Triple Helical Ir(ppy)3 Phenylene Cage Prepared by Diol-Mediated Benzannulation: Synthesis,Resolution, Absolute Stereochemistry and Photophysical Properties

Cyclometalation of a triple helical N-doped phenylene cage prepared by ruthenium(0)-catalyzed diol–diene benzannulation delivers a chiral, conformationally constrained Ir(ppy)₃ analogue. Like the parent complex, fac-Ir(ppy)₃, the iridium-containing PAH-cage is phosphorescent, but displays enhanced resistance to oxygen quenching.     

Synthesis and Photophysical Properties of Soluble N-Doped Rubicenes via Ruthenium-Catalyzed Transfer Hydrogenative Benzannulation

Ruthenium-catalyzed butadiene-mediated benzannulation enabled the first synthesis of 3,10-(di-tert-butyl)rubicene and its N-doped derivatives as well as preliminary studies on their photophysical properties. Unlike the parent rubicene and 3,10-(di-tert-butyl)rubicene, which adopt classical herringbone-type packing motifs in the solid state, the N-doped congener 7 b displayed columnar packing with an alternating co-facial arrangement of aromatic and heteroaromatic substructures.     

Benzannulation through Ruthenium(0)-Catalyzed Transfer Hydrogenative Cycloaddition: Precision Synthesis and Photophysical Characterization of Soluble Diindenoperylenes

The first application of ruthenium(0)-catalyzed 1,2-dione-diyne [2+2+2] cycloaddition to PAH construction is achieved by the precision synthesis of soluble diindenoperylenes (DIPs), the electronic structures of which were investigated using steady-state absorption and emission, transient absorption, cyclic voltammetry and time-dependent density functional theory     

Non‐linear,cata‐Condensed,Polycyclic Aromatic Hydrocarbon Materials: A Generic Approach and Physical Properties

A generic approach to the regiospecific synthesis of halogenated polycyclic aromatics is made possible by the one‐ or two‐directional benzannulation reactions of readily available (ortho‐allylaryl)trichloroacetates (the “BHQ” reaction). Palladium‐catalysed cross‐coupling reactions of the so‐formed haloaromatics enable the synthesis of functionalised polycyclic aromatic hydrocarbons (PAHs) with surgical precision. Overall, this new methodology enables the facile mining of chemical space in search of new electronic functional materials.     

Rhodium‐Catalyzed Oxidative Benzannulation of N‐Pivaloylanilines with Internal Alkynes through Dual C−H Bond Activation: Synthesis of Highly Substituted Naphthalenes

An efficient method was developed for the synthesis of highly substituted naphthalenes through rhodium‐catalyzed oxidative benzannulation of N‐pivaloylanilines with internal alkynes. The benzannulation reaction proceeded smoothly through dual C?H bond activation to produce the corresponding highly substituted naphthalene products in satisfactory to good yields.     

Synthesis,Structures, and Physical Properties of Benzo[k]fluoranthene‐Based Linear Acenes

This work describes the syntheses, crystal structures, photophysical properties, and electro‐chemical analyses of benzo[k]fluoranthene‐based linear acenes, together with ab initio density functional theory computations on them. The molecules were prepared in generally moderate to good yields through Pd‐catalyzed cycloadditions between 1,8‐diethynylnaphthalene derivatives and aryl iodides. This protocol is simpler and more efficient than conventional methods. The scope and limitations of this reaction were examined. The structures of compounds 4 hb , 15 ac , 17 ab , 19 ac , and 24 je were determined by X‐ray analysis; they are either bent or twisted, rather than planar. The photophysical and electrochemical properties of these cycloadducts were also investigated and compared with computational predictions based on density functional theory.     

On a possible growth mechanism for polycyclic aromatic hydrocarbon di-cations: C(7)H(6)(2+) + C(2)H(2)

The mechanism of the bond-forming reaction between C(7)H(6) (2+) and C(2)H(2) to yield C(9) entities has been investigated by density functional theory calculations with close comparison with experimental data. It is shown that the reaction produces the C(9)H(6) (2+) and C(9)H(7) (2+) di-cations with geometries most probably derived from the indene skeleton. In comparison, the formation of linear structures of di-cations is much more energy-demanding and therefore appears improbable.     

