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An Fe(III)-promoted oxidative annulation reaction was developed for the synthesis of 1,2-naphthoquinones. A variety of substituted arylglyoxals and internal alkynes undergo the transformation in the presence of FeCl3 at room temperature to afford the 1,2-naphthoquinone products in good yields in a short reaction time. Interestingly, the products show unusual pseudomigration of the substituent on the arene ring of arylglyoxals. A possible mechanism involving Fe(III)-promoted formation of a vinyl cation from arylglyoxal and alkyne, electrophilic addition of the vinyl cation to the ipso carbon of the aryl group to give a spiral intermediate, and then migration of the keto carbon to the ortho carbon was proposed as key steps and verified using quantum mechanics.

Simultaneous enhancement of out-coupling efficiency, internal quantum efficiency, and color purity in thermally activated delayed fluorescence (TADF) emitters is highly desired for the practical application of these materials. We designed and synthesized two isomeric TADF emitters, 2DPyM-mDTC and 3DPyM-pDTC, based on di(pyridinyl)methanone (DPyM) cores as the new electron-accepting units and di(tert-butyl)carbazole (DTC) as the electron-donating units. 3DPyM-pDTC, which is structurally nearly planar with a very small ΔEST, shows higher color purity, horizontal ratio, and quantum yield than 2DPyM-mDTC, which has a more flexible structure. An electroluminescence device based on 3DPyM-pDTC as the dopant emitter can reach an extremely high external quantum efficiency of 31.9% with a pure blue emission. This work also demonstrates a way to design materials with a high portion of horizontal molecular orientation to realize a highly efficient pure-blue device based on TADF emitters.

Two benzoylpyridine-carbazole based fluorescence materials DCBPy and DTCBPy, bearing two carbazolyl and 4-(t-butyl)carbazolyl groups, respectively, at the meta and ortho carbons of the benzoyl ring, were synthesized. These molecules show very small ΔEST of 0.03 and 0.04 eV and transient PL characteristics indicating that they are thermally activated delayed fluorescence (TADF) materials. In addition, they show extremely different photoluminescent quantum yields in solution and in the solid state: in cyclohexane the value are 14 and 36%, but in the thin films, the value increase to 88.0 and 91.4%, respectively. The OLEDs using DCBPy and DTCBPy as dopants emit blue and green light with EQEs of 24.0 and 27.2%, respectively, and with low efficiency roll-off at practical brightness level. The crystal structure of DTCBPy reveals a substantial interaction between the ortho donor (carbazolyl) and acceptor (4-pyridylcarbonyl) unit. This interaction between donor and acceptor substituents likely play a key role to achieve very small ΔEST with high photoluminescence quantum yield.

We describe a highly step and atom economical cobalt-catalyzed cyclization of 1,6-enynes with aldehydes to synthesize functionalized pyrrolidines and dihydrofurans with high chemo- and stereoselectivity. The catalytic reaction plausibly proceeds via the cobaltacycle intermediate generated from the reaction of enyne substrate with cobalt catalyst, followed by switchable C-H functionalization of weakly coordinating aldehydes depending on the electronic nature of the ligand.

Pd-catalyzed selective ortho-olefination of arenes assisted by an allylic C-C double bond at room temperature using O(2) as a terminal oxidant is described. A possible mechanism involving the initial coordination of allylic C═C bond to Pd followed by selective o-C-H bond metalation is proposed.

Cobalt complex/Zn systems effectively catalyze the reductive coupling of activated alkenes with alkynes in the presence of water to give substituted alkenes with very high regio- and stereoselectivity in excellent yields. While the intermolecular reaction of acrylates, acrylonitriles, and vinyl sulfones with alkynes takes place in the presence of CoI2(PPh3)2/Zn, the reaction of enones and enals with alkynes requires the use of the CoI2(dppe)/Zn/ZnI2 system. The intramolecular reductive coupling of activated alkenes (enones, enals, acrylates, and acrylonitriles) with alkynes also works efficiently. Further a variety of cyclic lactones and lactams were prepared using this methodology. Possible mechanistic pathways are proposed based on a deuterium-labeling experiment carried out in the presence of D2O.

