Xigeng Zhou

One-Step Synthesis of Substituted Dihydro- and Tetrahydroisoquinolines by FeCl3·6H2O Catalyzed Intramolecular Friedel−Crafts Reaction of Benzylamino-Substituted Propargylic Alcohols

A mild, versatile, and efficient method for the one-step synthesis of substituted dihydro- and tetrahydroisoquinolines has been developed by the FeCl3.6H2O catalyzed intramolecular allenylation/cyclization reaction of benzylamino-substituted propargylic alcohols, representing the first example of the intramolecular Friedel-Crafts reaction of propargylic alcohols.

Syntheses, Structures, and Reactivities of Homometallic Rare‐Earth‐Metal Multimethyl Methylidene and Oxo Complexes

Unsolvated, trinuclear, homometallic, rare-earth-metal multimethyl methylidene complexes [{(NCN)Ln(μ(2)-CH(3))}(3)(μ(3)-CH(3))(μ(3)-CH(2))] (NCN = L = [PhC{NC(6)H(4)(iPr-2,6)(2)}(2)](-); Ln = Sc (2a), Lu (2b)) have been synthesized by treatment of [(L)Ln{CH(2)C(6)H(4)N(CH(3))(2)-o}(2)] (Ln = Sc (1a), Lu (1b)) with two equivalents of AlMe(3) in toluene at ambient temperature in good yields. Treatment of 1 with three equivalents of AlMe(3) gives the heterometallic trinuclear complexes [(L)Ln(AlMe(4))(2)] (Ln = Sc (3a), Lu (3b)) in good yields. Interestingly, 2 can also be generated by recrystallization of 3 in THF/toluene, thereby indicating that the THF molecule can also induce C-H bond activation of 2. Reaction of 2 with one equivalent of ketones affords the trinuclear homometallic oxo-trimethyl complexes [{(L)Ln(μ(2) -CH(3))}(3) (μ(3)-CH(3))(μ(3)-O)] (Ln = Sc(4a), Lu(4b)) in high yields. Complex 4b reacts with one equivalent of cyclohexanone to give the methyl abstraction product [{(L)Lu(μ(2) -CH(3) )}(3) (μ(3) -OC(6)H(9))(μ(3)-O)] (5b), whereas reaction of 4b with acetophenone forms the insertion product [{(L)Lu(μ(2)-CH(3))}(3){μ(3)-OCPh(CH(3))(2)}(μ(3)-O)] (6b). Complex 4a is inert to ketone under the same conditions. All these new complexes have been characterized by elemental analysis, NMR spectroscopy, and confirmed by X-ray diffraction determination.

FeCl3·6H2O Catalyzed Disproportionation of Allylic Alcohols and Selective Allylic Reduction of Allylic Alcohols and Their Derivatives with Benzyl Alcohol

Iron chloride has been found to be an efficient catalyst for the disproportionation of allylic alcohols, which provides a convenient method for selective transformation of allylic alcohols to alkenes and alpha,beta-unsaturated ketones. Furthermore, this catalytic system is also effective for highly selective allylic reduction of allylic alcohols, allylic ethers, and allylic acetates with benzyl alcohol under neutral and convenient reaction conditions.

Controllable one-step synthesis of spirocycles, polycycles, and di- and tetrahydronaphthalenes from aryl-substituted propargylic alcohols.

A novel, convenient, and efficient method has been developed for selective synthesis of spirocycle, polycycle, and di- and tetrahydronaphthalene systems from aryl-substituted propargylic alcohols by FeCl3- or TsOH-catalyzed multiple activations of unsaturated C-C bonds and C-H bonds.

Insertions into lanthanide-ligand bonds in organolanthanide chemistry

Abstract Insertions of small molecules into lanthanide–ligand bonds have led to a number of new organolanthanide derivatives. Many attractive catalytic transformations are also based on these insertion reactions. The focus of this review concerns these important stoichiometric and catalytic transformations.

Activation of Bis(guanidinate)lanthanide Alkyl and Aryl Complexes on Elemental Sulfur: Synthesis and Characterization of Bis(guanidinate)lanthanide Thiolates and Disulfides

