C O M M U N I C A T I O N S
in these reactions (entries 4-10). Moreover, the products 7k and
7l obtained from 3-bromo- and 3-iodo-2-naphthols 3b and 3f,
respectively, can be converted to various C1-symmetric BINOLs
via a cross-coupling reaction.
substrate scope than the previously reported enantioselective cross-
coupling oxidation.3e,f,i,j Moreover, the present study’s disclosure
that the scope of the cross-coupling reaction is different from that
of the homocoupling is noteworthy. For example, the presence of
two C3 substituents is not essential for obtaining high enantiose-
lectivity in the oxidative coupling process if the less electron-
deficient naphthyl moiety has a C3 substituent, and 6-methoxycar-
bonyl-2-naphthol 4c, which cannot undergo a homocoupling
reaction under the present aerobic oxidation conditions, can undergo
a cross-coupling reaction. Investigation of the detailed stereochem-
ical course of this reaction is in progress.
Table 1. Asymmetric Oxidative Cross-Coupling of Various
2-Naphtholsa
1, air
3 + 4
8 5 + 6 + 7
toluene, 60 °C, 48 h
5
7
Acknowledgment. Financial support from Specially Promoted
Research (18002011) and the Global COE Program “Science for
Future Molecular Systems” from MEXT, Japan, is gratefully
acknowledged. H.E. is grateful for the JSPS Research Fellowships
for Young Scientists.
yield
(%)b
ee
(%)c
yield
(%)b
ee
(%)c
entry
X
Y
5/6/7d
1e
2-naphthyl Br
42
(5c)
34
90
52
(7d)
44
(7e)
52
(7f)
70
(7f)
65
(7g)
60
(7h)
68
(7i)
53
89
88
90
90
88
88
87
93
93
95
2:2:5
(3c)
PhCt
(3d)
Ph
(3a)
Ph
(3a)
Ph
(3a)
Ph
(4b)
Br
(4b)
2e
C
96
90
90
90
90
90
96
93
95
4:3:9
(5d)
3f
CO2Me 41
(5a)
CO2Me 25
2:0:5
Supporting Information Available: Experimental procedures,
spectral data for binaphthols, HPLC conditions, and crystallographic
data (CIF). This material is available free of charge via the Internet at
(4c)
4f,g
5f,g
2:0:11
2:0:15
1:0:6
(4c)
Ac
(4d)
CHO
(4e)
CN
(5a)
17
(5a)
20
(5a)
14
6f,g
References
(3a)
(1) For reviews of asymmetric catalysis with BINOL derivatives, see: (a)
Brunel, J. M. Chem. ReV. 2005, 105, 857–897. (b) Terada, M. Chem.
Commun. 2008, 4097–4112.
7g h Ph
,
1:trace:10
2:0:21
1:0:15
1:0:20
(3a)
TMSCt
(4f)
(5a)
8f,g
9f,i
C
CO2Me 10
(2) For catalysts possessing a chiral 3,3′-disubstituted binaphthyl scaffold, see:
(a) Connon, S. J. Angew. Chem., Int. Ed. 2006, 45, 3909–3912. (b) Akiyama,
T. Chem. ReV. 2007, 107, 5744–5758.
(3e)
Br
(3b)
I
(4c)
CO2Me
(4c)
CO2Me
(4h)
(4e)
7
(5a)
5
(5a)
(7j)
54
(7k)
50
(3) Selected reports on copper-catalyzed asymmetric oxidative coupling of
ˇ
2-naphthols: (a) Smrcˇina, M.; Pola´kova´, J.; Vyskocˇil, S.; Kocˇovsky´, P. J.
10f,i
ˇ
Org. Chem. 1993, 58, 4534–4538. (b) Smrcˇina, M.; Vyskocˇil, S.; Ma´ca,
B.; Pola´sˇk, M.; Claxton, T. A.; Abbott, A. P.; Kocˇovsky´, P. J. Org. Chem.
1994, 59, 2156–2163. (c) Nakajima, M.; Kanayama, K.; Miyashi, I.;
Hashimoto, S. Tetrahedron Lett. 1995, 36, 9519–9520. (d) Nakajima, M.;
Miyoshi, I.; Kanayama, K.; Hashimoto, S. J. Org. Chem. 1999, 64, 2264–
2271. (e) Li, X.; Yang, J.; Kozlowski, M. C. Org. Lett. 2001, 3, 1137–
1140. (f) Li, X.; Hewgley, J. B.; Mulrooney, C. A.; Yang, J.; Kozlowski,
M. C. J. Org. Chem. 2003, 68, 5500–5511. (g) Gao, J.; Reibenspies, J. H.;
Martell, A. E. Angew. Chem., Int. Ed. 2003, 42, 6008–6012. (h) Kim, K. H.;
Lee, D.-W.; Lee, Y.-S.; Ko, D.-H.; Ha, D.-C. Tetrahedron 2004, 60, 9037–
9042. (i) Temma, T.; Habaue, S. Tetrahedron Lett. 2005, 46, 5655–5657.
