(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.

One-pot Synthesis,Characterization and Crystal Structure Determination of Novel 1,4,5-Trisubstituted 1,2,3-Triazole with Two Conformational Isomers:1-Benzyl-5-((4-methoxyphenyl)ethynyl)-4-phenyl-1H-1,2,3-triazole

The title compound l-benzyl-5-（（4-methoxyphenyl）ethynyl）-4-phenyl-1H-1,2,3-triazole（C24H19N3O） was designed and synthesized using one-pot strategy and structural characterization was done by single-crystal X-ray diffraction,NMR,IR and MS.This compound was crystallized out from an ethanolic solution in triclinic system,space group P1 with a =9.9038（9）,b = 10.2928（9）,c = 18.8715（19）A°,α = 103.541（6）,β = 90.507（7）,γ = 97.157（7）°,V =1854.2（3） A°3,Z = 4,crystal size（mm） = 0.25 × 0.1 × 0.1 and R（int） = 0.068.Its asymmetric unit contains two independent molecules.The crystal structure of the title compound is stabilized by intramolecular interactions of types C-H…N and C-H…O.Additionally,X-ray analysis reveals obvious C-H…π,π-π stacking interactions between two adjacent aromatic ring planes.

Co/Fe Dual Catalysis for Sequential Hydrosilylation-Isomerization:Access to Trisubstituted(E)-Alkenyl Silanes from Terminal Alkynes

By rational modification of electronic and steric properties of pincer ligands,a Co/Fe dual catalyst system is developed for one-pot sequential Markovnikov alkyne hydrosilylation and stereoselective alkene isomerization.The protocol provides an atom-economical and efficient approach to trisubstituted(E)-alkenyl silanes from widely accessible terminal alkynes with high regio-and stereoselectivities under mild conditions.The utility of this reaction was demonstrated by gram-scale synthesis and derivatization of bioactive molecules.The radical clock and trapping experiments indicated that radical pathway might be operative in the alkene isomerization step.

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.

Iron Catalyzed Isomerization of a-Alkyl Styrenes to Access Trisubstituted Alkenes

Main observation and conclusion Stereoselective isomerization of a-alkyl styrenes is accomplished using a new iron catalyst supported by phosphine-pyridine-oxazoline(PPO)ligand.The protocol provides an atom-efficient and operationally simple approach to trisubstituted alkenes in high yields with excellent regio-and stereoselectivities under mild conditions.The results of deuterium-labelling and radical trap experiments are consistent with an iron-hydride pathway involving reversible alkene insertion andβ-H elimination.

Enantioselective one-pot synthesis of β-sulfonyl ketones and trisubstituted tetrahydrothiophenes via β-elimination/cycloaddition sequence

A mild and efficient enantioselective one-pot synthesis of β-sulfonyl ketones and trisubstituted tetrahydrothiophenes via introducing 1,4-dithiane-2,5-diol to the simple kinetic resolution of β-sulfonyl ketones has been described herein. The one-pot reaction sequence including kinetic resolution and cascade sulfa-Michael/Aldol reaction proceeded successively to afford corresponding sulfonyl ketones and tetrahydrothiophenes with high enantioselectivities（85%-98% ee and 84%-95% ee）.

Stereoselective Synthesis of (E)-α-Aryltellurenylvinyl- stannanes and Their Application in the Synthesis of Stereodefined Trisubstituted Alkenes

E)-α-Aryltellurenylvinylstannanes have been synthesized stereoselectively via the hydrozirconation of alkynyl- stannanes, followed by the reactions with aryltellurenyl iodides. (E)-α-Aryltellurenylvinylstannanes can undergo sequential cross coupling reactions with both electrophiles and nucleophiles in the presence of transition metal complexes to form two carbon-carbon bonds in the same olefinic carbon leading to trisubstituted alkenes stereose- lectively.

