Nickel-catalyzed regio- and stereoselective hydrophosphinylation of internal ynamides with H-phosphinates

A method for the catalytic hydrophosphinylation of internal ynamides with H-phosphinates has been developed for the first time. The protocol employing the catalyst generated from NiBr₂ and PPh₃ could be applied to several types of ynamides and H-phosphinates, affording (E)-β-aminovinylphosphinates in a highly regio- and stereoselective manner.     

An efficient construction of a C3-symmetric macrocycle by head to tail cyclotrimerization of an unsymmetrical diene via a sequence of highly regio- and stereoselective metathesis reactions

A sequence of highly regio- and stereoselective intermolecular metatheses followed by ring-closing metathesis of an 1-allyl-3-(3-butenyl)cyclohexanol led to a C₃-symmetric head to tail cyclic trimer; a 24-membered macrocycle containing three inward directed hydroxyl groups creating a hydrophilic cavity.     

Novel bis[(E)-1-(halomethyl)-2-chlorovinyl] chalcogenides as starting materials for the efficient synthesis of bis(chloromethylidene)-1,4-dichalcogenanes

An efficient synthesis of novel bis[(E)-1-(halomethyl)-2-chlorovinyl] sulfides and selenides via regio- and stereoselective electrophilic addition of SCl₂ and SeCl₂ to propargyl halides has been developed. The bis(2-chlorovinyl) chalcogenides prepared represent reagents for the synthesis of chalcogen-containing heterocycles and have been used for the synthesis of novel bis(E-chloromethylidene) derivatives of 1,4-dichalcogenanes with various combinations of sulfur and selenium atoms in the ring.     

Regio- and stereoselective synthesis of highly functionalized vinyl ethers via coiodination of acetylenic ketones

A Cu(OTf)₂-catalyzed highly regio- and stereoselective coiodination of acetylenic ketones was reported, providing a mild and convenient method for the synthesis of (Z)-β-carbonyl-β-iodoenol ethers in good yields.     

Regioselective alkenylation of imidazoles by nickel/Lewis acid catalysis

Nickel/Lewis acid binary catalysis is found effective to direct regioselective alkenylation of imidazoles through C-H bond activation and stereoselective insertion of alkynes. Use of P(t-Bu)₃ as a ligand allows exclusive regioselective C(2)-alkenylation, while PCyp₃ is found effective for C(5)-alkenylation of C(2)-substituted imidazoles. The reaction demonstrates a broad scope of imidazoles and internal alkynes to give trisubstituted ethenes highly regio- and stereoselectively in modest to good yields.     

Synthesis of cis-1,2-dichlorovinylsulfones via Fe-catalyzed regio- and stereoselective addition of sulfonyl chlorides to aromatic chloroalkynes

An iron-catalyzed regio- and stereoselective chlorosulfonylation of aryl chloroalkynes has been described, producing cis-1,2-dichlorovinylsulfones in satisfactory yields with good to excellent stereoselectivity (Z/E up to 95:5). A variety of functional groups such as F, NO₂, Cl, Br, OMe, and t-Bu are found to be compatible under the reaction conditions.     

Fluoride anion-induced intramolecular cyclopropanation of allylsilanes

The reaction of cyclopentenylsilane derivatives with n-Bu₄NF in THF at rt was shown to proceed with the regio- and stereoselective formation of the corresponding bicyclo[3.1.0]hex-2-ene derivatives.     

Toward a modular, bidirectional synthesis of (−)-mucocin

A convergent stereoselective synthesis of the C13-C34 fragment of (−)-mucocin is described. The salient features include (a) the bidirectional synthesis of the C-2 symmetric C13-C21 subunit, (b) regio- and stereoselective preparation of a 1,3-diol derivative from a diene activated by NBS via intramolecular nucleophilic sulfinyl group participation, (c) utilizing the self-metathesis reaction to prepare a functionalized C10 alkene, and (d) regio- and stereoselective intermolecular epoxide opening to construct the ether bond between C20 and C24. An organocatalytic α-hydoxylation has been employed to create the C4 stereogenic center of C1-C12 subunit. Attempted union of the two subunits utilizing the B-alkyl Suzuki coupling did not succeed.     