(j) Yan, P.; Sugiyama, Y.; Takahashi, Y.; Kinemuchi, H.; Temma, T.;
Habaue, S. Tetrahedron 2008, 64, 4325–4331.
(3f)
(7l)
a The coupling reactions were carried out in toluene with a 3/4 molar
ratio of 1:1 by using 1 (4 mol %) for 48 h on a 0.5 mmol scale under
aerobic conditions, unless otherwise mentioned. b Isolated yield. The
theoretical maximum (100%) yields of the cross-coupling and
homocoupling products correspond to the formation of 0.5 and 0.25
mmol of products, respectively. c Determined by HPLC analysis on a
chiral stationary phase column. d Molar ratio of respective BINOL
products. e The ee value of homocoupling product 6b was 18% ee. f No
homocoupling product derived from 4 was obtained. g Using 2 equiv of
4, with 3 added in three batches over 9 h. h A trace amount of the
homocoupling product derived from 4f was detected. i Run for 96 h
using 6 mol % 1 and 2 equiv of 4, with 3 added in three batches over
24 h.
(4) Selected reports on vanadium-catalyzed asymmetric oxidative coupling of
2-naphthols: (a) Chu, C.-Y.; Hwang, D.-R.; Wang, S.-K.; Uang, B.-J. Chem.
Commun. 2001, 980–981. (b) Hon, S.-W.; Li, C.-H.; Kuo, J.-H.; Barhate,
N. B.; Liu, Y.-H.; Wang, Y.; Chen, C.-T. Org. Lett. 2001, 3, 869–872. (c)
Barhate, N. B.; Chen, C.-T. Org. Lett. 2002, 4, 2529–2532. (d) Luo, Z.;
Liu, Q.; Gong, L.; Cui, X.; Mi, A.; Jiang, Y. Angew. Chem., Int. Ed. 2002,
41, 4532–4535. (e) Guo, Q.-X.; Wu, Z.-J.; Luo, Z.-B.; Liu, Q.-Z.; Ye, J.-
L.; Luo, S.-W.; Cun, L.-F.; Gong, L.-Z. J. Am. Chem. Soc. 2007, 129,
13927–13938. (f) Somei, H.; Asano, Y.; Yoshida, T.; Takizawa, S.;
Yamataka, H.; Sasai, H. Tetrahedron Lett. 2004, 45, 1841–1844. (g)
Takizawa, S.; Katayama, T.; Sasai, H. Chem. Commun. 2008, 4113–4122.
(5) Irie, R.; Masutani, K.; Katsuki, T. Synlett 2000, 1433–1436.
This concept can be successfully applied to the coupling between
the electron-rich and -poor 2-naphthols with a C3 substituent
(Scheme 4).
(6) (a) Matsushita, M.; Kamata, K.; Yamaguchi, K.; Mizuno, N. J. Am. Chem.
Soc. 2005, 127, 6632–6640. (b) Hewgley, J. B.; Stahl, S. S.; Kozlowski,
M. C. J. Am. Chem. Soc. 2008, 130, 12232–12233.
Scheme 4. Cross-Coupling of Two 3-Substituted 2-Naphthols
(7) Egami, H.; Katsuki, T. J. Am. Chem. Soc. 2009, 131, 6082–6083.
ˇ
(8) (a) Kocˇovsky´, P.; Vyskocˇil, S.; Smrcˇina, M. Chem. ReV. 2003, 103, 3213–
3245. (b) Shibasaki, M.; Matsunaga, S. Chem. Soc. ReV. 2006, 35, 269–
279.
(9) (a) Hovorka, M.; Gu¨nterova´, J.; Za´vada, J. Tetrahedron Lett. 1990, 31,
413–416. (b) Hovorka, M.; Za´vada, J. Tetrahedron 1992, 48, 9517–9530.
(10) In our previous report (ref 7), we proposed that complex 1 is a µ-oxo dimer
on the basis of its IR spectrum. However, its structure was revealed to be
a di-µ-hydroxo dimer by X-ray crystallography. For the X-ray crystal-
lography, see Figure S2.
In summary, we were able to propose a possible mechanism for
aerobic oxidative coupling of 2-naphthols using iron(salan) complex
1 as the catalyst on the basis of studies of the kinetics and the
relationship between product ee and catalyst ee for the coupling,
and this enabled us to establish a highly enantioselective aerobic
oxidative cross-coupling method for the preparation of C1-sym-
metric BINOLs. This cross-coupling reaction possesses a wider
(11) Puchot, C.; Samuel, O.; Dun˜ach, E.; Zhao, S.; Agami, C.; Kagan, H. B.
J. Am. Chem. Soc. 1986, 108, 2353–2357.
(12) The supplementary crystallographic data for 2 have been deposited with
The Cambridge Crystallographic Data Centre (CCDC) under entry code
CCDC 771569. These data can be obtained free of charge from the CCDC
(13) See the Supporting Information for details.
JA105442M
9
J. AM. CHEM. SOC. VOL. 132, NO. 39, 2010 13635