of nonaromatic tethered olefin,especially the mono-substituted alkene,still remains largely underdeveloped.Herein,we disclose a nickel/Quinim complex and TBADT-cocatalyzed asymmetric carbamoyl-acylation of unactivated alkene tethered on nonaromatic carbamoyl chlorides with diverse aldehydes.The reaction exhibits broad substrate scope with good functional group tolerance,as well as high reaction efficiency and enantioselectivity.Both monosubstituted and 1,1-substituted alkenes can work well with either aliphatic or aromatic aldehydes under the current protocol,providing convenient access to an array of medicinally useful chiralγ-lactams derivatives bearing a convertible acyl functionality.This reaction showcases more application possibilities of the chiral Quinim ligand in the future asymmetric catalytic transformations.

Nickel-catalyzed hydromonofluoromethylation of unactivated alkenes for expedient construction of primary alkyl fluorides

A nickel-catalyzed direct hydromonofluoromethylation of unactivated olefins with industrial raw fluoroiodomethane is developed,furnishing various primary alkyl fluorides in a step-economic manner.The key factor to success is the use of pyridine-oxazoline as ligand and(MeO)_(2)MeSiH as the hydrogen source.This transformation demonstrates high efficiency,mild conditions,good functional-group compatibility and great potential in the drug discovery.

Advances in Transition-Metal-Catalyzed Hydrogermylation of Alkenes and Alkynes

Hydrogermylation of alkenes and alkynes provides a straightforward synthetic route to organogermanium compounds that have been found applications in organic synthesis,medicinal chemistry,and material science.This paper reviews the advances in transition-metal-catalyzed hydrogermylation of unsaturated carbon-carbon bonds,including alkenes,alkynes,dienes,and allenes,with the objective of providing readers with the status of the field.Progress,problems,and perspectives in this field are discussed.

Pd-catalyzed diastereoselective 1,1-diarylation of 1,1-disubstituted alkenes enabling the modular synthesis of 1,1,2,2-tetraarylethanes

The highly diastereoselective dicarbofunctionalization of substituted olefins still remains a daunting challenge in synthetic chemistry.Herein,we report a Pd-catalyzed diastereoselective 1,1-diarylation of 1,1-diarylethylene with chelation group free to enable the modular synthesis of smart material candidates,1,1,2,2-tetraarylethanes(TAEs),which represent the first protocol by assembling four different aryl groups into ethane motif.Preliminary mechanistic experiments suggest that the crucial Pd–H species generated in situ do not disengage from the alkene intermediate during the reaction.

Recent Advances in Hydrometallation of Alkenes and Alkynes via the First Row Transition Metal Catalysis

Hydrometallation of alkenes and alkynes provides a straightforward route to access alkyl- or alkenyl-metal reagents, which have a wide rangeof applications in organic transformations. In recent years, the first row transition metals （such as copper, nickel, cobalt, iron, etc.） have emerged highactivity and selectivity in this area with the aid of a variety of ligands. This review covers the recent advances in the hydrometallation of minimally func-tionalized unsaturated C--C bonds （including alkenes, alkynes, dienes, allenes, enynes, etc.）, as well as transformations involving catalytic hydrometalla-tion process via the first row transition metal catalysis.

Recent Advances on the Electrochemical Difunctionalization of Alkenes/Alkynes

Electroorganic synthesis is an emerging area of high impact research in organic chemistry, which is considered as one of the green and efficient methods and attracts growing research attention. In this review, we summarized comprehensively the recent literature reports on the electrochemical oxidative difunctionalization of unsaturated C—C bonds. The reaction types described in this review included electrochemical intermolecular cyclization, electrochemical intramolecular cyclization, and electrochemical difunctionalization of alkenes/alkynes. This review focuses on the discussion of its synthetic generality for the preparation of functionalized compounds and the related electrochemical oxidative reaction mechanism.