Asymmetric catalysis of homo-coupling of 3-substituted naphthylamine and hetero-coupling with 3-substituted naphthol leading to 3,3′-dimethyl-2, 2′-diaminobinaphthyl and -2-amino-2′-hydroxybinaphthyl

Article abstract of DOI:10.1002/chir.20731

Optically active 3,3′-dimethyl-2,2′-diamino-1,1′- binaphthyl (DM-DABN) and 3,3′-dimethyl-2-amino-2′-hydroxybinaphthyl (DM-NOBIN) derivatives were synthesized by Cu-(-)-sparteine complex-catalyzed enantioselective homo- and hetero-coupling of 2-naphthylami

Full text of DOI:10.1002/chir.20731

CHIRALITY 22:224–228 (2010)
Asymmetric Catalysis of Homo-Coupling of 3-Substituted
Naphthylamine and Hetero-Coupling with 3-Substituted
Naphthol Leading to 3,30-Dimethyl-2,20-diaminobinaphthyl
and -2-amino-20-hydroxybinaphthyl
*
YUKINORI YUSA, ISAO KAITO, KATSUHIRO AKIYAMA, AND KOICHI MIKAMI
Department of Applied Chemistry, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8552, Japan
ABSTRACT
Optically active 3,30-dimethyl-2,20-diamino-1,10-binaphthyl (DM-DABN)
and 3,30-dimethyl-2-amino-20-hydroxybinaphthyl (DM-NOBIN) derivatives were synthe-
sized by Cu-(2)-sparteine complex-catalyzed enantioselective homo- and hetero-coupling
of 2-naphthylamine, respectively. The difference in enantioselectivity was observed by
C
VV
changing the concentration of oxygen. Chirality 22:224–228, 2010.
2009 Wiley-Liss, Inc.
KEY WORDS: copper; sparteine; asymmetric; naphthylamine; homocoupling; hetero-
coupling; oxidative coupling; NOBIN; DABN
INTRODUCTION
NMR was expressed in parts per million downfield from
tetramethylsilane as an internal standard (d 5 0) in
CDCl3. Chemical shifts of 13C NMR were expressed in
parts per million downfield from CDCl3 as an internal
standard (d 5 77.0) in CDCl3. High performance liquid
chromatographic (HPLC) was conducted on JASCO
PU-980, LG-980-02, DG-980-50, and CO-966 instrument
equipped with model UV-975 spectrometers as an ultra vio-
let light. Peak areas were calculated by JASCO-BORWIN
(Windows NT) as an automatic integrator. DAICEL Chem-
ical AS, OD, OD-H, AD-H, and OJ-H were used as chiral
columns. Optical rotations were measured on a JASCO
DIP-370.
3-Methyl-2-naphthylamine was prepared from 3-amino-2-
naphthoic acid purchased from Aldrich Chemical Co.
(80%) by following procedure. Dichloromethane (anhy-
drous), acetonitrile (anhydrous), and xylene (anhydrous)
were purchased from Kanto Chemical Co. Dimethylsulfox-
ide was freshly distilled over CaH2. Red-Al1, copper(I)
iodide, 3-amino-2-naphthoic acid (80%), methyl 3-hydroxy-
2-naphthoate, and (2)-sparteine were purchased from
Aldrich Chemical Co. without further purification.
The mechanism of dioxygen (O2) activation in Cu-based
oxidases has attracted much attention because of its bio-
logical importance and potential application in industrial
redox processes.1 Here, we report the first example of
Cu-catalyzed enantioselective homo- and hetero-oxidative
coupling of 3-methyl-2-naphthylamine to give 3,30-dimethyl-
2,20-diamino-1,10-binaphthyl (DM-DABN) and 3,30-dimethy-
lated 2-amino-20-hydroxy-1,10-binaphthyl (DM-NOBIN) deriv-
atives, respectively.
DM-DABN is an effective enantio-discriminating reagent
as a chiral controller or asymmetric activator/deactivator of
racemic catalysts.2–10 In spite of the utility, synthetic methods
for DM-DABN have been quite limited so far. We have
reported enantio-resolution of racemic DM-DABN with a
chiral BINAP-Ru complex.6 However, our resolution method
is expensive. Furthermore, enantio-resolution methods
reported for DABN were found to be not applicable to race-
mic DM-DABN. Therefore, an enantioselective method to
synthesize 3,30-disubstituted DABN derivatives has been
strongly demanded. We thus focus on the copper-catalyzed
asymmetric oxidative couplings of 3-substituted 2-naphthyla-
mine as catalytic asymmetric routes not only to 3,30-disubsti-
tuted DABN but also to 3,30-disubstituted NOBIN derivatives,
in relation to biological Cu-based oxidases.1 There have been
many examples of Cu-catalyzed enantioselective homo- and
hetero-coupling of 2-naphthylamine and homo-coupling of
(3-substituted) 2-naphthol.11–25 In contrast, there has been no
successful example of catalytic enantioselective homo- and
hetero-coupling of 3-substituted 2-naphthylamine (1).19
Typical Procedure for the Synthesis of DM-DABN
by Oxidative Homo-Coupling Reaction
Under argon atmosphere, to the solution of CuI (1.9 mg,
0.01 mmol) in anhydrous CH3CN/CH2Cl2 (1/1, 1.0 ml)
was added (2)-sparteine (2.3 mg, 0.01 mmol). The reac-
tion mixture was allowed to stir for 30 min at room temper-
ature. 3-Methyl-2-naphthylamine (31.4 mg, 0.2 mmol) was
*Correspondence to: Koichi Mikami, Department of Applied Chemistry,
Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8552, Japan.
E-mail: mikami.k.ab@m.titech.ac.jp
Received for publication 29 July 2008; Accepted 25 February 2009
DOI: 10.1002/chir.20731
EXPERIMENTAL
General
1H NMR and 13C NMR were measured on Varian Gem-
Published online 30 April 2009 in Wiley InterScience
1
ini 2000 (300 MHz) spectrometers. Chemical shift of H (www.interscience.wiley.com).
C
VV
2009 Wiley-Liss, Inc.

