4330
P. Yan et al. / Tetrahedron 64 (2008) 4325e4331
3. Conclusion
drying in vacuo. The cross-coupling selectivity (X/Y/Z) of
1
the obtained polymer was estimated from the H NMR analy-
In conclusion, a catalytic amount of the Lewis acid, such as
Yb(OTf)3, can control the oxidative cross-coupling reaction
between 2-naphthol and 3-hydroxy-2-naphthoic acid deriva-
tives with the copper catalyst to selectively produce a C1 sym-
metrical BINOL, that is, the radical coupling reaction is
effectively controlled by the Lewis acid catalyst. This novel
binary catalyst system also produces poly(BINOL) with an
alternating copolymer structure. The yields of the cross-
coupling products, cross-coupling, and stereoselectivities were
significantly affected by the structures of both the copper
catalyst and Lewis acid.
sis of the hydroxyl protons. The unit ratio (5/6) was deter-
mined by the 1H NMR analysis of the polymer after
acetylation of the hydroxyl groups with an excess amount of
acetyl chloride and pyridine in CH2Cl2.10
4.4. Materials
Dry solvents, such as THF and CH2Cl2 (Kanto) were used
for the oxidative coupling reactions. The optically active
liagnds, (þ)PMP (TCI), (ꢁ)Sp (Sigma), Phbox (Aldrich),
and (R)Bnbox (Aldrich) were used as received. The achiral
copper complex, CuCl(OH)eTMEDA, was purchased from
TCI. Monomers, 5 and 6, were synthesized according to a
previously reported procedure.10
4. Experimental
4.1. General
Cross-coupling product was obtained from 1a and 2b
1
(Fig. 3). Mp 113.0e114.5 ꢂC; H NMR (500 MHz, CDCl3)
1
The H and 13C NMR spectra were measured by a Varian
8.73 (d, 1H, J¼1.8 Hz, aromatic), 8.08e7.82 (m, 4H, aromatic),
7.46e7.07 (m, 6H, aromatic), 5.31 (s, 1H, eOH), 5.22 (s, 1H,
eOH), 3.93 (s, 3H, eCH3); 13C NMR (125 MHz, CDCl3)
167.12, 154.73, 152.93, 136.02, 133.29, 132.74, 131.69,
131.43, 129.42, 128.46, 128.38, 127.59, 126.77, 125.39,
124.45, 124.11, 123.94, 118.57, 117.98, 111.53, 110.13,
52.21; IR (KBr, cmꢁ1) 3379, 2949, 1709, 1620, 1597, 1508,
1475, 1387, 1284, 1205, 1146; [a]2D5 ꢁ2 (c 0.8, THF) for
27% ee (R). Anal. Calcd for C22H16O4: C, 76.73; H, 4.68.
Found: C, 76.73; H, 4.63.
1
Unity Inova (500 MHz for H) or Mercury 200 (200 MHz for
1H) spectrometer. The infrared (IR) spectra were recorded by
a Horiba FT-720 spectrometer. The optical rotation was mea-
sured using a Jasco P-1010 polarimeter at 25 ꢂC. The circular
dichroism (CD) spectra were obtained with a Jasco J-720WI
apparatus. The high-performance liquid chromatography
(HPLC) analyses were performed by a Jasco 986-PU chro-
matograph equipped with a UV (Jasco 970-UV) detector at
room temperature. The size exclusion chromatography
(SEC) analyses were conducted by a Jasco PU-2080-Plus
equipped with a Jasco UV-2075-Plus UV detector with
KF-806L and KF-803L columns connected in series
(eluent¼THF, flow rate¼1.0 mL/min, calibration: polystyrene
standard).
Acknowledgements
This work was partially supported by Seki memorial foun-
dation for science.
4.2. General procedure for oxidative cross-coupling in the
presence of Lewis acid1
References and notes
1. Preliminary communication: Habaue, S.; Temma, T.; Sugiyama, Y.; Yan,
P. Tetrahedron Lett. 2007, 48, 8595e8598.
To a solution of 2-naphthols 1, 3-hydroxy-2-naphthoates 2,
and Yb(OTf)3, a mixture of CuCl and a diamine in THF
([1]0¼0.17 M) was added. After room temperature stirring un-
der an O2 atmosphere, the reaction mixture was diluted with
CHCl3 and then washed with 1 N HCl and brine. The organic
layer was dried over MgSO4. Subsequent filtration and con-
centration afforded the crude products. Purification was ac-
complished by silica gel column chromatography that
produced the BINOL derivatives.6,7
2. Brunel, J. M. Chem. Rev. 2005, 105, 857e897.
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4.3. Procedure for oxidative cross-coupling copolymerization
in the presence of Lewis acid
5. (a) Habaue, S.; Seko, T.; Okamoto, Y. Macromolecules 2003, 36, 2604e
2608; (b) Habaue, S.; Seko, T.; Isonaga, M.; Ajiro, H.; Okamoto, Y.
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A mixture of CuCl and ligand in THF ([CuCl]/[di-
amine]¼0.1:0.12) was stirred for 30 min under an O2 atmo-
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a polymer was isolated as the methanoleethyl acetatee1 N
HCl (1:3:0.2, v/v/v) insoluble fraction by centrifugation and
6. (a) Temma, T.; Habaue, S. Tetrahedron Lett. 2005, 46, 5655e5657; (b)
Temma, T.; Hatano, B.; Habaue, S. Tetrahedron 2006, 62, 8559e8563.
7. Habaue, S.; Takahashi, Y.; Temma, T. Tetrahedron Lett. 2007, 48, 7301e
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8. (a) Yamamoto, Y.; Onuki, S.; Yumoto, M.; Asano, N. J. Am. Chem. Soc.
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1999, 32, 163e171; (c) Srikanth, G. S. C.; Castle, S. L. Tetrahedron