A Facile Generation of a Cyclopropylzinc Compound from an Alkenylzinc Derivative and Its Reaction with Electrophiles

The one-pot synthesis of cyclopropyl compounds from 1-alkynes has been achieved by direct cyclopropanation of a 1-alkenylzinc species upon treatment with iodomethylzinc and trapping of the cyclopropylzinc intermediate with allyl bromide in the presence of CuCN⋅2 LiCl (see reaction scheme). This method proceeds under mild conditions and in good yield.     

Synthesis of heterocycles from acetylenic carbonyl compounds and dinucleophilic reagents (review)

The literature on reactions of sulfur, oxygen, and nitrogen-containing dinucleophilic reagents with acetylenic carbonyl compounds is reviewed. The mechanisms of some reactions are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 291–304, March, 1987.     

A new protocol for synthesis of bifunctional alkynyl[vinyl or (E)-alkenyl]substituted organosilicon compounds

A new efficient route for selective synthesis of various, novel alkynyl(vinyl)substituted silicon (6) and alkynyl[(E)-alkenyl]substituted silicon compounds (9) via silylative coupling of alkynes and their products catalyzed by ruthenium(+2) complexes is described. The tandem procedure facilitates the formation of 9 synthesized in a high yield and stereoselectivity by a sequential silylative coupling of terminal alkynes with divinylsubstituted silicon compounds followed by silylative coupling reaction of 6 with styrenes in the presence of ruthenium hydride complexes ([RuHCl(CO)(PR₃)_3−n]; R = Cy (n = 1), i-Pr (n = 1), Ph (n = 0)).     

Intramolecular coupling of acetylenic groups of bis(alkynyl)phosphanes and silanes mediated by benzynezirconocene: a route to new mono- and tricyclic heterocycles

Benzo-zirconacyclohexadiene-phospha or silacyclobutene fused ring systems are easily prepared via a benzynezirconocene intermediate by means of thermolysis of Cp₂ZrPh₂ in the presence of bis(alkynyl)phosphanes or silanes. These polyunsaturated systems are the source of a variety of new mono- or tricyclic heterocycles incorporating either one or two heteroatoms.     

Unexpected synthesis of aziridines under Cu(I) catalyzed Kinugasa conditions assisted by microwave irradiation

Cu(I)-catalyzed 1,3-dipolar cycloaddition between chiral nitrone and terminal alkynes under microwave irradiation afforded a series of enantiopure aziridines with the creation of two contiguous stereogenic centers.     

Optical properties of binuclear zinc (II) macrocyclic complexes derived from 4-methyl-2,6-diformylphenol and 1,2-diaminobenzene

In this work, we present the synthesis and optical study of the binuclear zinc(II) macrocyclic complexes, derived from 4-methyl-2,6-diformylphenol and 1,2-diaminobenzene (H₂L). Two zinc macrocyclic complexes with different anions were prepared and characterized: [Zn₂LCl₂]·H₂O (1) and [Zn₂L](NO₃)₂ (2).     

Synthesis and characterization of poly(esters) derived from diacids and diphenols containing silicon and germanium

Poly(esters) containing two heteroatoms, Si or Ge, in the main chain, derived from diphenols bis(4-hydroxyphenyl)-dimethyl-germane, bis(4-hydroxyphenyl)-diphenyl-germane, bis(4-hydroxyphenyl)-dimethyl-silane and bis(4-hydroxyphenyl)-diphenyl-silane, and the acid dichlorides bis(4-chloroformyl-phenyl)-dimethyl-germane, bis(4-chloroformyl-phenyl)-diphenyl-germane, bis(4-chloroformyl-phenyl)-dimethyl-silane and bis(4-chloroformyl-phenyl)-diphenyl-silane, were synthesized under phase transfer conditions using two phase transfer catalysts, and characterized by spectroscopic methods. This technique showed low effectivity for the synthesis of these kinds of polymers, showing a low increase of the yields and η_inh values in comparison with the interphasial process. In these experimental conditions there were no important differences neither in the studied parameters between the monomers with Si or Ge, nor between the catalysts.     

Synthesis and spectroscopic studies of nickel(II) chalcogenolates derived from 1,2-diarylchalcogenolato-o-xylene

Nickel(II) chalcogenolate complexes [Ni(L-L)₂(dppe) Cl₂] (1, 2) have been prepared in high yields by reacting 1,2-diarylchalcogenolato-o-xylene, o-C₆H₄(CH₂EAr)₂ (E = Se or Te; Ar = Ph, C₆H₄OMe-4 and C₆H₄OEt-4), generated in situ, with Ni(dppe)Cl₂ [dppe = 1,2-bis(diphenylphosphino)ethane] in benzene. The structures were established by elemental analyses, molar conductance, i.r. and Raman, electronic ¹H- and ³¹P-n.m.r. and mass spectral data. The analytical and spectroscopic data are consistent with an octahedral geometry around nickel in (1) and (2). The ³¹P-n.m.r. spectra indicate their cis configuration in solution. This revised version was published online in June 2006 with corrections to the Cover Date.     

