Zirconocene Chloride Research Articles

The Immobilized Zirconocene Chloride on Magnetite‐reduced Graphene Oxide: A Highly Efficient and Reusable Heterogeneous Nanocatalyst for One‐pot Three‐component Synthesis of Tetrahydrobenzo[b]pyrans and Dihydropyrano[3,2‐c]chromenes

AbstractThe present paper describes the synthesis and characterization of the functionalized magnetite reduced graphene oxide (rGO@Fe3O4) with zirconocene dichloride as rGO@Fe3O4@ZrCp2Cl2. The prepared magnetic nanomaterial was characterized by Fourier‐transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), inductively coupled plasma optical emission spectroscopy (ICP‐OES) and mass spectrometry (MS). This new heterogeneous nanocatalyst showed the perfect catalytic activity towards synthesis of tetrahydrobenzo[b]pyran and Dihydropyrano[3,2‐c]chromenes derivatives through multicomponent reaction of dimedone or 4‐hydroxycoumarin, malononitrile and aromatic aldehydes in polyethylene glycol 400 (PEG‐400) at 100 °C. The influence of the amount of nanocatalyst, varying temperature of the reaction and the kind of solvent on the rate of condensation reaction was investigated. Recovery and reusability of the applied nanocatalyst was examined for five consecutive cycles without the significant loss of its catalytic activity.

From Flask to Mill: Reductive Functionalization of Fluoroacetamides as a Case Study for Transferring Solvent-Based Reactions to the Solid State

The development of sustainable methods is a central focus of modern organic synthesis and has applications in various areas of the chemical industry. Mechanochemistry is a highly desirable green synthetic method as it departs from traditional solution-based reactions and their concurrent generation of waste solvent. Here, we report results of the adaptation of a solution-based method for the reductive functionalization of fluoroacetamides to a mechanochemical protocol as a case study. This greener solid-state, one-pot strategy is based on the partial reduction of amides by an in situ mechanochemically generated zirconocene chloride hydride (Schwartz’s reagent) and tandem nucleophilic addition of indole to afford high-value functionalized fluorinated amines in moderate to good yields. In addition to it being the first time this reductant has been mechanochemically generated, the sustainable approach was complemented by operationally simple purification by an acidic resin. Significant improvements in green metrics (E factor and EcoScale) were observed by this adaptation of the methodology.

Zirconium Catalyzed Transformations Using Organoboron

AbstractOrganoboron compounds have extreme potential for organic synthesis. Ready functionalization of organoboron intrigued people to develop various protocols for their synthesis. Over the last several decades, there has been a substantial development in synthesizing new organoboron compounds using transition metals. Among various transition metals, zirconium has also been found to catalyze diverse reactions of organoboron. The zirconium chemistry has become more popular with the development of zirconium metallocenes, particularly bis(cyclopentadienyl)zirconocene chloride hydride, the well‐known Schwartz reagent. These zirconium metallocenes possess a significant role in hydrozirconation, hydroboration, hydrogenation, carbozirconation, and a promising tri‐n‐butyl tin hydride alternative. This minireview focuses on the various transformations of organoboron employing zirconium catalysts that have been developed so far.

The Immobilized Zirconocene Chloride on Magnetite-Reduced Graphene Oxide: A Highly Efficient and Reusable Heterogeneous Nanocatalyst for One-Pot Three-Component Synthesis of Tetrahydrobenzo[B]Pyrans and Dihydropyrano[3,2-C]Chromenes

The Immobilized Zirconocene Chloride on Magnetite-Reduced Graphene Oxide: A Highly Efficient and Reusable Heterogeneous Nanocatalyst for One-Pot Three-Component Synthesis of Tetrahydrobenzo[B]Pyrans and Dihydropyrano[3,2-C]Chromenes

Reductions of Imines Using Zirconocene Chloride Hydride

Herein, we describe the fast, chemoselective, and clean reduction of imines with zirconocene chloride hydride. The reaction works well on aromatic and enolizable aliphatic aldimines, as well as ketimines. A range of N‐protecting groups and various functional groups were tolerated in the imine structure. The corresponding amines were obtained in high yields (65 % – quantitative) in short reaction times, and often, no purification was required other than standard aqueous workup and a short filtration.

