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chlorobenzenediazonium tetrafluoroborate (2c),[26] 4-iodobenzene-
diazonium tetrafluoroborate (2d),[24] 2-bromobenzenediazonium
tetrafluoroborate (2e),[27] 4-nitrobenzenediazonium tetrafluorobo-
rate (2 f),[24] 4-cyanobenzenediazonium tetrafluoroborate (2g),[26] 4-
acetylbenzenediazonium tetrafluoroborate (2h),[28] 4-methoxyben-
zenediazonium tetrafluoroborate (2i),[24] benzenediazonium tetra-
fluoroborate (2j).[28]
role-1-carboxylate (4 fi),[7] 2,5-dimethyl-4’-nitro-1,1’-biphenyl (4 fj),[35]
2,4,6-trimethyl-4’-nitro-1,1’-biphenyl (4 fk),[36] 2,4,6-trimethoxy-4’-
nitro-1,1’-biphenyl (4 fl),[37] 9-(4-nitrophenyl)anthracene (4 fm),[7]
2,5-bis(4-bromophenyl)furan (5aa).[38]
Characterization data for the new compounds
Preparation of a reduced form of polyaniline 1: A 300 mL round-
bottom flask with a stirring bar was charged with molecular nitro-
gen. To the flask were added polyaniline emeraldine base (3.0 g),
dry THF (45 mL), and hydrazine monohydrate (15 mL) at room tem-
perature. After stirring for overnight, degassed water (20 mL) was
added to the mixture. Then, the mixture was concentrated under
vacuum. Further degassed water (10 mL) was added to the mixture
again, and the mixture was concentrated under reduced pressure.
Toluene (20 mL) was added to the mixture, which was then con-
centrated under vacuum. During these concentration steps, care
was taken to avoid exposing the materials to the air. Finally, the
residue was dried at 1208C under vacuum to give a reduced form
of polyaniline 1 (2.8 g). Identification of the obtained polyaniline
1 was conducted by comparison with the data of UV/Vis/NIR spec-
trum reported in reference [29].
2-Methyl-5-(4-nitrophenyl)furan (4 fb): 1H NMR (400 MHz, CDCl3)
d=8.22 (d, J=9.2 Hz, 2H), 7.73 (d, J=9.2 Hz, 2H), 6.78 (d, J=
3.7 Hz, 1H), 6.16–6.14 (m, 1H), 2.41 ppm (brs, 3H); 13C NMR
(100 MHz, CDCl3) d=154.79, 150.28, 146.07, 136.87, 124.49, 123.41,
110.40, 108.95, 13.99 ppm; IR(KBr) n˜ =3128, 3103, 2919, 2430, 1607,
1598, 1544, 1503, 1440, 1417, 1386, 1330, 1288, 1207, 1109, 1065,
1027, 959, 921, 851, 787, 752, 691, 490 cmÀ1; HRMS (FAB) m/z: [M]+
calcd for C11H9NO3: 203.0582; found: 203.0582.
3,4-Dimethoxy-2-(4-nitrophenyl)thiophene
(4 fh):
1H NMR
(400 MHz, CDCl3) d=8.22 (d, J=9.2 Hz, 2H), 7.89 (d, J=9.2 Hz, 2H),
6.31 (s, 1H), 3.90 (s, 3H), 3.89 ppm (s, 3H); 13C NMR (100 MHz,
CDCl3) d=151.79, 146.32, 145.68, 139.92, 126.86, 124.21, 122.94,
97.17, 60.49, 57.51 ppm; IR(KBr) n˜ =3111, 3021, 2948, 1593, 1563,
1506, 1484, 1454, 1432, 1398, 1341, 1276, 1210, 1171, 1141, 1121,
1039, 1001, 941, 885, 849, 839, 756, 734, 714, 675, 542 cmÀ1; HRMS
(MALDI-TOF) m/z: [M]+ calcd for C12H11NO4S: 265.0409; found:
265.0403.