Regioselective Dihalohydration Reactions of Propargylic Alcohols: Gold‐Catalyzed and Noncatalyzed Reactions

The regioselective conversion of propargylic alcohols into previously unreported α,α‐diiodo‐β‐hydroxyketones was achieved by treatment with N‐iodosuccinimide in the presence of a gold catalyst. The corresponding α,α‐dichloro‐β‐hydroxyketones were obtained by treatment with trichloroisocyanuric acid in the absence of a catalyst. The latter reaction can be extended to other alkynols. These transformations can be used to prepare potentially useful halogenated building blocks. Preliminary mechanistic studies suggest that the reaction involves participation of the acetonitrile solvent in the formation of a 5‐halo‐1,3‐oxazine intermediate.     

Helical Nanographenes Containing an Azulene Unit: Synthesis,Crystal Structures,and Properties

Three unprecedented helical nanographenes ( 1 , 2 , and 3 ) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X‐ray crystallographic analysis. The embedded azulene unit in 2 possesses a record‐high twisting degree (16.1°) as a result of the contiguous steric repulsion at the helical inner rim. Structural analysis in combination with theoretical calculations reveals that these helical nanographenes manifest a global aromatic structure, while the inner azulene unit exhibits weak antiaromatic character. Furthermore, UV/Vis‐spectral measurements reveal that superhelicenes 2 and 3 possess narrow energy gaps ( 2 : 1.88 eV; 3 : 2.03 eV), as corroborated by cyclic voltammetry and supported by density functional theory (DFT) calculations. The stable oxidized and reduced states of 2 and 3 are characterized by in‐situ EPR/Vis–NIR spectroelectrochemistry. Our study provides a novel synthetic strategy for helical nanographenes containing azulene units as well as their associated structures and physical properties.     

Synthesis and Structures of Polyphenylphenanthrenes

1,2,3,4,5,6,7,8-Octaphenylphenanthrene ( 4 ) and decaphenylphenanthrene ( 5 ) were prepared by very short syntheses (two or three steps) from tetraphenylfuran and polybrominated benzene derivatives. The X-ray structures of compounds 4 and 5 show them to be quite crowded, with the phenanthrene cores twisted by about 40° due to the clash of the C4 and C5 phenyl groups. Compound 4 was resolved by chromatography on a chiral support, and its free energy of activation for racemization was determined to be 24.6 kcal mol⁻¹ at 40 °C. Computational studies indicate that compound 5 has a racemization barrier approximately 6 kcal mol⁻¹ lower than 4 , and thus 5 would not be configurationally stable at room temperature.     

The Precise Synthesis of Phenylene‐Extended Cyclic Hexa‐peri‐hexabenzocoronenes from Polyarylated [n]Cycloparaphenylenes by the Scholl Reaction

The longitudinal extension of cycloparaphenylenes (CPP) towards ultrashort carbon nanotubes (CNTs) is essential for the solution based bottom‐up synthesis of CNTs. Herein, the longitudinal extension of the CPP skeleton by the introduction of hexaphenylbenzene units towards polyarylated [n]CPPs is described. Further, the applicability of the Scholl reaction to selectively form graphenic sidewalls is demonstrated. The ring size and substitution patterns of the polyarylated [n]CPPs were varied to overcome strain‐induced side reactions during the oxidative cyclodehydrogenation and cyclic para‐hexa‐peri‐hexabenzocoronene trimers ([3]CHBCs) were selectively obtained. This concept is envisioned as an access to ultrashort carbon nanotubes subject to the condition that further benzene rings with the right connectivity will be inserted.     

Helical Ullazine-Quinoxaline-Based Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic azomethine ylides (PAMYs) are powerful building blocks in the bottom-up synthesis of internally nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) through 1,3-cycloaddition reactions. In this work, the cycloaddition reaction of PAMYs to asymmetric ortho-quinones is presented, which, in contrast to the addition to symmetric para-quinones, facilitates subsequent condensation reactions and allows the synthesis of three helical N-PAHs with ullazine-quinoxaline ( UQ - 1 – 3 ) backbones. UQ - 1 and UQ - 2 possess two helical centers; however, single-crystal X-ray analysis together with the computational modeling of UQ - 3 elucidate the formation of only the thermodynamically most stable geometry with four helical centers in a (P,P,M,M) configuration. For the series UQ - 1 – 3 , the number of redox steps is directly correlated with the number of ullazine or quinoxaline units incorporated into the targeted molecular backbones. A detailed investigation of the spectroscopic and magnetic properties of the radical cation and anion as well as the dication and dianion species by in situ EPR/UV/Vis-NIR spectroelectrochemistry is provided. The excellent optical and redox properties combined with helical geometries render them possibly applicable as chiral emitter or ambipolar charge transport material in organic electronics.     