A new method for the synthesis of substituted 2-acylallylmetal reagents in a highly regio- and stereoselective fashion involving a three-component assembly of allenes, acyl chlorides, and bimetallic reagents (B-B, Si-Si, and Sn-Sn) catalyzed by phosphine-free palladium complexes is described. Treatment of various allenes (CR(2)R(3)=C=CH(2)) with acyl chlorides (R(1)COCl) and bispinacolatodiboron in the presence of PdCl(2)(CH(3)CN)(2) in toluene at 80 degrees C gave 2-acylallylboronates in moderate to good yields. The acylsilation of allenes with acid chlorides and hexamethyldisilane (5) proceeded successfully in the presence of Pd(dba)(2) in CH(3)CN affording the corresponding allylsilanes (CR(2)R(3)=C(COR(1))CH(2)SiMe(3)) in good to moderate yields. Several chloroformates (R(4)OCOCl) also react with 1,1-dimethylallene (2a) and 5 to afford allylsilanes (CR(2)R(3)=C(COOR(4))CH(2)SiMe(3)) in 66-70% yields. Acylstannation of allenes could also be achieved by slow addition of hexabutylditin (10) to the reaction mixture of acyl chloride (or chloroformate) and allene 2a in CH(3)CN in the presence of Pd(dba)(2) at 60 degrees C; the corresponding 2-substituted allylstannanes were isolated in moderate to good yields. The above catalytic reactions are completely regioselective and highly stereoselective. A mechanism is proposed to account for the catalytic reactions and the stereochemistry.

A CoI(2)/(R)-BINAP, Zn, ZnI(2), H(2)O system efficiently catalyzes the intermolecular asymmetric reductive coupling of alkynes with cyclic enones to afford highly regio- and enantioselective β-alkenyl cyclic ketones. A possible mechanism that involves the formation of a cobaltacyclopentene intermediate from the alkyne and cyclic enone is proposed.

A palladium-catalyzed chelation-assisted C-H activation of alkyl aryl ketones and their reaction with aryl iodides to afford ortho-arylated products is described. For sec-alkyl aryl ketones, the catalytic reaction proceeds further to give 10,10-dialkylphenanthrone derivatives. A possible reaction mechanism involving directed dual C-H bond activation and enolate cyclization for the formation of 10,10-dialkylphenanthrone derivatives is proposed.

A novel method for the construction of a fused cyclohexadiene ring on C60 based on a nickel-promoted [2+2+2] cycloaddition of 1,6-diynes is described. Treatment of C60 with terminal 1,6-diynes (HC⋮CCH2)2X) in the presence of NiCl2(PPh3)2, Zn, and PPh3 at 90 °C in toluene afforded [2+2+2] bicyclic hexadiene derivatives (X = C(CO2Me)2 (2a), C(CO2Et)2 (2b), C(COMe)2 (2c), CH2 (2d), O (2e), NSO2-p-C6H5CH3 (2f), C(SO2Ph)2 (2g), and (2h) in good yields. Spectral data for products 2a−h indicated that the cycloaddition of diynes to C60 occurs across a 6,6-ring junction on the fullerene. On the basis of the established chemistry of metal-mediated [2+2+2] cycloaddition, a mechanism is proposed to account for the present nickel-mediated reaction. All the hexadiene derivatives 2a−h in solution are readily oxidized by molecular oxygen in the presence of light at ambient temperature. The oxidation process of compound 2a in chloroform-d was monitored by 1H NMR spectroscopy, and the results showed that 2a first reacted w...

The electrochemistry and electrogenerated chemiluminescence (ECL) of three phenanthrene derivatives, 3,6-diphenyl-9,10-bis-(4-tert-butylphenyl)phenanthrene (TphP, T1), 3,6-di(naphthalen-2-yl)-9,10-bis(4-tert-butylphenyl)phenanthrene (TnaP, T2), and 3,6-di(pyrene-1-yl)-9,10-bis(4-tert-butylphenyl)phenanthrene (TpyP, T3), are investigated in an acetonitrile:benzene (v:v = 1:1) solvent. Cyclic voltammetry (CV) of the three derivatives shows reversible reduction waves and less chemically reversible oxidation waves at low scan rates. The CV character becomes more reversible, and the stability of the radical cations increases as the conjugation of the substituent groups appended to the phenanthrene increases. This finding indicates that the radical ion stabilities in phenanthrene derivatives are drastically improved by increasing the conjugation of the substituent groups; thus, electrochemically stable radical ions can be obtained by introducing more conjugated groups to the phenanthrene center. Additionally, ECL is generated for all compounds by radical ion annihilation, and the ECL spectrum shows good agreement with the fluorescence emission, assigned as emission by the S-route. ECL efficiencies for radical ion annihilation are 0.004 for TphP, 0.16 for TnaP, and 0.25 for TpyP, respectively, and the ECL efficiency increases with the conjugation of the substituent groups appended to the phenanthrene increases. Radical ion annihilation produced by potential steps exhibits asymmetric ECL transients in which the cathodic ECL pulse is smaller than the anodic pulse due to the instability of the radical cation. These molecules can produce a stronger ECL, which can be observed by the naked eye in a lighted room, on reduction in the presence of a coreactant (benzoyl peroxide).