A representative procedure for method B (synthesis of 4 fa;
Scheme 2): A 20 or 50 mL two-necked flask with a stirring bar was
charged with molecular nitrogen. To the flask were added furan 3a
(320 mL, 4.4 mmol or 1.55 mL, 20 mmol, respectively) and a 5.5 mm
DMSO solution of a reduced form of polyaniline 1 (0.8 mL,
4.4 mmol or 3.6 mL, 20 mmol, based on aniline tetramer). Then,
a DMSO solution (3.2 mL or 14 mL) of 4-nitrobenzenediazonium
tetrafluoroborate 2 f (104 mg, 0.44 mmol or 474 mg, 2 mmol) was
added dropwise by using a syringe pump (50.8 mLhÀ1) at room
temperature. The reaction mixture was stirred for 30 min. The reac-
tion mixture was poured into a mixture of Et2O and water. The
aqueous layer was extracted with Et2O twice. The combined organ-
ic layer was washed with aqueous saturated NaHCO3 solution and
brine, dried with Na2SO4, and concentrated under reduced pres-
sure. The residue was purified by silica-gel column chromatogra-
phy (4:1 hexane/ethyl acetate) to give the product 4 fa (64.5 mg,
0.34 mmol, 77% or 299 mg, 1.58 mmol, 79%).
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific Re-
search on Innovative Areas “Advanced Molecular Transforma-
tions by Organocatalysts” from The Ministry of Education, Cul-
ture, Sports, Science and Technology, Japan (26105736).
Keywords: arylation
polyaniline · radical reactions
·
CÀC coupling
· cross-coupling ·
[1] For reviews, see: a) Redox Systems Under Nano-Space Control (Ed.: T.
Hirao), Springer, Heidelberg, 2006; b) T. Amaya, T. Hirao, Synlett 2011,
d) T. Hirao, T. Moriuchi, T. Amaya in Functionalized Redox Systems: Syn-
thetic Reactions and Design of p- and Bio-conjugates (Ed.: T. Hirao),
Springer, Amsterdam, 2015, pp. 51–109.
[4] Gomberg–Bachmann Reaction in Comprehensive Organic Name Reac-
tions and Reagents (Ed.: Z. Wang), Wiley, Hoboken, 2009, pp. 1248–
1251.
Kçnig, Angew. Chem. Int. Ed. 2014, 53, 725–728; Angew. Chem. 2014,
126, 743–747.
General experimental procedure (method B) for optimization of
the conditions and substrate scope: A 10 mL two-necked flask
with a stirring bar was replaced by molecular nitrogen. To the flask
were added arene 3 (1.1 mmol) and a 5.5 mm [D6]DMSO solution
of a reduced form of polyaniline 1 (0.2 mL, 1.1 mmol based on ani-
line tetramer). Then, a [D6]DMSO solution (0.8 mL) of arenediazoni-
um tetrafluoroborate 2 (0.11 mmol) and 1,3,5-tribromobenzene
(0.036 mmol) was added dropwise by using a syringe pump
(12.7 mLhÀ1) at room temperature. The reaction mixture was
stirred for 30 min. A sample was taken from the reaction mixture
and diluted by a factor of 10 with [D6]DMSO. The yields of prod-
ucts 4 was calculated based on the integral ratio in the 1H NMR
spectrum. Identification of the products 4 was conducted by com-
parison with the 1H NMR data reported previously (after isolation
of the product by preparative TLC, see the Supporting Informa-
tion): 2-(4-bromophenyl)furan (4aa),[6a] 2-(4-fluorophenyl)furan
(4ba),[30] 2-(4-chlorophenyl)furan (4ca),[6a] 2-(4-iodophenyl)furan
(4da),[31] 2-(2-bromophenyl)furan (4ea),[32] 2-(4-nitrophenyl)furan
(4 fa),[6a] 4-(furan-2-yl)benzonitrile (4ga),[6a] 1-(4-(furan-2-yl)phenyl)-
ethanone (4ha),[33] 2-(4-methoxyphenyl)furan (4ia),[6a] 2-phenylfur-
an (4ja),[6a] 1-(5-(4-nitrophenyl)furan-2-yl)ethanone (4 fc),[32] 5-(4-ni-
trophenyl)furan-2-carbaldehyde (4 fd),[7] 4-bromo-2-(4-nitrophenyl)-
furan (4 fe),[7] 2-(4-nitrophenyl)thiophene (4 ff),[7] 2-methyl-5-(4-ni-
trophenyl)thiophene (4 fg),[6a] tert-butyl 2-(4-nitrophenyl)-1H-pyr-
[8] D. Kalyani, K. B. McMurtrey, S. R. Neufeldt, M. S. Sanford, J. Am. Chem.
Chem. Eur. J. 2015, 21, 16427 – 16433
16432
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