Highly regioselective ring opening of epoxides and aziridines using (bromodimethyl)sulfonium bromide

Epoxides and aziridines undergo ring opening efficiently with (bromodimethyl)sulfonium bromide at room temperature to form the corresponding β-bromohydrins and β-bromoamines, respectively. The conversions are highly regioselective and afford the products in excellent yields within a short period of time.     

Cerium(III) chloride promoted highly regioselective ring opening of epoxides and aziridines using NaN(3) in acetonitrile: a facile synthesis of 1,2-azidoalcohols and 1,2-azidoamines

A convenient and efficient synthesis of 1,2-azidoalcohols and 1,2-azidoamines has been achieved by ring opening of epoxides and aziridines using cerium(III) chloride and sodium azide in acetonitrile. The reaction is highly regioselective and afforded the corresponding products in good to excellent yields under mild and neutral reaction conditions. The method is very rapid and equally compatible for both epoxides and aziridines.     

Zinc(0)/dimethylformamide-mediated synthesis of symmetrical carboxylic anhydrides from acid chlorides

The high yielding synthesis of symmetrical carboxylic anhydrides from acid chlorides mediated by zinc dust in the presence of dimethylformamide is presented. A mechanism involving the reductive insertion of zinc(0) into the C-Cl bond of a Vilsmeier-type iminium intermediate as the crucial step is also proposed.     

The structure and racemization of 1,2-bis(pentaphenylphenyl)benzene

1,2-Bis(pentaphenylphenyl)benzene (2) was synthesized by the cycloaddition of 1,2-bis(phenylethynyl)benzene and tetracyclone. Its X-ray structure was determined, and the molecule adopts a C₂-symmetric conformation in the crystal. Monomethoxy and dimethoxy derivatives of compound 2 were also prepared, and dynamic NMR studies of these compounds yielded a free energy of activation for racemization (ΔG³_rac) of 20.3?kcal/mol at 423?K. The results are compared with estimates of ΔG³_rac for 2 by various DFT methods.     

Synthesis of carbosilane dendrons and dendrimers derived from 1,3,5-trihydroxybenzene

Several carbosilane wedges of generations 1-3 have been synthesized, following the divergent method, containing at the focal point a C-Br bond and as peripheral functional groups SiMeCl₂, SiMe(C₃H₅)₂, SiMe₂Cl, SiMe₂H, and ester units SiMe₂{(C₃H₆)N(C₂H₄CO₂Me)₂}. The dendrons functionalized with SiMe(C₃H₅)₂ and SiMe₂{(C₃H₆)N(C₂H₄CO₂Me)₂} groups were used to synthesize spherical dendrimers derived from 1,3,5-(HO)₃C₆H₃, leaving the outer groups unchanged. The allyl dendrimers thus obtained were used as precursors to prepare new dendrimers functionalized with SiMeCl₂, SiMe₂Cl, SiMe₂H, amine units SiMe₂{(C₃H₆)NH₂} and also ester units SiMe₂{(C₃H₆)N(C₂H₄CO₂Me)₂}.     

Hydrolysis of epoxides and aziridines catalyzed by polymer-supported quarternary ammonium bisulfate

Macroporous resin （D201）-supported quartemary ammonium bisulfate （D201-HSO4） was prepared and effectively used in catalyzing the hydrolysis of epoxides or aziridines under mild and non-metal conditions to give the corresponding 1,2-diols and β-amino alcohols in high yields. The catalyst was facilely prepared and recyclable.     

Synthesis and characterization of new aromatic polyesters and polyethers derived from 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethylene

New polyarylates and aromatic polyethers were synthesized from 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethylene, and aromatic dicarboxylic acid chlorides and aromatic dihalides, respectively. The polyarylates having inherent viscosities of 0.28–1.05 dL/g were synthesized by either the two-phase method or the high-temperature solution method. All the polymers were easily soluble in N-methyl-2-pyrrolidone, N,N-dimethylformamide, pyridine, m-cresol, 1,4-dioxane, and 1,1,2,2-tetrachloroethane. They have glass transition temperatures in the range of 217–250°C and showed no weight loss below 315°C in both air and nitrogen atmospheres. Aromatic polyethers with inherent viscosities of 0.85–1.21 dL/g were obtained by the polycondensation of 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethylene and aromatic difluorides in the presence of potassium carbonate. These polymers having glass transion temperatures of 193–220°C were also soluble in the aforementioned solvents and stable up to around 350deg;C in both atmospheres. © 1994 John Wiley & Sons, Inc.     