Arynes, generated in situ from ortho-silylaryl triflates, undergo ene reaction with alkynes possessing propargylic hydrogen in the presence of KF/18-crown-6 in THF at room temperature to give substituted phenylallenes. Various terminal and internal alkynes as well as different arynes can be used to give the corresponding phenylallenes in good to moderate yields. The reaction of alkyne without propargylic hydrogen gave an acetylenic C−H addition product (a phenylalkyne) and a dehydro Diels−Alder product (a phenanthrene).

In the presence of Co(PPh3)2I2, PPh3, water, and zinc powder, the reaction of alkynes (R1CCR2: R1 = Ph, R2 = Me (1a); R1 = Ph, R2 = Ph (1b); R1 = Et, R2 = Et (1c); R1 = Ph, R2 = (CH2)3OH (1d); R1 = CO2Et, R2 = Ph (1e); R1 = CO2Me, R2 = (CH2)4CH3 (1f); R1 = CO2Et, R2 = SiMe3 (1g)) with alkenes having an electron-withdrawing substituent (CH2=CHR: R = CO2Bu (2a), CN (2b), SO2Ph (2c) and CO2Me (2d)) proceeded smoothly in acetonitrile to give the corresponding reductive coupling products (R1HC=CR2CH2CH2R, 3a-j) in fair to excellent yields. This reductive coupling is highly regio- and stereoselective; only one isomer was observed for each reaction. The results of an isotope-labeling experiment using D2O (99%) to replace normal water for the reductive coupling of vinyl phenyl sulfone 2c with alkyne 1a revealed that the product is E-Ph(D)C=CMeCH2CH(D)SO2Ph deuterated at the olefinic proton and one of the protons of the alpha-methylene group in 84 and 96%, respectively. Possible mechanisms for this highly regio- and stereoselective ene-yne catalytic reaction are proposed.

A new class of substituted seven-membered lactones 3 were conveniently synthesized via cyclization of o-iodobenzyl alcohol 1 (o-IC(6)H(4)CH(2)OH) with various propiolates 2 (RC triple bond CCOOMe) in the presence of Ni(dppe)Br(2) and Zn powder in acetonitrile at 80 degrees C. The catalytic reaction is highly regio- and stereoselective affording seven-membered lactones in moderate to good yields. This methodology can be successfully extended to various substituted o-iodobenzyl alcohols. An intermediate 7 was obtained from the reaction of 1a with methyl 2-octynoate (2a) in the presence of Ni(dppe)Br(2) and Zn at room temperature. A mechanism involving an unusual E/Z isomerization of the carbon-carbon double bond of 7 prior to lactone formation is proposed to account for the catalytic reaction.

An efficient homogeneous catalyst consisting of K/sub 2/PtCl/sub 4/, SnCl/sub 4/, H/sub 2/O, and HCl dissolved in glacial acetic acid was developed for the water gas shift reaction, H/sub 2/O + CO reversible H/sub 2/ + CO/sub 2/. Requirements and features of the catalyst are: (1) no reaction takes place in the absence of the platinum chloride salt; (2) the omission of tin chlorides greatly diminishes catalytic activity, leading to decomposition and formation of a brown precipitate; (3) large excesses of the tin chlorides inhibit catalysis- e.g., at a tin/ platinum ratio of 300/1, no reaction occurs; (4) if acetic acid is replaced by water, only a trace of carbon dioxide is produced and a dark brown precipitate is obtained; (5) no catalysis occurs in the absence of either a strong protic acid or a chloride source. A mechanism involving the tin(II)/tin(IV) couple and a platinum species is proposed.

A more active homogeneous catalyst system for the water gas shift reaction which functions at low temperatures (