Paracyclophane Backbone Research Articles

Triphenylamine[3]arenes: Streamlining Synthesis of a Versatile Macrocyclic Platform for Supramolecular Architectures and Functionalities.

Triphenylamine[3]arenes (TPA[3]s), featuring [16]paracyclophane backbone with alternating carbon and nitrogen bridging atoms, were synthesized through a BF3 ⋅ Et2O-catalyzed cyclization reaction using triphenylamine derivatized monomers and paraformaldehyde. This molecular design yielded a series of TPA[3] macrocycles with high efficiency, with their facile derivatizations also successfully demonstrated. On account of the strong electron-donating properties of the TPA moieties, these TPA[3]s exhibit remarkable delayed fluorescence, and possess a significant affinity for iodine. Furthermore, their inherent three-fold symmetry rendered TPA[3]s as novel building blocks for the construction of extended frameworks and molecular cages. This advancement expands the versatility of discrete macrocycles into complex architectures, enhancing their applicability across a broad spectrum of applications.

Triphenylamine[3]arenes: Streamlining Synthesis of a Versatile Macrocyclic Platform for Supramolecular Architectures and Functionalities

AbstractTriphenylamine[3]arenes (TPA[3]s), featuring [16]paracyclophane backbone with alternating carbon and nitrogen bridging atoms, were synthesized through a BF3 ⋅ Et2O‐catalyzed cyclization reaction using triphenylamine derivatized monomers and paraformaldehyde. This molecular design yielded a series of TPA[3] macrocycles with high efficiency, with their facile derivatizations also successfully demonstrated. On account of the strong electron‐donating properties of the TPA moieties, these TPA[3]s exhibit remarkable delayed fluorescence, and possess a significant affinity for iodine. Furthermore, their inherent three‐fold symmetry rendered TPA[3]s as novel building blocks for the construction of extended frameworks and molecular cages. This advancement expands the versatility of discrete macrocycles into complex architectures, enhancing their applicability across a broad spectrum of applications.

Charge-State-Dependent Fragmentation of [2.2]Based Metallosupramolecular Cyclic Helicates in the Gas Phase.

A detailed mass-spectrometric study provides insight into the gas-phase fragmentation pathways of a cyclic helicate selectively built from four iron(II) centers and six [2.2]cyclophane-based ligands through the subcomponent self-assembly approach. The charge state of the precursor ion, i. e., the number of triflate anions accompanying the metallo-supramolecular core, has a strong influence on the observed fragmentations. The triply charged ion shows loss of a neutral ligand whereas ions of higher charge fragment by up to three different charge-separating pathways to minimize the charge density of the ions. Additional subsequent fragmentations of highly charged fragment ions include redox processes as well as splitting of the unusual paracyclophane backbone.

Influencing the Self-Sorting Behavior of [2.2]Paracyclophane-Based Ligands by Introducing Isostructural Binding Motifs.

Two isostructural ligands with either nitrile (Lnit) or isonitrile (Liso) moieties directly connected to a [2.2]paracyclophane backbone with pseudo‐meta substitution pattern have been synthesized. The ligand itself (Lnit) or its precursors (Liso) were resolved by HPLC on a chiral stationary phase and the absolute configuration of the isolated enantiomers was assigned by XRD analysis and/or by comparison of quantum‐chemical simulated and experimental electronic circular dichroism (ECD) spectra. Surprisingly, the resulting metallosupramolecular aggregates formed in solution upon coordination of [(dppp)Pd(OTf)2] differ in their composition: whereas Lnit forms dinuclear complexes, Liso exclusively forms trinuclear ones. Furthermore, they also differ in their chiral self‐sorting behavior as (rac)‐Liso undergoes exclusive social self‐sorting leading to a heterochiral assembly, whereas (rac)‐Liso shows a twofold preference for the formation of homochiral complexes in a narcissistic self‐sorting manner as proven by ESI mass spectrometry and NMR spectroscopy. Interestingly, upon crystallization, these discrete aggregates undergo structural transformation to coordination polymers, as evidenced by single‐crystal X‐ray diffraction.

A highly stable, Au/Ru heterobimetallic photoredox catalyst with a [2.2]paracyclophane backbone.

We report the synthesis and catalytic application of a highly stable distance-defined Au/Ru heterobimetallic complex. [2.2]Paracyclophane serves as a backbone, holding the two metal centers in a spatial orientation and metal-metal fixed distance. The Au/Ru heterobimetallic complex is highly stable, easily accessible and exhibits promising catalytic activity in a visible-light mediated dual Au/Ru Meyer-Schuster rearrangement.