Synthesis and characterization of trisubstituted heteropolytungstogermanates containing group 3A elements

Six new compounds, alpha,beta-KaHb[GeW(9)M(3)(H2O)(3)O-37]. xH(2)O(M = Al, Ga, In; a + b = 7) and alpha-K9H5[Ge2W18Ga6(H2O)(3)O-74]. 20H(2)O, were synthesized from the lacunary precursors a and beta-GeW9O3410- and characterized by elemental analysis, spectroscopy and electrochemistry. Tungsten-183 NMR spectra of the title complexes consist of two lines with intensity ratio 2:1 as expected for trisubstituted heteropoly anions. The intensity ratio of alpha-Ga compound is 1:2, which is different from others(a:1). With the help of FAB mass spectrum, we concluded that it is a dimer with D-3h structure in aqueous, and the others exist by monomers with C-3v structures.

(E)-α-Bromovinylselenides as Convenient Precursors for Stereoselective Synthesis of Trisubstituted Alkenes

Based on the different reactivity of selanyl and bromo groups,( E)-α- bromovinylselenides can undergo sequential cross coupling reactions with nucleophiles in the presence of transition metal complexes to form two carbon-carbon bonds in the same olefinic carbon leading to trisubstituted alkenes stereoselectively in good yields.

Conformation of α,α,α′-Trisubstituted Cyclododecanone

Ten α,α,α′-trisubstituted cyclododecanones were synthesized and characterized by elemental analyses, infrared, 1^H NMR and 13^C NMR spectra, and X-ray diffraction. NMR data could not give conformational information clearly, but some of their ring skeleton conformations of cyclododecanone moiety were showed to remain the unchanged [3333]-2-one conformation with little distortion, while the others were changed to the [3324]-2-one conformation in their crystal structures. These are consistent with the results of molecular mechanics calculation with Sybyl 6.9 software and Tripos force field, and semi-empirical quantum calculation with AM 1 method in Gaussian 98 software. Two geminal substituting groups are located at α-corner carbon atom, and the third group is at α-side-exo carbon atom in both conformations. Both [3333]-2-one and [3324]-2-one conformations are present in a dynamic equilibrium in the solution, but only one preferred conformation exists in the crystal solid.

Stereoselective 1,2-Dicarbofunctionalization of Trisubstituted Alkenes by Palladium-Catalyzed Heck/Suzuki or Heck/Sonogashira Domino Sequence

Highly enantioselective and diastereoselective 1,2-diarylation and 1,2-arylalkynylation of trisubstituted alkenes are reported via the palladium-catalyzed Heck/Suzuki or Heck/Sonogashira domino sequence.These alkenes represent an extension of enantioselective dicarbofunctionalization from terminal alkenes to trisubstituted ones based on anionic capture of the secondary alkyl-Pd intermediate.

Syntheses and Structure of Potassium α-and β-Trivanadoenneatungstogermanates

Potassium α-and β-trivanadoenneatungstogermanates were prepared and characterized by means of elemental analysis, IR, 51V and 183W NMR spectra and polarography. The single crystal structure of a-isomer was determined. The final R is 0. 083. The results show that two prepared heteropoly anions have Keggin structure, and a-isomer belongs to A-type and has stronger oxidizing ability than β-isomer.

Preparation，Characterization and Catalytic Activity of Anionic Clay Pillared by GaW＿9Zn＿3

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Synthesis and Properties of Nonatungstotricobaltosilicate Isomers

Introduction Recently substituted-type of heteropolyanions has received much attention from the point of view of their catalysis. Hill, Finke, Neumann reported respectively that transition metal mono-substituted heteropolyanions PW;M, P;W;M and SiW;Ru have an ability to catalyze the epoxidation of olefin. We discovered that trisubstituted Keggin heteropolyanions have this property too. This paper describes the synthesis, properties of α- and β-[SiW;O;Co;（H;O）;];and its catalysis for the epoxidation of olefin by PhIO.