Environmentally benign chlorination and bromination of aromatic amines, hydrocarbons and naphthols

A simple and efficient procedure for chlorination and bromination of aromatic amines, hydrocarbons and naphthols by the action of aqueous hydrohalic acid and hydrogen peroxide is described. This environmentally clean and safe procedure involves in situ generation of the active halogen and its uncatalyzed reaction with the substrates in this study.     

溴代稠环芳烃的氧化溴化法合成

以HBr/H2O2为溴化体系,采用氧化溴化法合成了6种稠环芳烃的溴化物。 合成反应无需催化剂,通过控制反应温度和溴化试剂用量,可以在稠环芳烃化合物的活性位选择性地单溴化或双溴化,产率可达51.1%～94.2%。 产品经熔点和1H NMR法确认,合成操作简单安全,环境污染少,有工业应用前景。     

Kekulé-based Valence Bond Model. II. Diels-Alder Reactivity of Polycyclic Aromatic Hydrocarbons

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Palladium-Catalyzed Regioselective peri- and ortho-Halogenation of 1-Naphthaldehydes: Application to the Synthesis of Polycyclic Natural Product Skeletons

Herein, a regioselective bromination or chlorination reaction of 1-naphthaldehydes is described. Without additive, the palladium-catalyzed C−H halogenation showed a C8-regioselectivity, whereas the formation of an aromatic imine intermediate allowed a switch to a C2-reactivity. Mechanistic studies and DFT calculations were performed to explain the regioselectivity and the synthesized halogenated products were used as key building blocks to access polycyclic natural product skeletons.     

Exceptional molecular architectures via cycloadditions to pyrenequinones

The thermal reaction of phencyclone (2) with a 1:1 mixture of 1,8-pyrenequinone (4) and 1,6-pyrenequinone (5) yields 2:1 adducts only of compounds 2 and 4. The observed polycyclic aromatic hydrocarbon 8 is formed via double Diels-Alder addition of 2 to 4, and the polycyclic ketone 9 arises from a combination of Diels-Alder and hetero-Diels-Alder reactions of 2 and 4. In contrast, Lewis acid-catalyzed reactions of 2, 4, and 5 give 2:1 adducts only of 2 and 5. The chief product, polycyclic diketone 10, is derived from a double hetero-Diels-Alder addition of 2 to 5. X-ray analysis of compound 8 shows it to be an exceptionally large polycyclic aromatic arch, and the X-ray structure of 10 reveals it to be a chiral molecular tweezer.     

Uncatalyzed,Regioselective Oxidation of Saturated Hydrocarbons in an Ambient Corona Discharge

Atmospheric pressure chemical ionization (APCI) in air or in nitrogen with just traces of oxygen is shown to yield regioselective oxidation, dehydrogenation, and fragmentation of alkanes. Ozone is produced from ambient oxygen in situ and is responsible for the observed ion chemistry, which includes partial oxidation to ketones and C?C cleavage to give aldehydes. The mechanism of oxidation is explored and relationships between ionic species produced from individual alkanes are established. Unusually, dehydrogenation occurs by water loss. Competitive incorporation into the hydrocarbon chain of nitrogen versus oxygen as a mode of ionization is also demonstrated.     

Thermodynamically Stable o-Quinodimethane: Synthesis,Structure, and Reactivity

Thermal isomerization of cyclobutaphenanthrene to o-quinodimethane was investigated. Sterically congested substituents or electron-donating substituents on the four-membered ring promoted the ring-opening, affording o-quinodimethane in a relatively stable form. Isolation of the newly prepared o-quinodimethane allowed its structural elucidation and investigation of its potential reactivities. Dual [4+2] cycloaddition of an aryne and o-quinodimethane afforded tetrabenzopentacene, demonstrating the synthetic application of the isolated compound.