- Facile aromatic nucleophilic substitution (SNAr) reactions in ionic liquids: An electrophile-nucleophile dual activation by [Omim]Br for the reaction
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A facile aromatic nucleophilic substitution (SNAr) reaction in recyclable [Omim]Br under relatively mild conditions has been described. An electrophile-nucleophile dual activation by [Omim]Br is also discovered based on control experiments, 1H NMR and IR spectroscopies. This chemistry provides an efficient and metal-free approach for the generation of Caryl-X (XS, N, O) bonds, many of which are significant synthetic intermediates or drugs, making this methodology attractive to both synthetic and medicinal chemistry.
- Zhang, Xiao,Lu, Guo-Ping,Cai, Chun
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p. 5580 - 5585
(2016/10/21)
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- NMR and DFT studies on persistent carbocations derived from benzo[kl]xanthene, dibenzo[d,d′]benzo[1,2-b:4,3-b′]difuran, and dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran in superacidic media
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Persistent carbocations generated by the protonation of hetero-polycyclic aromatic compounds with oxygen atom(s) were studied by experimental NMR and density function theory calculations. Benzo[kl]xanthene (1), dibenzo[d,d′]benzo[1,2-b:4,3-b′]difuran (2), and dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran (3) were synthesized by the annulation of arenediazonium salts. Compound 1 in FSO3H-SbF5 (4:1)/SO2ClF and 3 in FSO3H-SbF5 (1:1)/SO2ClF ionized to 1aH+ with protonation at C(4) and to 3aH+ with protonation at C(6), and these cations were successfully observed by NMR at low temperatures. The density function theory calculations indicated that 1aH+ and 3aH+ were the most stable protonated carbocations and that 2 should ionize to 2aH+ with protonation at C(6). According to the changes in 13C chemical shifts (Δδ13C), the positive charge was delocalized into the naphthalene unit for 1aH+, into one benzo[b,d]furan unit for 2aH+, and into one benzo[b,d]furan unit for 3aH+. The most stable persistent cations derived from the title compounds, 1-3, were found to be 1aH+ with protonation at C(4), 2aH+ with protonation at C(6), and 3aH+ with protonation at C(6) by experimental and theoretical methods.
- Okazaki, Takao,Nakagawa, Madoka,Futemma, Takeshi,Kitagawa, Toshikazu
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supporting information
p. 107 - 111
(2016/02/03)
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