The treatment of [(Me(3)Si)(2)NC(NCy)(2)](2)Ln(mu-Cl)(2)Li(THF)(2) with 1 equiv of BnK (Bn = benzyl) in toluene affords [(Me(3)Si)(2)NC(NCy)(2)](2)LnBn [Ln = Er (1-Er), Y (1-Y)] in good yields. Similarly, [(Me(3)Si)(2)NC(NCy)(2)](2)Ln(t)Bu [Ln = Er (2-Er), Yb (2-Yb)] are obtained in satisfactory yields by the reaction of [(Me(3)Si)(2)NC(NCy)(2)](2)Ln(mu-Cl)(2)Li(THF)(2) with (t)BuLi in hexane. 1 reacts with 1/8 equiv of S(8) in toluene to form the sulfur insertion products {[(Me(3)Si)(2)NC(NCy)(2)](2)Ln(mu-SBn)}(2) [Ln = Er (3-Er), Y (3-Y)], while the reaction of 2 with elemental sulfur under the same conditions affords the oxidation products {[(Me(3)Si)(2)NC(NCy)(2)](2)Ln}(2)(mu-eta(2):eta(2)-S(2)) [Ln = Er (4-Er), Yb (4-Yb)] regardless of the equivalency of S(8) employed. Disulfide complexes 4 can also be obtained by the reaction of 3 with (1)/(4) equiv of S(8). Furthermore, the treatment of [(Me(3)Si)(2)NC(NCy)(2)](2)Ln(mu-Cl)(2)Li(THF)(2) with 1 equiv of (n)BuLi in hexane, followed by reaction with (1)/(8) equiv of S(8), affords the dinuclear thiolate complexes {[(Me(3)Si)(2)NC(NCy)(2)](2)Ln(mu-S(n)Bu)}(2) [Ln = Y (5-Y), Er (5-Er)] in good yields. However, under the same conditions, [(Me(3)Si)(2)NC(NCy)(2)](2)Yb(mu-Cl)(2)Li(THF)(2) reacts with (n)BuLi and S(8) to give {[(Me(3)Si)(2)NC(NCy)(2)](2)Yb}(2)(mu-eta(2):eta(2)-S(2)) (4-Yb) as the main metal-containing product. [(Me(3)Si)(2)NC(NCy)(2)](2)LnPh (generated in situ from [(Me(3)Si)(2)NC(NCy)(2)](2)Ln(mu-Cl)(2)Li(THF)(2) and PhLi) also undergoes sulfur insertion, affording {[(Me(3)Si)(2)NC(NCy)(2)](2)Ln(mu-SPh)}(2) [Ln = Er (6-Er), Yb (6-Yb)] in good yields. All of the complexes were characterized by spectroscopic and elemental analyses. The structures of all of these compounds, except 3-Y, are also determined by single-crystal X-ray diffraction analysis. Surprisingly, 3, 5, and 6 bear the same space group and very similar cell parameters, despite the different thiolate ligands.

Insertion of carbodiimide into the LnN σ-bond of organolanthanide complexes. Synthesis and characterization of organolanthanide guanidinates (C5H5)2Ln[iPrNC(NiPr2)∴NiPr] (Ln=Yb, Dy, Gd)

Abstract The synthesis and structures of three new lanthanide complexes incorporating tetra-substituted guanidinate ligand [iPrN∴C(NiPr2)∴NiPr] are described. Treatment of Cp2LnNiPr2(THF) (Ln=Yb, Dy, Gd) with N,N′-di-isopropyl-carbodiimide results in mono-insertion of carbodiimide into the LnN σ-bond to yield Cp2Ln[iPrN∴C(NiPr2)∴NiPr] (Ln=Yb(1), Dy(2), Gd(3)), providing an efficient method for the synthesis of organolanthanide guanidinate complexes. It was found that an excess of N,N′-di-isopropyl-carbodiimide did not affect the nature of the final product. Complexes 1–3 were characterized by elemental analysis, IR and mass spectroscopies. Complexes 1 and 2 were determined by the X-ray single crystal diffraction analysis.

Synthesis, structures, and reactivity of yttrium alkyl and alkynyl complexes with mixed Tp(Me2)/Cp ligands.

The structurally characterized Tp(Me2)-supported rare earth metal monoalkyl complex (Tp(Me2))CpYCH(2)Ph(THF) (1) was synthesized via the salt-metathesis reaction of (Tp(Me2))CpYCl(THF) with KCH(2)Ph in THF at room temperature. Treatment of 1 with 1 equiv of PhC≡CH under the same conditions afforded the corresponding alkynyl complex (Tp(Me2))CpYC≡CPh(THF) (2). Complex 1 exhibits high activity toward carbodiimides, isocyanate, isothiocyanate, and CS(2); treatment of 1 with such substrates led to the formation of a series of the corresponding Y-C(benzyl) σ-bond insertion products (Tp(Me2))CpY[(RN)(2)CCH(2)Ph] (R = (i)Pr(3a), Cy(3b), 2,6-(i)Pr-C(6)H(3)(3c)), (Tp(Me2))CpY[SC(CH(2)Ph)NPh] (4), (Tp(Me2))CpY[OC(CH(2)Ph)NPh] (5), and (Tp(Me2))CpY(S(2)CCH(2)Ph) (6) in 40-70% isolated yields. Carbodiimides and isothiocyanate can also insert into the Y-C(alkynyl) σ bond of 2 to yield complexes (Tp(Me2))CpY[(RN)(2)CC≡CPh] (R = (i)Pr(7a), Cy(7b)) and (Tp(Me2))CpY[SC(C≡CPh)NPh] (9). Further investigation results indicated that 1 can effectively catalyze the cross-coupling reactions of phenylacetylene with carbodiimides. However, treatment of o-allylaniline with a catalytic amount of 1 gave only the benzyl abstraction product (Tp(Me2))CpY(NHC(6)H(4)CH(2)CH═CH(2)-o)(THF) (10), without observation of the expected organic hydroamination/cyclization product. All of these new complexes were characterized by elemental analysis and spectroscopic properties, and their solid-state structures were also confirmed by single-crystal X-ray diffraction analysis.