Synthesis of vicinal (alkylamino)alkynylcyclopropanes from geminal alkynyl(chloro)cyclopropanes

New N-Boc-alkyl(2-alkynylcyclopropyl)amines were synthesized from 1-alkynyl-1-chlorocyclopropanes and N-Boc- alkylamines under the action of Bu^tOK in DMSO, the intermediates having been the corresponding conjugated alkynylcyclopropenes. The Boc-derivatives can be converted into free secondary 2-alkynylcyclopropylamines, as well as β-lithiated with subsequent alkylation.     

Preparation of α-silyl- or α,α-bis(silyl)-substituted alkylcopper reagents and their synthetic use

Treatment of chlorobis(methyldiphenylsilyl)methyllithium with various alkyl and aryl Grignard reagents and CuCN·2LiCl afforded 1,1-disilylalkylcopper species. The aerobic oxidation of the resulting copper reagents provided a variety of acylsilanes in good yields. Meanwhile, treatment of dichloro(methyldiphenylsilyl)methyllithum with Bu₂CuLi·LiCN provided 1-cyano-1-silylalkylcopper species via consecutive double 1,2-migration of alkyl and cyano groups.     

Synthesis,spectra and redox behaviour of copper(II) chalcogenolates derived from 1,2-diarylchalcogenolato-o-xylene

Copper(II) chalcogenolate complexes [Cu(L-L)2Cl2]middot 2H2O (1,2) have been synthesized from the reaction between1,2-diarylchalcogenolato-o-xylene, o-C6H4(CH2EAr)2, (E=Te or Se; Ar=Ph, C6H4Me-4, C6H4OMe-4 and C6H4OEt-4) generated in situ, and CuCl2middot 2H2O in PhH-EtOH in high yields. These complexes are monomeric, non-electrolyte and paramagnetic, indicating a distorted square-planar geometry around the CuII, which is supported by i.r., electronic, e.s.r. and magnetic susceptibility measurements. Polycrystalline and frozen solutions of the compounds have axial e.s.r. signals and the principal components of the g tensors are reported. Electrochemical studies of (1) and (2) using cyclic voltammetry indicate irreversible cathodic peaks in the 0.55–0.78V versus Ag/AgCl range, corresponding to reduction of CuII to CuI and a diffusion-controlled electrode process. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis and structural elucidation of solvent-free and solvated lithium dimethyl (HMDS) zincates

Using a co-complexation methodology the unsolvated lithium zincate [LiZn(HMDS)Me2] ( 4, HMDS = 1,1,1,3,3,3-hexamethyldisilazide) was prepared by reaction of an equimolar amount of LiHMDS with Me2Zn in a non-polar toluene-hexane solvent mixture. X-Ray crystallographic studies reveal that the asymmetric unit of 4 has a dinuclear arrangement, based on a planar LiNZnC four-membered ring. As a result of intermolecular interactions between the lithium centre of one asymmetric unit and a terminal methyl group of another, 4 presents a polymeric chain array in the solid state. DFT calculations revealed that the formation of the polymer is the driving force for the success of co-complexation of LiHMDS and Me2Zn to yield the unsolvated zincate 4. The reaction of 4 with PMDETA (N,N,N,N,N-pentamethyldiethylenetriamine) afforded the new solvated zincate [(PMDETA)Li(mu-Me)Zn(HMDS)Me] ( 5). X-Ray crystallographic studies show that the asymmetric unit of 5 consists of an open, dinuclear LiCZnC arrangement rather than a closed cyclic one, in which the HMDS ligand unusually occupies a terminal position on Zn. DFT computational studies showed that the structure found for 5 was energetically preferred to the expected HMDS-bridging isomer due to the steric hindrance imposed by the tridentate PMDETA ligand. The reaction of 4 with the neutral nitrogen donors 4-tert-butylpyridine and tert-butylcyanide afforded the homometallic compounds [(tBu-pyr)Li(HMDS)] ( 6) and [(tBuCN)Li(HMDS)] ( 7) respectively as a result of disproportionation reactions. Compounds 6 and 7 were characterized by NMR (1H, 13C and 7Li) spectroscopy.     

Studies on quinones. Part 40: Synthesis and cytotoxicity evaluation of anthraquinone epoxides and isomerization products

Aerobic oxidation of 1,4,4a,10a-tetrahydro-1,4-alkano-5,10-anthraquinones and thiophene-analogues in dichloromethane-DBU yielded the corresponding dihydroalkanoquinones which, depending on their structures, react with in situ generated hydroperoxide anion to give quinone epoxides and/or hydroperoxides. The calcium hydroxide-induced rearrangement of quinone epoxides yielded furan-containing angular quinones. The cytotoxic activities of quinone epoxides and their isomerization products were evaluated in vitro against normal human lung fibroblasts (MRC-5) and human cancer gastric epithelial cells (AGS).