Organozinc Research Articles

Preparation of Polyfunctional Organozinc Halides by an InX3 - and LiCl-Catalyzed Zinc Insertion to Aryl and Heteroaryl Iodides and Bromides.

A catalytic system consisting of InCl3 (3 mol %) and LiCl (30 mol %) allows a convenient preparation of polyfunctional arylzinc halides via the insertion of zinc powder to various aryl iodides in THF at 50 °C in up to 95 % yield. The use of a THF/DMPU (1:1) mixture shortens the reaction rates and allows the preparation of keto-substituted arylzinc reagents. In the presence of In(acac)3 (3 mol %) and LiCl (150 mol %), the zinc insertion to various aryl and heteroaryl bromides proceeds smoothly (50 °C, 2-18 h). Alkyl bromides are also converted to the corresponding zinc reagents in the presence of In(acac)3 (10 mol %) and LiCl (150 mol %) in 70-80 % yield.

Alkynylthioimidazolium Salts: Efficient Reagents for the Synthesis of Alkynyl Sulfides by Electrophilic Thioalkynylation.

The efficient synthesis of a series of alkynylthioimidazolium salts through reaction of organozinc compounds with dibromo(imidazolium)sulfuranes is reported. Addition of Grignard reagents to these new species provided a highly modular, clean, and scalable access to a broad variety of alkynyl sulfides in good-to-excellent yields. The utility of this protocol was showcased by the preparation of alkynyl sulfides, which are particularly difficult to obtain or simply unavailable through the existing methodologies. In addition, the synthetic method was extended to the preparation of alkynyl selenides.

Correction to “Asymmetric Copper-Catalyzed Carbozincation of Cyclopropenes en Route to the Formation of Diastereo- and Enantiomerically Enriched Polysubstituted Cyclopropanes”

The enantioselective synthesis of cyclopropylzinc reagents has been achieved via a copper-catalyzed carbozincation of 3,3-disubstituted cyclopropenes with diorganozinc reagents. The obtained organozinc compounds can be easily functionalized with a broad range of electrophiles, including palladium-catalyzed cross-couplings, affording highly substituted cyclopropanes. The operationally simple procedure using very low quantities of a commercially available and inexpensive copper catalyst provides a new tool for the synthesis of highly enantioenriched cyclopropanes as single diastereoisomers.

Progress of Chiral Schiff Bases with C1 Symmetry in Metal-Catalyzed Asymmetric Reactions.

In this Personal Account, various chiral Schiff base-metal-catalyzed enantioselective organic reactions are reported; the Schiff bases used were O,N,O- as well as N,N,P-tridentate ligands and N,N-bidentate ligands having C1 symmetry. In particular, the enantioselective addition of trimethylsilyl cyanide, dialkylzinc, and organozinc halides to aldehydes, enantioselective 1,4-addition of dialkylzinc to cyclic and acyclic enones, and asymmetric allylic oxidation are reported. Typically, ketimine-type Schiff base-metal complexes exhibited higher reactivity and enantioselectivity compared with the corresponding aldimine-type Schiff base-metal complexes. Notably, remarkable ligand acceleration was observed for all reactions. The obtained products can be used as key intermediates for optically active natural products and pharmaceuticals.

Influence of the halogen and organometallic function in a KCTP (Co)polymerization

ABSTRACTThe effect of changing the halogen and the organometallic function in a Kumada Catalyst Transfer Polycondensation (KCTP) of poly(3‐alkylthiophene)s (P3AT) is investigated. On the one hand, the bromine substituent is replaced with chlorine in the commonly used 2‐bromo‐5‐chloromagnesio‐3‐hexylthiophene. The effect on the homopolymerization is clear, since the stickiness decreases remarkably, but copolymerizations are hardly affected when a chlorinated monomer is used. Second, the option of changing the organometallic function is considered. Because also organozinc compounds provide a controlled P3AT polymerization with Ni(dppp)Cl2, but are less reactive than organomagnesium compounds, the effect of using zinc in one monomer during a copolymerization is investigated. However, it is found that the organometallic functions exchange during mixing of the monomers. Consequently, no effect is observed during copolymerizations. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3701–3706

Synthesis of two Zn(II) compounds from terpyridine-based ligand: Structures, crystal-to-crystal transformation and detection of nerve agent mimics

