McMurry Coupling Research Articles

Photoinduced E to Z isomerization of tetraphenylethylene derivatives within organometallic supramolecular assemblies

Isolation of E-1,2-bis(4-bromophenyl)-1,2-diphenyl-ethylene from the E/Z isomer mixture obtained by a McMurry coupling reaction and reaction of this isomer with imidazole followed by N-alkylation with nBuBr and anion exchange yielded the bisimidazolium tetraphenylethylene (TPE) derivative H2-E-1(PF6)2. The reaction of H2-E-1(PF6)2 with Ag2O yielded the di-nuclear metallarectangle [Ag2(E-1)2](PF6)2 where the two bis-NHC donors E-1 bridge two silver atoms. Irradiation of [Ag2(E-1)2](PF6)2 leads to E/Z isomerization of the di-NHC ligand and formation of Z-1 in the mononuclear complex [Ag(Z-1)]PF6. Demetallation of the di-NHC ligand with NH4Cl/NH4PF6 yielded bisimidazolium salt H2-Z-1(PF6)2. The unique isomerization of the E-TPE derivative into its Z-isomer via metal complex formation/irradiation/demetallation cannot be achieved by irradiation of the individual imidazolium salt. The emissive properties of the TPE complexes [Ag2(E-1)2](PF6)2 and [Ag(Z-1)]PF6 have been investigated.

Dithienylethene-containing cyclic and linear conjugated molecules: Synthesis, photochromism, and photoluminescence

Cyclic and linear conjugated small molecules comprising dithienylethene (DTE) and thiophene groups were synthesized via Suzuki and McMurry couplings. The cyclic molecule was polymerized via ring-opening metathesis polymerization (ROMP) using a second-generation Grubbs catalyst to produce a DTE- and thienylene vinylene-containing conjugated polymer. DTE-containing small molecules exhibited (quasi-) reversible photochromism through alternating UV and visible light irradiation. The small linear molecules showed faster photochromism than the cyclic molecule. In contrast, the linear dimer and polymer did not undergo photochromism; however, they showed efficient photoluminescence, with quantum yields of 0.26 and 0.18, respectively.

An Ortho-Tetraphenylene-Based "Geländer" Architecture Consisting Exclusively of 52 sp2 -Hybridized C Atoms.

A new type of “Geländer” molecule based on a ortho‐tetraphenylene core is presented. The central para‐quaterphenyl backbone is wrapped by a 4,4’‐di((Z)‐styryl)‐1,1’‐biphenyl banister, with its aryl rings covalently attached to all four phenyl rings of the backbone. The resulting helical chiral bicyclic architecture consists exclusively of sp2‐hybridized carbon atoms. The target structure was assembled by expanding the central ortho‐tetraphenylene subunit with the required additional phenyl rings followed by a twofold macrocyclization. The first macrocyclization attempts based on a twofold McMurry coupling were successful but low yielding; the second strategy, profiting from olefin metathesis, provided satisfying yields. Hydrogenation of the olefins resulted in a saturated derivative of similar topology, thereby allowing the interdependence between saturation and physico‐chemical properties to be studied. The target structures, including their solid‐state structures, were fully characterized. The helical chiral bicycle was synthesized as a racemate and separated into pure enantiomers by HPLC on a chiral stationary phase. Comparison of recorded and simulated chiroptical properties allowed the enantiomers to be assigned.

Synthesis and Properties of Partially Saturated Fluorenyl-Derived [n]Helicenes Featuring an Overcrowded Alkene.

The straightforward, multigram-scale synthesis of the partially saturated H6 -fluoreno[n]helicenes (n=5 or 7) featuring a central, overcrowded alkene is described. The key cyclization step was based on an intramolecular McMurry reaction from the corresponding 1,5-diketones. Chiral stationary phase HPLC analysis and isomer separation indicate that each helicenic compound is constituted of three diastereoisomers at room temperature, i. e. the configurationally stable (R,R,P)/(S,S,M) pair of enantiomers and an apparently achiral compound resulting from the rapid interconversion between the (R,S,P) and (S,R,M) enantiomers. The partially saturated H6 -fluoreno[n]helicenes are oxidatively aromatized to give an efficient access to the corresponding fluoreno[n]helicenes. The chiroptical properties (vibrational and electronic circular dichroism) of the chiral, enantiopure compounds have been measured and analyzed by quantum-chemical calculations, confirming their helicoidal nature.