A novel bonding mode of tetrazolate ligand to a metal: synthesis and structural characterization of 5-phenyltetrazolate organolanthanide complexes: [{(C5H4Me)(C5H5)LnTz}2][{(C5H4Me)2LnTz}2] (Ln=Dy, Gd) and [(C5H4Me)2LnTz)]2 (Ln=Yb, Er)

Reaction of (C 5 H 4 Me) 3 Ln and TzH (5-phenyl-1H-tetrazole) in THF affords complexes [(C 5 H 4 Me) 2 LnTz] 2 [Ln=Yb ( 1 ), Er ( 2 )]. 1 crystallized in the space group C 2/ c , with unit cell dimensions a =25.596(2), b =8.342(1), c =21.573(2) A, β =129.322(9)°. V =3563.5(8) A 3 and Z =8 for D c =1.776 g cm −3 . Least-squares refinement of the model based on 2700 reflections converged to a final R =0.031. The molecule is centrosymmetric dimer in which each ytterbium atom is coordinated by two methylcyclopentadienyl groups and three nitrogen atoms of the bridging Tz ligands to form a distorted trigonal-bipyramidal geometry. When there is a small amount of (C 5 H 4 Me) 2 Ln(C 5 H 5 ) in (C 5 H 4 Me) 3 Ln, the 1:1 complexes [{(C 5 H 4 Me)(C 5 H 5 )LnTz} 2 ][{(C 5 H 4 Me) 2 LnTz} 2 ] (Ln=Dy ( 3 ), Gd ( 4 )) were obtained in crystalline form. 3 and 4 crystallize as isomorphous crystals of space group P 1 with the following unit cell parameters ( 3 / 4 ): a =9.374(2)/9.420(4), b =13.048(2)/13.215(4), c =16.542(4)/16.677(5) A, a =86.95(2)/87.24(2), β =74.61(1)/74.50(3), γ =77.31(1)/77.08(3)°, Y =1903(1)/1950(1) A 3 , Z =2, D c =1.602/1.545 g cm −3 , R =0.046/0.051. Crystallographic data for 3 and 4 show that there are two disconnected structural units [(C 5 H 4 Me)(C 5 H 5 )Ln( μ - η 1 : η 2 -Tz)] 2 and [(C 5 H 4 Me) 2 Ln( μ - η 1 : η 2 -Tz)] 2 , crystallizing in one asymmetrical unit, each of which is tetrazolate-bridged dimer and has an inversion center. The bridging unit Ln 2 N 6 is planar. All three structures reveal an unusual bonding mode of the tetrazolate ligand, in which the tetrazolate group acts as both a bridging and chelating ligand, with the nitrogen atoms at 1, 2 and 3-position taking part in bonding.

γ-Deprotonation of Anionic Bis(trimethylsilyl)amidolanthanide Complexes with a Countered [(TpMe2)2Ln]+Cation

Tp(Me2)LnCl(2) (1) reacts with 2 equiv of KN(SiMe(3))(2) in tetrahydrofuran at room temperature to yield the ligand redistribution/gamma-deprotonation products [(Tp(Me2))(2)Ln](+)[((Me(3)Si)(2)N)(2)Ln(CH(2))SiMe(2)N(SiMe(3))](-) [Ln = Er (2), Y (3)]. Complex 2 can also be obtained by reacting [(Me(3)Si)(2)N](2)ErCl with KTp(Me2). However, 1 reacts with 1.5 and 1 equiv of KN(SiMe(3))(2) to yield [(Tp(Me2))(2)Er](+)[((Me(3)Si)(2)N)(3)ErCl](-) (4) and [(Tp(Me2))(2)Er](+){[(Me(3)Si)(2)N)Tp(Me2)ErCl](2)(mu-Cl)(2)K}(-) (5), respectively. Furthermore, it is found that 2 reacts with 2 equiv of CyN=C=NCy (Cy = cyclohexyl) to give the tandem HN(SiMe(3))(2) elimination and Ln-C insertion product (Tp(Me2))Er[(CyN)(2)CCH(2)SiMe(2)N(SiMe(3))] (6) in 71% isolated yield. The results reveal that the gamma-deprotonation degree of advancement increases with an increase of the steric hindrance around the central metal ion. All new complexes have been characterized by elemental analysis and spectroscopic properties, and their solid-state structures have also been determined through single-crystal X-ray diffraction analysis.