Dehydropolymerisation of methylamine borane using a dinuclear 1,3-allenediyl bridged zirconocene complex

The dinuclear zirconocene chloride complex 1 is a highly active precatalyst for the dehydropolymerisation of methylamine borane. Comparison with mononuclear Zr chlorides and related dinuclear complexes suggests that the nature of the bridging motif is essential for the unique reactivity of 1.

Deposited zirconocene chloride on silica-layered CuFe2O4 as a highly efficient and reusable magnetically nanocatalyst for one-pot Suzuki-Miyaura coupling reaction

The novel core-shell magnetically nanoparticles of CuFe2O4@SiO2@ZrCp2Clx (x: 0–2) were synthesized and used as a highly efficient catalyst for Suzuki-Miyaura coupling reaction of various aryl halides with phenylboronic acid. The reactions were carried out in PEG-400 (70 °C) to afford biaryls in high to excellent yields. The core-shell nanocomposite was easily separated from the reaction by an external magnet and reused for 5 times without significant loss of its catalytic activity. Characterization of the zirconocene nanocomposite was carried out by FT-IR, SEM, EDX, XRD, ICP-OES, AGFM, TGA and BET analyses.

Reactions of (Diphenylphosphinomethyl)zirconocene Chloride with B(C6F5)3: Competition between P/B and P/Zr+ Frustrated Lewis Pair Reactions

The title complex Cp2ZrCl(CH2PPh2) reacts with B(C6F5)3 under specific conditions by phosphinomethyl transfer to give the phosphane-stabilized salt [Cp2ZrCl+][Ph2PCH2B(C6F5)3–]. X-ray crystal structure analysis showed the P–Zr coordination. This salt is trapped by phenyl isocyanate in an in situ three-component reaction to yield the respective P/Zr+ frustrated Lewis pair (FLP) addition product. In contrast, a mixture of Cp2ZrCl(CH2PPh2)/B(C6F5)3 and benzaldehyde under similar conditions gives the P/B FLP addition product. The Cp2ZrCl(CH2PPh2)/B(C6F5)3 system may form a P/B adduct [Cp2ZrCl(CH2PPh2)·B(C6F5)3] or a P/Zr+ adduct [Cp2ZrCl·PPh2CH2B(C6F5)3]. From the former it seems to show P/B FLP reaction and from the latter P/Zr+ FLP behavior; the outcome is dependent on the specific reagent and reaction conditions chosen.

μ-3,3′-Bis(trihydroboryl)[3]ferrocenophane]bis(chloridozirconocene)

The title compound, [FeZr2(C5H5)4Cl2(C13H18B2)], is a heteronuclear complex that consists of a [3]ferrocenophane moiety substituted at each cyclo­penta­dienyl (Cp) ring by a BH3 group; the BH3 group is bonded via two H atoms to the Zr atom of the zirconocene chloride moiety in a bidentate fashion. The two Cp rings of the [3]ferrocenophane moiety are aligned at a dihedral angle of 8.9 (4)° arising from the strain of the propane-1,3-diyl bridge linking the two Cp rings. [One methyl­ene group is disordered over two positions with a site-occupation factor of 0.552 (18) for the major occupied site.] The dihedral angles between the Cp rings at the two Zr atoms are 50.0 (3) and 51.7 (3)°. The bonding Zr⋯H distances are in the range 1.89 (7)–2.14 (7) Å. As the two Cp rings of the ferrocene unit are connected by an ansa bridge, the two Zr atoms approach each other at 6.485 (1) Å. The crystal packing features C—H⋯Cl inter­actions.

