- Rhodium(I)-Catalyzed Sequential C(sp)-C(sp3) and C(sp3)-C(sp3) Bond Formation through Migratory Carbene Insertion
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A RhI-catalyzed three-component reaction of tert-propargyl alcohol, diazoester, and alkyl halide has been developed. This reaction can be considered as a carbene-involving sequential alkyl and alkynyl coupling, in which C(sp)-C(sp3) and C(sp3)-C(sp3) bonds are built successively on the carbenic carbon atom. The RhI-carbene migratory insertion of an alkynyl moiety and subsequent alkylation are proposed to account for the two separate C-C bond formations. This reaction provides an efficient and tunable method for the construction of all-carbon quaternary center.
- Xia, Ying,Feng, Sheng,Liu, Zhen,Zhang, Yan,Wang, Jianbo
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supporting information
p. 7891 - 7894
(2015/06/30)
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- Synthesis and characterization of fluorinated heterofluorenecontaining donor-acceptor systems
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Chemical Equation Presented A series of oligothiophene- perfluoro-9-heterofluorene donor-acceptor (DA) compounds was synthesized via a combination of nucleophilic aromatic substitution (SNArF) and palladium coupling reactions. These compounds are of interest as possible building blocks for materials with useful electron transport properties, since they possess relatively low LUMO energy levels of-3.3 to -3.6 eV (as determined by differential pulse voltammetry). The HOMO-LUMO energy gaps, as determined by UV-vis spectroscopy, range between 2.4 and 2.5 eV, and photoluminescence emission spectra reveal λems values in the range of 480-600 nm (corresponding to yellow-orange emission). Dilute solution-state photoluminescence quantum yields were significantly lower than those of the pure acceptor heterofluorenes (0.02-0.38 for the DA compounds vs ~1 for the pure acceptors), and notable solvatochromism in the fluorescence suggests emission from a charge-separated state. Theoretical calculations show that HOMO-level electron density is more localized on the thiophene fragment, while the LUMO level electron density is mostly associated with the electron-deficient portion of the molecule. Photovoltaic (PV) devices based on DA/poly-3-hexylthiophene (P3HT) blends exhibit improved performance over P3HT-only devices, suggesting the ability of these DA compounds to transport electrons in the solid state.
- Geramita, Katharine,Tao, Yuefei,Segalman, Rachel A.,Don Tilley
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body text
p. 1871 - 1887
(2010/07/02)
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- Ethynyl-1,2-benziodoxol-3(1H)-one (EBX): An exceptional reagent for the ethynylation of keto, cyano, and nitro esters
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Hot alkyne! The in situ generation of ethynyl-1,2-benziodoxol-3(1H)-one (EBX) from a silyl-protected reagent by using TBAF is reported. EBX displayed exceptional acetylene transfer ability onto stabilized enolates (see scheme), even at -78 □°C. The mild reaction conditions allowed the first ethynylation reactions of linear keto, cyano, and nitro esters in high yields to give all-carbon quaternary centers or non-natural amino acids after selective reduction of the nitro group.
- Gonzalez, Davinia Fernandez,Brand, Jonathan P.,Waser, Jerome
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supporting information; experimental part
p. 9457 - 9461
(2010/10/03)
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- Direct alkynylation of indole and pyrrole heterocycles
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Chemical Equitation Presentation Easy does it: The unique properties of benziodoxolone alkynyl periodinane l and gold catalysts have allowed the development of a high yielding, operationally simple (room temperature, no dry sol-vents or inert conditions, commercially available catalyst) reaction for the introduction of silylacetylenes on a large range of indole and pyrrole heterocycles with a wide range of functional groups (see scheme).
- Brand, Jonathan P.,Charpentier, Julie,Waser, Jerome
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supporting information; experimental part
p. 9346 - 9349
(2010/03/30)
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- Novel reactions of steric encumbered 1,4-dilithio-1,3-butadiene with group 14 electrophiles: Formation and structure of stable dihydroxygermole
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Reactions of 1,4-dilithio-1,3-butadiene 1 having bulky silyl ligands at the 1,4-positions with group 14 electrophiles were examined. Reactions of 1,4-dilithio-1,3-butadiene 1 with tetraethoxygermane gave diethoxygermole 5, which was hydrolyzed to give sta
- Saito, Masaichi,Nakamura, Michio,Tajima, Tomoyuki
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experimental part
p. 657 - 668
(2009/06/08)
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- Bulky trialkylsilyl acetylenes in the Cadiot-Chodkiewicz cross-coupling reaction
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Bulky trialkylsilyl-protected alkynes such as triethylsilyl (TES), tert-butyldimethylsilyl (TBS), and tri-isopropylsilyl (TIPS) acetylenes underwent the Cadiot-Chodkiewicz cross-coupling reaction with different bromoalkynes to form a variety of synthetically useful unsymmetrical diynes in good yields. The diyne alcohol 10 was transformed regio- and stereoselectively into enynes by hydrotelluration, carbometalation, and reduction reactions.
- Marino, Joseph P.,Nguyen, Hanh Nho
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p. 6841 - 6844
(2007/10/03)
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- Biphenyldialkylsilyl chlorides: Reagents for the formation of crystalline derivatives of small terminal alkynes
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Biphenyldimethylsilyl chloride (BDMS-Cl) and biphenyldiisopropylsilyl chloride (BDIPS-Cl) are readily prepared reagents for the introduction of the BDMS and BDIPS protecting groups onto small terminal alkynes, leading to stable, solid, and easily recrystallizable derivatives of these thermally unstable molecules.
- Anthony,Diederich
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p. 3787 - 3790
(2007/10/02)
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- Silicon-Directed Nazarov Reactions III. Stereochemical and Mechanistic Considerations
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The influence of remote substituents on the stereochemical outcome of electrocyclization in the silicon-directed Nazarov reaction has been examined.While the degree of stereocontrol was modest (ca. 3:1) the substituent in the major isomer (4,5 or 7-substi
- Jones, Todd K.,Denmark, Scott E.
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p. 2397 - 2411
(2007/10/02)
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