Reactions of ZnCl2 with 4′-(2,4-disulfophenyl)-2,2′:6′2″-terpyridine (H2DSPT) result to two new compounds with formula, {[Zn(DSPT)(H2O)2]·2H2O}n (1) and {[Zn(DSPT)(H2O)2]·H2O}n (2), respectively. Compound 1 is a binuclear complex, whereas compound 2 is a mononuclear organozinc compound. The coordination compounds can be controllable synthesized by adjust the pH value. The thermal behavior of 1 was explored by TG and VT-PXRD, which indicated that it undergo crystal-to-crystal transformation manner. Both compounds 1 and 2 show weak luminescence in both solid state and water emulsions compared with H2DSPT. The luminescence intensity of compound 1 can strongly enhanced by the addition of diethylchlorophosphonate (DCP), but significant less influenced by dimethylmethylphosphonate (DMMP), diethylcyanophosphonate (DCNP) and other selected organophosphate, which make compound 1 has potential application on nerve-agent detection.

ChemInform Abstract: Advances in the Chemistry of Organozinc Reagents

AbstractReview: [43 refs.

Synthesis of Trimeric Organozinc Compounds and their Subsequent Reaction with Oxygen.

A conventional solution‐based route to a cyclic trimeric organozinc compound [{Zn(Et)(β‐diketonate)}3] (β‐diketonate=OC(OMe)CHC(Me)O, 1) is described, with 1 structurally characterized for the first time. The ligand selection of bidentate β‐diketonates is shown to be key to isolating a cyclic trimer. Additional reaction of β‐diketonates with diethyl zinc were spectroscopically characterized as compounds of the type [{Zn(Et)(β‐diketonate)}n] (β‐diketonate=OC(Me)CHC(Me)O, 2, OC(OtBu)CHC(Me)O, 3). Further studies have shown that selective oxidation of these species produces cubanes of the general formula [{Zn(OC(R)CHC(Me)O)2Zn(Et)OEt}2] (R=OMe, 4; Me, 5; OtBu, 6), allowing a high oxygen content whilst remaining structurally suitable for use as precursors. The successful deposition of thin films of zinc oxide through aerosol‐assisted chemical vapor deposition (AACVD), using a novel precursor, is described and fully characterized.

Rotational spectroscopy of ClZnCH3 (X1A1): Gas-phase synthesis and characterization of a monomeric Grignard-type reagent

The pure rotational spectrum of the organozinc halide, ClZnCH3 (X1A1), has been measured using Fourier-transform microwave (FTMW) and millimeter-wave direct-absorption methods in the frequency range 10–296GHz. This work is the first study of ClZnCH3 by gas-phase spectroscopy. The molecule was created in a DC discharge from the reaction of zinc vapor, produced either by a Broida-type oven or by laser ablation, with chloromethane in what appears to be a metal insertion process. Rotational and chlorine quadrupole constants were determined for three zinc isotopologues. The ZnCl bond was found to be partly ionic and significantly shorter than in EtZnCl.

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties.

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

Study of the reaction of 3,6-di-tert-butyl-о-benzoquinone with organozinc and organocadmium compounds

The effect of substituents in the reactions of 3,6-di-tert-butyl-о-benzoquinone with organozinc and organocadmium compounds, leading to three types of products: 3-alkyl-6-tert-butyl-о-benzoquinones, 4-alkyl-3,6-di-tert-butyl-о-benzoquinones, and 2-alkoxy-(or 2-phenoxy)-3,6-di-tert-butylphenols. Correlation analysis gave evidence to show that the first- and second-type products are formed by nucleophilic 1,2- and 1,4-addition, while substituted phenols result from single-electron transfer.

ChemInform Abstract: Coupling of α,α‐Difluoro‐Substituted Organozinc Reagents with 1‐Bromoalkynes.

α,α-Difluoro-substituted organozinc reagents generated from conventional organozinc compounds and difluorocarbene couple with 1-bromoalkynes affording gem-difluorinated alkynes. The cross-coupling proceeds in the presence of catalytic amounts of copper iodide in dimethylformamide under ligand-free conditions.

Asymmetric Copper-Catalyzed Carbozincation of Cyclopropenes en Route to the Formation of Diastereo- and Enantiomerically Enriched Polysubstituted Cyclopropanes

The enantioselective synthesis of cyclopropylzinc reagents has been achieved via a copper-catalyzed carbozincation of 3,3-disubstituted cyclopropenes with diorganozinc reagents. The obtained organozinc compounds can be easily functionalized with a broad range of electrophiles, including palladium-catalyzed cross-couplings, affording highly substituted cyclopropanes. The operationally simple procedure using very low quantities of a commercially available and inexpensive copper catalyst provides a new tool for the synthesis of highly enantioenriched cyclopropanes as single diastereoisomers.