ChemInform Abstract: Zirconocene(iso-butyl) Chloride: In situ Generation of a Zirconocene( methyl) Chloride Equivalent for Use in Organic Synthesis.

Abstract Zirconocene( iso -butyl) chloride, 1 , which can be generated in situ from commercially available, inexpensive, and air-stable zirconocene dichloride, can function as a zirconocene(methyl) chloride equivalent.

ChemInform Abstract: Preparation of Alkyl Ethynyl Sulfides and Alkyl E-2-Iodoethenyl Sulfides.

Abstract An efficient method for the preparation of multi-gram quantities of ethynyl sulfides is exemplified by the synthesis of ethynyl n.pentyl sulfide. Treatment of the latter with zirconocene chloride hydride/N-iodosuccinimide gave E-2-iodoethenyl n.pentyl sulfide in high yield and stereoselectivity. The latter compound rearranged to the Z isomer on storage at −20°C.

Reactivity of [(2-Phosphino)ethenyl]zirconocene Chloride toward CpM(CO)3Cl (M = Mo, W): Formation of [(3-Phosphino)propenoyl]dicarbonyl(cyclopentadienyl)metal, {CpM(CO)2[(CO)CR═CRPPh2

Reaction of [(2-phosphino)ethenyl]zirconocene chloride (1) with CpM(CO)3Cl (M = Mo, W) in THF yielded the [(3-phosphino)propenoyl]dicarbonyl(cyclopentadienyl)metals {CpM(CO)2[(CO)CR═CRPPh2]} (2). W...

Characterization of β-B-Agostic Isomers in Zirconocene Amidoborane Complexes

The reaction of Cp(x)(2)ZrCl(2) (Cp(x) = Cp, Cp*) with ammonia borane in presence of n-butyllithium yielded Cp(2)Zr(Cl)NH(2)BH(3) and Cp(x)(2)Zr(H)NH(2)BH(3). These derivatives are isoelectronic with the ethyl zirconocene chloride and hydride, respectively, and feature a chelating amidoborane ligand coordinating through a Zr-N bond and a Zr-H-B bridge. In solution, each of the complexes consists of an equilibrium mixture of two isomers differing in the orientation of the amidoborane ligand with respect to the Zr-X bond (X = H, Cl), while in the solid state, only one isomer was observed. Such isomers have not been characterized for any metal complexes containing the isoelectronic beta-agostic ethyl ligand or any other agostic alkyl group.

Pentacarbonyl-2κ5C-chlorido-1κCl-bis[1(η5)-cyclopentadienyl](μ-1-oxidoethylene-1:2κ2O:C)chromium(0)zirconium(IV)

The title compound, [CrZr(C5H5)2(C2H3O)Cl(CO)5], consists of two metal centres, with a (penta­carbonyl­chromium)oxymethyl­carbene group coordinating as a monodentate ligand to the zirconocene chloride. π-Delocalization through the Zr—O—C=Cr unit is indicated by a short Zr—O distance [2.041 (3) Å] and a nearly linear Zr—O—C angle [170.5 (3)°]. Mol­ecules are aligned with their mol­ecular planes (through Zr, Cl, carbene and Cr) parallel to the ab plane. C—H⋯Cl inter­actions result in zigzag chains of mol­ecules propagating parallel to the b axis.

Preparation and Characterization of MCM-41 Supported Metallocene Catalysts for Olefin Polymerization

The effect of the structure and surface properties of support material on metallocene (zirconocene chloride) adsorption and catalyst activity in ethene polymerization was studied. Commercial Grace silica, mesoporous silicate, MCM-41, and aluminium-modified MCM-41 were used as supports. The highest amount of zirconocene dichloride was adsorbed on Al-modified MCM-41 (Si/Al=32), providing the most reactive sites for attachment of the active component on the support surface. The 13C-CPMAS NMR studies proved that Cp2ZrCl2 is bound to the support surface. Also the highest activity in ethene polymerization was obtained using this support.