Versatile use of acid-catalyzed ring-opening of β-aziridinyl-α,β-enoates to stereoselective synthesis of peptidomimetics

Treatment of N-arylsulfonylaziridines bearing α,β-unsaturated esters with alcohols, thiols or weak acids such as AcOH in the presence of catalytic amount of Lewis acids affords regio- and stereoselectively ring-opened products, such as δ-aminated γ-alkoxy-(alkylthio or acetoxy)-α,β-enoates. In addition, the regio- and stereoselective ring-opening reactions can be performed on solid supports and applied to stereoselective synthesis of (E)-alkene dipeptide isosteres.     

Ionic liquid media resulted in more efficient regio- and stereoselective aminohalogenation of cinnamic esters

The ionic liquid, butylmethylimidazolium tetrafluoroborate ([Bmim][BF4]), was found to be superior to classical organic solvents for the metal catalyzed regio- and stereoselective aminohalogenation of cinnamic esters. The aminohalogenation reaction of cinnamic esters with p-TsNCl₂ proceeded at a faster rate (within 12 h) in the presence of a reduced amount of catalyst (CuOTf, 6.0 mol %). Good yields (76-82%) and excellent regio- and stereoselectivity (one isomer) were achieved for eight examples.     

Highly stereoselective synthesis of 6-perfluoroalkyl-6-fluoroalka-2,3,5-(Z)-trienols through carbometallation-elimination of 5-perfluoroalkyl-substituted 4(E)-alken-2-ynols with Grignard reagents

A highly regio- and stereoselective sequential carbometallation and Z-selective β-elimination reaction of 5-perfluoroalkyl-4(E)-en-2-ynols with Grignard reagents in Et₂O has been developed to afford various 6-perfluoroalkyl-6-fluoroalka-2,3,5(Z)-trienols in good to excellent yields. Primary or secondary alkyl or aryl Grignard reagents may be used to introduce the R² group to the 2-position of the starting materials referring to the hydroxyl group. A mechanism for this transformation has been proposed.     

Highly regio- and diastereoselective three-component reaction of acyclic/cyclic donor–acceptor carbenoids for the synthesis of angularly fused furocoumarins and spirooxindolylfurocoumarins

A highly regio- and stereoselective method has been developed for the synthesis of spiro[furo[3,4-c]chromene-1,3′-indoline]-2′,4(9bH)-dione derivatives via a three component reaction of cyclic diazoamide and aldehyde with methyl 2-oxo-2H-chromene-3-carboxylate, 3-acetyl-2H-chromen-2-one and 3-benzoyl-2H-chromen-2-one using 3 mol % of Rh₂(OAc)₄. Similarly, acyclic diazoesters also undergo smooth coupling with carbonyl compounds and 3-substituted coumarin in the presence of 1 mol % of Rh₂(OAc)₄ to afford a novel series of tetrahydro-1H-furo[3,4-c]chromene-1-carboxylates in 78–88% yield with high regio- and stereo-selectivity for the first time.     

Chemo-, regio- and stereoselective addition of triorganoindium reagents to acetates of Baylis-Hillman adducts: a new strategy for the synthesis of (E)- and (Z)-trisubstituted alkenes

The addition of several trialkyl or triarylindium reagents to the acetates of Baylis-Hillman adducts proceeds readily under the catalysis of copper and palladium derivatives. The reactions of trialkylindiums are catalyzed efficiently by CuI whereas additions of triarylindiums produce better results with Pd(PPh₃)₄. The reactions with 3-acetoxy-2-methylenealkanoates provide (E)-alkenes, whereas similar reactions with 3-acetoxy-2-methylenealkanenitriles lead to (Z)-alkenes. All the reactions are highly regio- and stereoselective and high yielding.     