AIE-active discotic LC containing tetraphenylethylene and α-cyanostilbene: Synthesis, self-assembly and photophysical properties

ABSTRACT A novel α-cyanostilbene-containing tetraphenylethylene-based discotic LC with 3,4,5-tridecyloxy benzene units at the terminal was synthesized by Ti-catalyzed McMurry coupling, Pd-catalyzed Suzuki coupling and Knoevenagel reactions as key steps. The liquid crystal and photophysical properties were well demonstrated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), X-ray scattering (XRD), molecular dynamics (MD) and optical experiments. The compound could self-assemble into Colhex/p6mm mesophase in a wide temperature range. It is interesting that two discotic molecules formed one columnar slice, which was attributed to the twisted conformation of propeller-like TPE and α-cyanostilbene. The photophysical properties of the TPE-based DLCs including solvatochromism and aggregation-induced emission (AIE) behaviors were systematically investigated demonstrating large Stokes shifts, high fluorescence quantum yields and strong fluorescence in both solution and aggregated states. This work indicated that the combination of different AIE-active units into one LC molecule could induce complex self-assembly structure and excellent fluorescence properties.

Deciphering Benzene–Heterocycle Stacking Interaction Impact on the Electronic Structures and Photophysical Properties of Tetraphenylethene-Cored Foldamers

Deciphering Benzene–Heterocycle Stacking Interaction Impact on the Electronic Structures and Photophysical Properties of Tetraphenylethene-Cored Foldamers

Replacing the Z-phenyl Ring in Tamoxifen® with a para-Connected NCN Pincer-Pt-Cl Grouping by Post-Modification †.

Post-modification of a series of NCN-pincer platinum(II) complexes [PtX(NCN-R-4)] (NCN = [C6H2(CH2NMe2)2-2,6]–, R = C(O)H, C(O)Me and C(O)Et), X = Cl– or Br–) at the para-position using the McMurry reaction was studied. The synthetic route towards two new [PtCl(NCN-R-4)] (R = C(O)Me and C(O)Et) complexes used above is likewise described. The utility and limitations of the McMurry reaction involving these pincer complexes was systematically evaluated. The predicted “homo-coupling” reaction of [PtBr(NCN-C(O)H-4)] led to the unexpected formation of 3,3′,5,5′-tetra[(dimethylamino)methyl]-4,4′-bis(platinum halide)-benzophenone (halide = Br or Cl), referred to hereafter as the bispincer-benzophenone complex 13. This material was further characterized using X-ray crystal structure determination. The applicability of the pincer complexes in the McMurry reaction is shown to open a route towards the synthesis of tamoxifen-type derivatives of which one phenyl ring of Tamoxifen® itself is replaced by an NCN arylplatinum pincer fragment. The newly synthesized derivatives can be used as potential candidates in anti-cancer drug screening protocols. Two NCN-arylpincer platinum tamoxifen type derivatives, 5 and 6, were successfully synthesized and of 5 the separation of the diastereomeric E-/Z-forms was achieved. Compound 6, which is the pivaloyl protected NCN pincer platinum hydroxy-Tamoxifen® derivative, was obtained as a mixture of E-/Z-isomers. The new derivatives were further analyzed and characterized with 1H-, 13C{1H}- and 195Pt{1H}-NMR, IR, exact mass MS and elemental analysis.

"Shadow" Synthesis, Structure, and Electronic Properties of [2.2](1,6)(1,8)Pyrenophane-1-monoene.

An unexpected side product of a McMurry reaction was found to be a new [2.2]pyrenophane consisting of two pyrene units with different substitution patterns as well as different types and degrees of distortion from planarity. The new pyrenophane exhibits both monomer and intramolecular excimer fluorescence. Natural bond orbital (NBO) analysis revealed that there is an intramolecular charge-transfer interaction from the more distorted pyrene system to the less distorted one. The origin of the new pyrenophane was traced back to an impurity that was present a full five steps prior to the McMurry reaction from which it was isolated. The pathway to the pyrenophane shadowed that of the main synthetic route.