Palladium-catalyzed reaction of 1-aza-5-germa-5-organobicyclo[3.3.3]undecane with aryl bromide

Successive treatment of triallylamine with zirconocene chloride hydride and germanium tetrachloride affords 1-aza-5-germa-5-chlorobicyclo[3.3.3]undecane, which is converted to the 5-organo derivatives by the reaction with Grignard or lithium reagents. The organo groups showed higher reactivities toward Stille-type coupling than the corresponding organotributylgermanes.

Formation and rearrangement of (siloxymethyl)zirconocene chloride complexes

Formation and rearrangement of (siloxymethyl)zirconocene chloride complexes

Synthesis of (.+-.)-N2-(benzenesulfonyl)-CPI, the protected A-unit of the antitumor antibiotic CC-1065, by two metal-initiated cyclizations

A new synthetic route to (±)-N 2 -(Benzensulfonyl)-CPI (16), the protected A-unit containing a cyclopropylhexadienone moiety of the highly potent antitumor antibiotic CC-1065 (1), from 5-(benzyloxy)-2-bromophenylamine (3) is described. The key steps are a zirconium- and a palladium initiated cyclization to give the two pyrrole moieties. Reaction of 4a with zirconocene (methyl) chloride leads after workup with I 2 to the 4-iodoindoline 7a, which was transformed into 12 and subsequently via Heck reaction into the pyrroloindoline 15

Synthesis of (±)-15-thia-15-deoxy-PGE1 methyl ester

The 15-thia-15-deoxy analogue of prostaglandin E1 methyl ester has been prepared by the zirconocene chloride mediated conjugate addition of an n-pentyl ethynyl sulfide derived anion to an appropriately substituted cyclopentenone. Similar methodology has also been used to prepare other 3-(3′-thia-1′-octenyl)-cyclopentanones.

Photoinduced molecular transformations. Part 150. A new total synthesis of (±)-α-Himachalene based on a Sequence involving [2+2] photoaddition and regioselective β-scission of alkoxyl radicals generated from the resulting cyclobutanols

A new total synthesis of α-himachalene, a sesquiterpene isolated from essential oil of a Himalayan cedar (Cedrus deodara Loud),has been achieved. It is based on a sequence involving the [2+2] photoaddition of a cyclic enone with a silyl enol ether, followed by a radical-induced ring expansion of the resulting fused cyclobutanol; the [2+2] photoaddition of cyclohexenone with 1-methyl-2-trimethylsiloxy-1-cyclopentene in benzene, followed by a treatment of the resulting photoadducts with acid gave a stereoisomeric mixture of 2-hydroxy-6-methyltricyclo[5.4.0.0 2,6]undecan-8-one(33%) accompanied by a product (27%) from a retroaldol reaction of an isomeric photoadduct. The former was transformed into 8- tert-butyldimethylsiloxy-6-methyltricyclo[5.4.0.0 2,6] undecan-2-ol via 3 steps. Irradiation of the hypoiodite generated from this protected fused cyclobutanol in benzene resulted in a β-scission of the ring fusion bond to give a mixture of functionalized bicyclo[5.4.0]undecanes, which was transformed into cis-6,6-dimethyl-8-hydroxybicyclo[5.4.0]undecane-2-ones via 3 steps. Its methylenation by a Wittig reaction, followed by oxidation of the resulting 2-methylenebicyclo [.5.4.0]undecan-8-ol, gave the corresponding bicycloundecan-8-one. Its ethoxycarbonylation, followed by reductive deoxygenation with zirconocene chloride hydride (Cp 2ZrHCl), gave ethyl 6,6-dimethyl-2-methylenebicyclo[5.4.0]undec-8-ene-9-carboxylate. The synthesis of (±)-α-himachalene was achieved by transforming the ethoxycarbonyl group into a methyl group by the standard method; the α,β-unsaturated ester was reduced into the corresponding alcohol with lithium alminium hydride. A reduction of the mesylate of the resulting alcohol with lithium triethylborohydride gave (±)-α-himachalene.