An efficient route to regioselective opening of N-tosylaziridines with zinc(II) halides

An efficient route for the regio- and stereoselective ring opening of N-tosylaziridines with zinc dihalides (ZnX₂, X = Cl, Br, I) is described. Depending on the solvent and Zn(II) halide, β-halo amines or imidazolines are obtained selectively in good to excellent yields.     

Spirane-bridged ansa η-cyclopentadienyl-η-fluorenyl-zirconocene precatalysts

Synthesis of rigid ansa-zirconocene precatalyst systems with a C₂-bridge embedded in a spirane scaffold is described. Fulvenes were key intermediates in regio- and stereoselective preparation of the appropriate spirane ligands. Substitution in the cyclopentadienyl group in the ligand was effected by fulvene methodology. The zirconocenes were active precatalysts for the polymerisation of propene when activated with MAO. The structure of the parent zirconocene dichloride has been verified by X-ray crystal analysis.     

Synthesis of enantiopure 2-amino-1-phenyl and 2-amino-2-phenyl ethanols using enantioselective enzymatic epoxidation and regio- and diastereoselective chemical aminolysis

Several enantiopure 1,2-amino alcohols have been prepared by combining a stereoselective enzymatic epoxidation of styrenes with regio- and stereoselective chemical reactions. An interesting reactivity has been noted concerning the reaction of epoxides and NH₃ under microwave activation.     

Silver-promoted trans-hydrofluorination of ynamides: a regio- and stereoselective approach to (Z)-α-fluoroenamides

A highly regio- and stereoselective trans-hydrofluorination of N-sulfonyl ynamides has been realized with AgF as the fluorination reagent, affording (Z)-α-fluoroenamides in good to excellent yields. The reaction proceeds under mild reaction conditions and shows good functional group compatibility.     

Stereoselective synthesis of a new methyl-substituted inositol derivative

The stereoselective synthesis of methyl-substituted inositol derivative is described. Diene diacetate which is a key compound was first prepared via three steps starting from 2-methyl-p-benzoquinone. Osmium-catalyzed regio- and stereoselective dihydroxylation of diene diacetate afforded cis-diol diasetate, which then produced tetra acetate via acetylation with Ac₂O-pyridine. Oxidation and acetylation of the other alkene moiety in the compound gave a hexaacetate compound stereoselectively. Finally, the acetate groups were removed by NH₃ leading to formation of the desired new methyl-substituted inositol derivative having a muco-inositol-type stereochemical pattern in the six-membered ring. Spectroscopic methods were used for characterization of all synthesized compounds.     

Copper (II)-catalyzed regio- and stereoselective addition of H/P(O)R2 to alkynes

Cu(acac)₂ is the new universal catalyst for β-E regio- and stereoselective syn-addition of the H–P(O)-bond of diphenylphosphine oxide, H-phosphinates, dialkylphosphites to various alkynes in the synthesis of P(O)-containing alkenes. Without additives and ligands Cu(II)-compounds showed better results than CuI or Ni(acac)₂. The catalytic system developed is tolerant to typical organic functional groups present in the alkynes and to the nature of different substituents in the H–P(O)-compounds.     

Lewis acid catalyzed intramolecular halo-arylation of tethered alkenes using N-halosuccinimide (NXS) as the halogen source: a general method for the synthesis of chromanones, chromans, quinolones, tetrahydroquinolines and tetralins

Lewis acid catalyzed intramolecular halo-arylation of tethered alkenes was performed using N-halosuccinimide (NXS) as the halogen source. Among the Lewis acids investigated, Sm(OTf)₃ was found to be the best catalyst. This catalytic process provides a general method for the regio- and stereoselective synthesis of annulated arene heterocycles and carbocycles such as 2-chromanones, chromans, 2-quinolones, tetrahydroquinolines and tetralins possessing a halo-functionality.