Planar Chiral [2.2]Paracyclophane-Based Bisoxazoline Ligands: Design, Synthesis, and Use in Cu-Catalyzed Inter- and Intramolecular Asymmetric O–H Insertion Reactions

Centrally chiral bisoxazolines connected directly to a planar chiral [2.2]paracyclophane backbone were synthesized and evaluated as asymmetric ligands in Cu-catalyzed intermolecular ethanolic O-H insertion reactions of α-diazo esters. The reactivities and enantioselectivities of Cu complexes of the synthesized bisoxazoline ligands were lower than those of ligands without central chirality. However, planar chiral [2.2]paracyclophane-based bisoxazoline ligands with an inserted benzene spacer that had a sterically demanding isopropyl substituent showed good enantioselectivities in inter- and intramolecular aromatic O-H insertion reactions, without the aid of central chirality.

Planar‐Chiral [2.2]Paracyclophane‐Based Amides as Proligands for Titanium‐ and Zirconium‐Catalyzed Hydroamination

A synthetic route to racemic and enantiopure planar chiral [2.2]paracyclophanes with amide groups was developed to combine the well‐established reactivity of amides as N,O‐chelating ligands in hydroamination reactions with the planar chirality of the [2.2]paracyclophane backbone. A mono‐ as well as a tethered bis(amide) were synthesized and investigated as ligands for titanium and zirconium. Hydroamination reactivity studies showed their ability to translate their planar chirality into central chirality in the product.

Planar chiral [2.2]paracyclophane-based bis(thiourea) catalyst: application to asymmetric Henry reaction

A bis(thiourea) organocatalyst with a planar chiral [2.2]paracyclophane backbone has been synthesized and applied to the Henry reaction. The obtained high reactivity and enantioselectivity from the reaction of aromatic aldehydes with nitroalkanes suggested the significant potential of [2.2]paracyclophane to serve as the backbone of the organocatalyst.

Planar chiral [2.2]paracyclophane-based phosphine-Brønsted acid catalysts bearing exceptionally high reactivity for aza-Morita–Baylis–Hillman reaction

Several new planar chiral bifunctional phosphine compounds based on the [2.2]paracyclophane backbone with a pseudo-ortho substitution pattern have been synthesized and applied to the aza-Morita–Baylis–Hillman reaction. An enantiopure phosphine-phenol catalyst bearing an aryl group as a spacer connected to a phosphino group exhibited an exceptionally high reactivity (rt, 2–40min) and good enantioselectivity (up to 85% ee).

2.2]パラシクロファン骨格を有する面不斉触媒の設計と合成

2.2]パラシクロファン骨格を有する面不斉触媒の設計と合成

Aryl[2.2]paracyclophane‐Based Chiral Regioisomeric Analogs of Salicyl Aldehyde: Novel Sources for Construction of Phenoxy‐Imine Ligands

AbstractThe efficient, high‐yield approaches to two novel regioisomeric salicyl aldehyde analogs, 4‐formyl‐13‐(2‐hydroxyphenyl)‐[2.2]paracyclophane and 4‐formyl‐12‐(2‐hydroxyphenyl)‐[2.2]paracyclophane (iso‐FHPhPC and pseudo‐FHPhPC, respectively), constructed on the basis of an aryl[2.2]paracyclophane backbone are described. The key stage of the backbone formation is the Suzuki cross‐coupling of paracyclophanyl halides with arylboronic acids. Efficient procedures for the resolution of the racemic hydroxy aldehydes into enantiomers via Schiff bases with enantiomers of α‐phenylethyl amine were elaborated, and the absolute configurations of enantiomers were established on the basis of X‐ray analysis of diastereomeric imines. Starting from these chiral hydroxy aldehydes the first representatives of bi‐, tri‐, and tetradentate phenoxy‐imine ligands belonging to an aryl[2.2]paracyclophane family were obtained. The induction power of the ligands was tested in the Et2Zn asymmetric addition to aldehydes.

Synthesis of Planar Chiral Carbazole Derivatives Bearing a [2.2]Paracyclophane Skeleton

AbstractThe synthesis of planar chiral carbazoles bearing a [2.2]paracyclophane backbone is described. Starting from readily available 4‐bromo[2.2]paracyclophane planar chiral carbazoles are obtained in a two‐step synthesis by Pd‐catalyzed CN cross‐coupling and subsequent oxidative cyclization.

