Palladium-catalyzed multistep reactions involving ring closure of 2-iodophenoxyallenes and ring opening of bicyclic alkenes

[reaction: see text] An efficient ring closure of 2-iodophenoxy-, 2-iodobenzyloxy-, and 2-iodobenzylaminoallenes followed by ring opening of oxabenzonorbornadienes leading to the synthesis of 2-benzofuranyl, 1H-isochromenyl, or 1,2-dihydroisoquinoline methyl-1,2-dihydro-1-naphthalenol derivatives catalyzed by palladium complexes is described.     

A [Fe(CB6)] platform for binding of small molecules: Insights from DFT calculations

The viability of making [Fe(CB₆)L] (L = H₂, N₂, O₂, nitric oxide [NO^?, NO, and NO⁺], CO₂, and hydrocarbons [CH₄, C₂H₆, C₂H₄, and C₆H₆]) has been investigated by density functional theory (DFT) calculations. The complexes 2 – 18 are thermodynamically stable and may be synthesized. The small molecules are activated to some extent after complexation. Molecular orbital and ΔG calculation revealed that the molecular hydrogen and hydrocarbons can be chemically adsorbed and desorbed on [Fe(CB₆)] without any significant chemical modification and therefore [Fe(CB₆)] may serve as a storage material. The N₂, O₂, and nitric oxide (NO^?, NO, and NO⁺) can be activated using [Fe(CB₆)]. Proton, carbon, boron, and nitrogen NMR chemical shift calculation predicts drastic chemical shift difference before and after the complexation of [Fe(CB₆)] with small molecules. This new findings suggest that the CB₆^2? ligand‐based complex may provide several applications in the future. © 2012 Wiley Periodicals, Inc.     

Structural and solvent dependence of superexciplex

In this paper, we show that a few coumarin dye solutions exhibit dual amplified spontaneous emission (ASE) spectra under pulsed laser excitation, though all these solutions exhibit only one fluorescence band under steady-state conditions. The anomalous band, appearing only in ASE spectra, had been attributed to the superexciplex--a new molecular species. This is made of two excited molecules and is obtainable only under pulsed laser excitation. This complex is different from the well known excimer or exciplex, wherein only one atom or molecule is in the excited state. The superexciplex is possible with the two polar excited molecules coming together to form an excited state association, with the solvent acting as some sort of bridge. With very polar dye molecules, such an association is possible even with the inert benzene acting as a bridge; otherwise solvents like ethyl acetate, with an oxygen atom, is necessary for the linkage.     

Highly regio- and chemoselective [2 + 2 + 2] cycloaddition of electron-deficient diynes with allenes catalyzed by nickel complexes: a novel entry to polysubstituted benzene derivatives

Diynes 1a-c [X(CH(2)Ctbd1;CCO(2)Me)(2): X = (CH(2))(2), 1a, X = CH(2), 1b and X = O, 1c] undergo [2 + 2 + 2] ene-diyne cycloaddition reactions with a variety of allenes (n-butylallene 2a, phenylallene 2b, (4-chlorophenyl)allene 2c, (4-bromophenyl)allene 2d, (3-methoxyphenyl)allene 2e, 1-naphthylallene 2f, cyclohexylallene 2g and cyclopentylallene 2h) in the presence of Ni(dppe)Br(2) and Zn powder in CH(3)CN at 80 degrees C for 8 h to give the corresponding polysubstituted benzene derivatives 4a-l in good to excellent yields. Under similar reaction conditions, unsymmetrical diynes 5a-c (HCtbd1;CCH(2)XCH(2)Ctbd1;CCO(2)Me) react with allenes 2 to afford exclusively the corresponding meta-isomers 6a-g in 73-86% yields. The catalytic reaction is highly regioselective and completely chemoselective. This synthetic method is compatible with many functional groups such as Cl, Br, and OMe on the phenyl group of the allene moiety and an ether linkage in a diyne moiety. In this catalytic reaction, allenes are synthetically equivalent to terminal alkynes. Interestingly, unsymmetrical diyne 7 (MeCtbd1;C(CH(2))(4)Ctbd1;CCO(2)Me) undergoes 2:1 cocyclotrimerization with allenes 2a and 2g to afford the corresponding polysubstituted benzene derivatives 9a,b in 87% and 82% yields, respectively. A plausible mechanism involving a nickelacycloheptadiene intermediate is proposed to account for this nickel-catalyzed reaction.     

Reactions in the presence of organic phosphites,I: High temperature amidation in the absence of solvents

When reacted for periods of 5–10 min at temperatures of about 280–300°C in the presence of certain organic phosphites polymers that contain available carboxy and aliphatic amine groups undergo amidation. This reaction can increase the molecular weight of many aliphatic polyamides by their self-reaction in an extruder. Block or graft copolymers can be formed by reacting polymers that contain aliphatic amines with others that contain carboxyl. Studies of model compounds in the companion article (II) indicate that polymerization proceeds through an diaryloxy or dialkoxy amino phosphine intermediate to produce amide bonds and disubstituted phosphite reaction by-products. In the absence of primary amines in the reaction mixture an ester is slowly formed from the carboxyl end group of the polymer and the oxysubstituent of the phosphite. In no case was a phosphorus-containing mixed anhydride detected. The mechanistic identity of the low temperature reactions in article II and the high temperature reactions in this article has not been proved conclusively, however.     

Palladium-catalyzed allylalkynylation of benzynes: a highly efficient route to substituted 1-allyl-2-alkynylbenzenes

Benzynes, generated in situ from 2-(trimethylsilyl)aryl triflates and cesium fluoride, undergo allylalkynylation with allylic chlorides and alkynylstannanes in the presence of palladium catalyst to give 1-allyl-2-alkynylbenzenes in good to excellent yields. [reaction: see text]     

Excimer state of a conjugate polymer (MEH-PPV) in liquid solutions

The conjugated polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is an important electrooptical material, which is useable as an excellent laser media. In this paper, we present the absorption and fluorescence spectral characteristics of MEH-PPV in a few organic solvents. The paper shows that MEH-PPV exists in an excimeric state in benzene, and that the laser action as shown here arises from a liquid excimeric state.     

Ruthenium-catalyzed ortho-alkenylation of aromatic ketones with alkenes by C-H bond activation

A ruthenium-catalyzed chelation-assisted C-H bond activation of aromatic ketones and the reaction with olefins to provide Heck-type products in good to excellent yields with a high regio- and stereoselective manner is described.