- Palladium-catalyzed C-H formylation of electron-rich heteroarenes through radical dichloromethylation
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A novel palladium-catalyzed C-H formylation of electron-rich N-, O-, and S-containing heteroarenes has been developed. The key to success is that the commercially available BrCHCl2 was used as a stoichiometric carbonyl source. Mechanistic investigations indicated that different from the known Reimer-Tiemann reaction, this net C-H formylation proceeded through an electrophilc radical-type path.
- Bao, Yan,Wang, Jian-Yong,Zhang, Ya-Xuan,Li, Yan,Wang, Xi-Sheng
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supporting information
p. 3147 - 3150
(2018/07/13)
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- Low Oxidation Potential Tetrathiafulvalene Analogues Based on 3,4-Dialkoxythiophene π-Conjugating Spacers
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Tetrathiafulvalene analogues involving dihexyloxythiophene (1), ethylenedioxythiophene (2), and bis(3,4-dihexyloxy-2-thienyl)ethylene (3) as conjugating spacer and diversely substituted at the 1,3-dithiole ring (R) have been synthesized. Electronic absorption spectra show the expected decrease of HOMO-LUMO gap when increasing the electron-releasing power of R or the length of the conjugating spacer. Cyclic voltammetry (CV) shows that whereas compounds 1 and 2 are reversibly oxidized into their cation radical and dication through two one-electron steps, for compounds 3 the dication is formed directly via a two-electron transfer. Comparison of the data for compounds 2 and 3 with those of their respective analogues based on thiophene and dithienylethylene shows that introduction of the electron-donating alkoxy groups at the 3 and 4 positions of the thiophene ring produces a 150-200 mV negative shift of the first redox potential (E°1). On the other hand, CV data for compounds 1 and 2 reveal several unusual features such as E°1 ≈ 0.10 V/SCE ranking among the lowest known to date and a Coulombic repulsion between positive charges in the dication larger than for the analogue π-donors based on unsubstituted thiophene. These results are interpreted by a major reorganization of the electronic distribution in the donor molecule due to alkoxy groups: the highest electron density moving from the 1,3-dithiole moiety toward the central thiophene ring.
- Akoudad, Said,Frere, Pierre,Mercier, Nicolas,Roncali, Jean
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p. 4267 - 4272
(2007/10/03)
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