Synthesis and Molecular Properties of Partially Fluorinated DNTTs**

Abstract1,2,3,4‐Tetrafluoro‐dinaphthothienothiophene (F4DNTT) and 1,2,3,4,8,9,10,11‐octafluoro‐dinaphthothienothiophene (F8DNTT) were synthesized via bisthiomethyl alkene intermediates which were accessible by McMurry coupling or Wittig olefination of partially fluorinated naphthalene precursors. DFT‐based electronic structure calculations, near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy, and UV/Vis measurements were used for HOMO/LUMO gap determination and to analyze the electronic structures of the partially fluorinated DNTTs. Reduced exciton binding was observed in thin films.

Synthesis of pH-responsive triazine skeleton nano-polymer composite containing AIE group for drug delivery

We exploited a unique porous structure of the nano-covalent triazine polymer (NCTP) containing aggregation-induced emission (AIE) group to achieve controlled release and drug tracking in tumor acidic microenvironment. NCTP was synthesized by the Friedel-Crafts alkylation and the McMurry coupling reaction. It not only had strong doxorubicin (DOX)-loading capacity due to its high specific surface area and large pore volume, but also showed the significant cumulative drug release as a result of the pH response of triazine polymers. NCTP was induced luminescence after mass accumulation near tumor cells. Besides, it had excellent biocompatibility and obvious antineoplastic toxicity. The results demonstrate that NCTP as a utility-type drug carrier provides a new route for designing the multi-functional drug delivery platform.

Surface-confined formation of conjugated porphyrin-based nanostructures on Ag(111).

Porphyrin-based oligomers were synthesized from the condensation of adsorbed 4-benzaldehyde-substituted porphyrins through the formation of CC linkages, following a McMurry-type coupling scheme. Scanning tunneling microscopy, non-contact atomic force microscopy, and X-ray photoelectron spectroscopy data evidence both the dissociation of aldehyde groups and the formation of CC linkages. Our approach provides a path for the on-surface synthesis of porphyrin-based oligomers coupled by CC bridges - as a means to create functional conjugated nanostructures.

Unusual titanium-induced McMurry coupling of 4-oxo-4H-chromene-2-carbaldehydes enroute to bis-chromones

Ti/Zn-mediated McMurry coupling of a series of 4-oxo-4H-chromene-2-carbaldehydes afforded unusual chemoselective CH2–CH2 tethered bis-chromones.

Dual-mode coupling copolymerization of aryl dialdehyde and alkynylaldehyde monomers via Concurrent McMurry olefination and alkyne [2+2+2] cycloaddition trimerization reactions mediated by a low-valent titanium reagent

The application of a low-valent titanium reagent recently developed in our group, Ti(O-i-Pr)4/Me3SiCl/Mg, to the McMurry coupling polymerization of aryl dialdehyde monomers and [2 + 2 + 2] cycloaddition polymerization of aromatic diyne monomers is described. Furthermore, on the basis of these reactions, a low-valent titanium-mediated dual-mode coupling copolymerization of aryl dialdehyde and alkynylaldehyde monomers via concurrent McMurry olefination and alkyne cyclotrimerization reactions is proposed.

Reduction of Ethynylenes to Vinylenes in a Macrocyclic π-Extended Thiophene Skeleton Under McMurry Coupling Conditions.

McMurry coupling is one of the most useful and convenient tools for the preparation of π-conjugated molecules. However, for the synthesis of strained macrocycles containing ethynylene linkages, reduction of ethynylene to vinylene linkage sometimes took place. Especially, for the synthesis of macrocyclic π-extended thiophene hexamers using McMurry coupling of dialdehyde 1 composed of three thienylene, two ethynylene, and two formyl groups, reduction of ethynylenes to vinylenes often takes place to produce unique products in a one-pot procedure, depending on very small steric and electronic effects such as reaction temperature, amounts of titanium reagent, and substituents of thiophene hexamers. The attractive structures and functional properties of reduced thiophene hexamers have been determined using X-ray analysis and OFET measurements.