Coupling of α,α-difluoro-substituted organozinc reagents with 1-bromoalkynes

α,α-Difluoro-substituted organozinc reagents generated from conventional organozinc compounds and difluorocarbene couple with 1-bromoalkynes affording gem-difluorinated alkynes. The cross-coupling proceeds in the presence of catalytic amounts of copper iodide in dimethylformamide under ligand-free conditions.

ChemInform Abstract: Reaction of gem‐Difluorinated Organozinc Reagents with β‐Nitrostyrenes.

AbstractA novel reactivity pattern of gem‐difluorinated organozinc compounds in the copper(I)‐catalyzed reaction with β‐nitrostyrenes is described.

One-Step Synthesis of Racemic 6-Methyloctan-3-One, an Alarm Pheromone Component of Ants of the Genus Crematogaster

6-Methyloctan-3-one (1) was identified as a component of the alarm pheromone of ants of the genus Crematogaster [1]. Several syntheses of this compound as the racemate and an enantiomer are known [2–6]. However, many of them involve several steps and most are labor-intensive and require costly starting materials. We developed a convenient and effective synthetic pathway for a racemic analog of 1 that was based on our recently proposed regioselective carbonylation of 1-alkenes using Et2Zn and TaCl5 catalyst [7]. The reaction of but-1-ene with Et2Zn in the presence of TaCl5 (Et2Zn–but-1-ene–TaCl5 = 110:100:5; Et2Zn concentration 1.0 mmol/mL in hexane, 20°C, 5 h) formed organozinc compound 2. For this, hexane (20 mL) was cooled to –15°C and treated with but-1-ene (2.25 ml, 20 mmol) cooled to –30°C. Then, the solution was cooled to –15–20°C, treated with Et2Zn (2.25 mL, 22 mmol) and TaCl5 (0.4 g, 1 mmol), heated gradually to room temperature, stirred for 5 h, cooled to –5°C, and treated dropwise with propionylchloride (3, 1.74 mL, 20 mmol) in hexane. All these operations were performed under a dry Ar atmosphere. The resulting reaction mixture was stirred for 2 h and treated with aqueous HCl solution (10%). The resulting 1 was extracted by Et2O (3 50 mL). The extracts were dried over anhydrous MgSO4. The solvent was distilled off. The residue was chromatographed (SiO2, hexane) to afford 1 (2.69 g, 99% pure) in 95% yield based on 3 (Scheme 1). The structure of 1 was proven using IR, PMR, and 13C NMR spectral methods and GC-MS in addition to comparison with an authentic sample [6].

ChemInform Abstract: Continuous Synthesis of Organozinc Halides Coupled to Negishi Reactions.

The Negishi cross-coupling is a powerful CC bond forming reaction. The method is less commonly used relative to other cross-coupling methods in part due to lack of availability of organozinc species. While organozinc species can be prepared, problems with reproducibility and handling of these sensitive species can complicate these reactions. Herein, we describe the continuous formation, using an activated packed-bed of metallic zinc, and subsequent use of organozinc halides. We demonstrate that a single column of zinc can provide excellent yields of organozinc halides and that they can be used downstream in subsequent Negishi cross-couplings. The preparation of the zinc column and the scope of the reaction are discussed.

ChemInform Abstract: Chiral Ligands Derived from Monoterpenes: Application in the Synthesis of Optically Pure Secondary Alcohols via Asymmetric Catalysis

AbstractReview: [55 refs.

Synthesis of Organozinc Halides and Subsequent Negishi Coupling in Flow

Key words continuous flow reaction - Negishi coupling - zinc insertion - palladium

Nanoribbon‐Structured Organo Zinc Phosphite Polymorphs with White‐Light Photoluminescence

AbstractThe first neutral organo zinc phosphites composed of 2.8 nm‐wide ribbons were obtained in pure phases and exhibit near‐white‐light photoluminescence (PL). By using the “mesitylene strategy”, interesting polymorphism in the system of NTHU‐14 was discovered. The S‐shaped ribbons are arranged into R and L arrays, resulting in RLR and RRR stacking for two polymorphs. π–π interactions exist within each array and hydrogen bonding between adjacent arrays. Besides a common ligand‐based emission band at 410 nm, the PL curves of polymorphs 14‐α and 14‐β are distinctly different: 14‐α gave a defect‐based emission at 565 nm, whereas 14‐β primarily shows a π‐excimer‐based emission at 535 nm. Electron paramagnetic resonance (EPR) data disclosed that radical species exist in the reaction and that the two phases were growing from different environments. Based on these results, the origin of the 565 nm band can be ascribed to lattice defects, and one possible cause of 14‐β not showing noticeable yellow emission is identified.