A planar chiral [2.2]paracyclophane derived N-heterocyclic stannylene

The reaction of pseudo-ortho-4,12-N,N'-diphenyldiamino-[2.2]paracyclophane ((±)-3) with Sn[N(SiMe(3))(2)](2) results in the formation of the monomeric planar chiral N-heterocyclic stannylene (±)-4, featuring a unique [2.2]paracyclophane backbone, which has been characterized by an X-ray diffraction study.

ChemInform Abstract: Synthesis of New Planar Chiral [2.2]Paracyclophane Schiff Base Ligands and Their Application in the Asymmetric Henry Reaction.

AbstractA variety of ligands combining a planar chiral paracyclophane backbone with enantiopure amino alcohols (I) and (II) is prepared and applied in the copper‐catalyzed asymmetric Henry reaction of aldehydes (III) and (VI) with nitromethane.

Co-Metal-Free Enantioselective Conjugate Addition Reactions of Zinc Reagents

Asymmetric conjugate addition of diethylzinc to cinnamaldehyde in a co-metal-free fashion by using N,O-ligands with planar and central chirality is described. Different modulations of the ligand structure, including several combinations of the chiral units, indicate that a [2.2]paracyclophane backbone is essential for the activity and the enantioselectivity of the generated active catalyst. By using the optimized ligand, an isolated yield of 90 % was obtained with up to 99 % ee.

Design, classification, and strategies of synthesis of modular bidentate ligands based on aryl[2.2]paracyclophane backbone

The aryl[2.2]paracyclophane backbone, which is a "hybrid" of a configurationally rigid [2.2]paracyclophanyl unit and a biphenyl unit, is proposed as a new source for the chiral ligands. Classification of such ligands in accordance with mutual arrangement of the functional substituents and their nature is also introduced. Key strategic approaches to the synthesis of regioisomeric biphenols and hydroxyaldehydes, including Suzuki cross-coupling reaction, lithiation/electrophilic quench, and chiral resolution, are elaborated. Examples of their further modification and application of several O,O- and N,O-ligands as chiral inductors in asymmetric catalysis are described.

Planar Chiral Imidazolium Salts in the Asymmetric Rhodium-Catalyzed 1,2-Addition of Arylboronic Acids to Aldehydes

Planar chiral imidazolium salts 8 and 13 were used as precursors for N-heterocyclic carbene ligands, which were applied in rhodium-catalyzed additions of arylboronic acids to aromatic aldehydes. With pseudo-ortho-disubstituted [2.2]paracyclophane (S,R p)-8b bearing a phosphinoyl substituent at the paracyclophane backbone, 38% ee has been achieved in this rather unexplored reaction.

Electrophilic substitution of dibromoparacyclophane: a route to novel paracyclophane phosphine ligands.

[reaction: see text] The regioselective functionalization of 4,12-dibromoparacyclophane via electrophilic aromatic substitution is reported for the first time. The functionalization of the paracyclophane backbone allows the development of a new family of paracyclophane-based phosphines (named ParaPhos) that opens the possibility of improved catalyst development and tuning while retaining all the catalysis potential of the PhanePhos family of ligands.

A novel class of bidentate ligands with a conformationally flexible biphenyl unit built into a planar chiral [2.2]paracyclophane backbone

We report the synthesis of a novel class of planar chiral bidentate aryl[2.2]paracyclophane ligands. For the first time in the [2.2]paracyclophanyl series the Pd-catalyzed Suzuki cross-coupling was employed for the formation of the arylparacyclophanyl skeleton. From the two possible approaches: (a) cross-coupling of [2.2]paracyalophanylboronic acids with aryl halides; (b) cross-coupling of [2.2]paracyclophanyl halides with arylboronic acids, the latter was found to be more efficient. This approach was successfully used for the synthesis of a wide range of aryl[2.2]paracyclophanes with different types of substitution patterns ( ortho-, pseudo- ortho- or pseudo- gem-arrangement of the functionally-substituted aryl fragment with respect to the substituent in the paracyclophane ring).

ChemInform Abstract: Phosphonites Based on the Paracyclophane Backbone: New Ligands for Highly Selective Rhodium‐Catalyzed Asymmetric Hydrogenation.

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