Olefin Synthesis by Deoxygenative Coupling of Carbonyl Compounds: From Stoichiometric to Catalytic

This highlight review describes the deoxygenative coupling of carbonyl compounds, starting with a brief historical presentation of stoichiometric reactions (McMurry coupling), then highlighting the...

Tetrabutyldideazaporphyrin

McMurry coupling of a dibutylpyrrole diacrylaldehyde afforded an unstable tetrabutyldideazaporphyrin. Although this porphyrin analogue was highly unstable, proton NMR spectroscopy demonstrated that it retained a high degree of diatropic character.

Triphenylethylene analogues: Design, synthesis and evaluation of antitumor activity and topoisomerase inhibitors

To structurally relate anticancer drug tamoxifen used in the treatment of breast cancer, a sequence of compounds is designed and synthesized as potential drug candidates. McMurry coupling reaction is used as the key synthetic step in the preparation of these analogues and the ratios of E/Z-isomers are determined on the basis of NMR and HPLC experiments. The new compounds are found to be cytotoxic in the micromolar range with 60 human tumor cell lines at one dose and five dose concentration levels. Detailed studies on the most active compounds 11-13 show these compounds are capable to inhibit the growth of cancer cells. Finally, with the aim to correlate the antiproliferative activity with an intracellular target(s), the effect on relaxation activity of DNA topoisomerase-II is assayed. The relevance of interaction of most active compounds with topoisomerase-II is demonstrated which is also supported by docking studies.

Enantioselective Synthesis of Planar Chiral Ferrocifens that Show Chiral Discrimination in Antiproliferative Activity on Breast Cancer Cells.

The design and first enantioselective synthesis of a series of chiral ferrocifens and ferrociphenols was realised by enantioselective palladium-catalysed intramolecular direct C-H bond activation followed by McMurry coupling. Biological evaluation revealed moderate anticancer activities on breast cancer cells and evidence of chiral discrimination between enantiomers. Treatment of the novel ferrocifens with Ag2 O revealed that these systems are unable to form a neutral quinone methide, yet still demonstrate marked antiproliferative properties against both the hormone-dependent MCF-7 and hormone-independent MDA-MB-231 cell lines. This bioactivity arises from two mechanisms: Fenton-type chemistry and the anti-estrogenic activity associated with the tamoxifen-like structure.

The electrosynthesis of highly photofunctional porous polymer PTCPE and the effect of BFEE on its electrochemical polymerization and fluorescence property

The development of porous polymer films with high emission efficiency simultaneously overcomes the unprocessable and poor photofunctionality limitations faced in the conjugated porous polymers (CPPs) field, and therefore has attracted more and more attentions. In this work, monomer 1,1,2,2-tetrakis(4-(9H-carbazol-9-yl)phenyl)ethene that contained AIE-active tetraphenylethylene and carbazole units had been synthesized via McMurry reaction. And its corresponding CPP (PTCPE) films were easily obtained using the electropolymerization method in CH2Cl2-BFEE mixtures without adding any supporting electrolyte. These CPPs films exhibited high fluorescence in the solid state because of AIE-active TPE. Their electrochemical polymerization and fluorescence properties could be changed by adjusting the polymerization conditions.

Total Synthesis of (±)-11-O-Debenzoyltashironin via Palladium-Catalyzed 5-endo Ene-yne Cyclization Enabled trans-5-6 Ring Fusion.

Illicium sesquiterpenes are a synthetically fascinating family of polycyclic natural products owing to their diversified pharmacological activities and structural complexity. Our cumulative efforts on developing a universal reductive coupling strategy toward stereoselective assembly of illicium sesquiterpenes recently resulted in a total synthesis of 11-O-debenzoyltashironin, a rare illicium sesquiterpene with a unique allo-cedrane carbon skeleton exhibiting prominent neurotropic activity, with complete stereochemical control. Our key tactics involved an unprecedented Pd(II)-catalyzed 5-endo ene-yne cyclization that directly allowed strained trans-5-6 ring fusion and a late-stage transannular McMurry coupling that furnished the compacted tetracyclic carbon skeleton rapidly.