SYNTHESIS OF DM-DABN AND DM-NOBIN
225
TABLE 1. Ligands and Cu salts for asymmetric
homo-coupling of 3-methyl-2-naphthylamine (1)
added to the mixture, and oxygen was removed by freeze
deaeration twice. The reaction mixture was equipped with
argon balloon (Oxygen was gradually introduced to the
reaction mixture through balloon), and allowed to stir for
24 h at 408C. After stirring, the reaction was quenched by
H2O, extracted with CH2Cl2, dried over MgSO4, and con-
centrated under reduced pressure. The residue was puri-
fied by silica-gel chromatography (hexane/ethyl acetate 5
4/1) to give 3,30-dimethyl-2,20-diamino-1,10-binaphthyl.
Typical Procedure for the Synthesis of DM-NOBIN
Derivatives by Oxidative Hetero-Coupling Reaction
Entry
Cu salt
Ligand
Yield (%)a
ee (%)b
Under argon atmosphere, to the solution of CuI (1.9 mg,
0.01 mmol) in anhydrous CH3CN/CH2Cl2 (1/1, 1.0 ml)
was added (2)-sparteine (2.3 mg, 0.01 mmol). The reac-
tion mixture was allowed to stir for 30 min at room temper-
ature. Then 3-methyl-2-naphthylamine (15.7 mg, 0.1 mmol)
and 3-hydroxy-2-naphthoic acid methyl ester (20.2 mg, 0.1
mmol) were added, and oxygen was removed by freeze
deaeration twice. Then, the reaction mixture was equipped
with argon balloon (Oxygen was gradually introduced to
the reaction mixture through balloon), and allowed to stir
for 24 h at 408C. After stirring, the reaction was quenched
by H2O, extracted with CH2Cl2, dried over MgSO4, and
concentrated under reduced pressure. The residue was
purified by silica-gel chromatography (hexane/ethyl ace-
tate 5 4/1) to give the (S)-30-methyl-20-amino-2-hydroxy-
1,10-binaphthyl-3-carboxylic acid methyl ester.
1
2
3
4
5
6
7
8
9
Cul
Cul
Cul
Cul
Cul
3a (n 5 0)
3b (n 5 1)
3c (n 5 2)
(S,S)–4
(S,S)–5
21
38
trace
26
20
33
39
28
10
–
–
–
–
5
6
12
32
25
16
–
Cul
Cul
(S,S)–6
(–)–spartaine 7
(–)–spartaine 7
(–)–spartaine 7
(–)–spartaine 7
(–)–spartaine 7
(–)–spartaine 7
CuBr
CuCl
CuCl2
Cu(OTf)2
Cu(OAc)2
10
11
12
–
–
–
–
aYield of isolated product.
bDetermined by HPLC analysis.
3-Methyl-2-naphthylamine (1). To a solution of 2-
amino-3-naphthoic acid (80% purity, 12.1 g, 52 mmol) in xy-
lene (350 ml) was added Red-Al1(117 ml, 390 mmol) at
room temperature under argon atmosphere. After stirring
for 6 h at 1508C, the reaction mixture was cooled to ambi-
ent temperature and then Red-Al1(39 ml, 130 mmol) was
added again. After stirring for 18 h at 1508C, 20% KOH
was carefully added at 08C. The reaction mixture was fil-
tered with a pad of Celite1 and then the filtrate was
washed with 1 N KOH. The organic layer was concen-
trated under reduced pressure. The residue was purified
by silica-gel chromatography (hexane/ethyl acetate 5 4/1
to 3/1) and recrystallized from hexane/ethyl acetate to
give the titled product (75% yield). 1H NMR (300 MHz,
CDCl3) d 2.36 (s, 3H), 3.79 (br, 2H), 7.01 (s, 1H), 7.22 (t, J
5 7.5 Hz, 1H), 7.33 (t, J 5 7.5 Hz, 1H), 7.55 (s, 1H), 7.59
(d, J 5 8.1 Hz, 1H), 7.65 (d, J 5 8.1 Hz, 1H). 13C NMR (75
MHz, CDCl3) d 17.9, 108.6, 122.4, 125.3, 125.4, 127.0,
128.2, 128.7, 133.7, 143.4, 161.0.
(S)-30-Methyl-20-amino-2-hydroxy-1,10-binaphthyl-
3-carboxylic acid methyl ester (11). 1H NMR (300
MHz, CDCl3) d 2.46 (s, 3H), 3.65 (br, 2H), 4.07 (s, 3H),
6.93 (d, J 5 9.0 Hz, 1H), 7.13 (td, J 5 6.9, 1.5 Hz, 1H), 7.20
(td, J 5 6.9, 1.5 Hz, 1H), 7.32–7.39 (m, 2H), 7.71 (s, 1H),
7.74 (d, J 5 7.8 Hz, 1H), 7.91–7.95 (m, 1H), 8.70 (s, 1H),
10.69 (s, 1H). 13C NMR (75 MHz, CDCl3) d 18.4, 52.7,
114.4, 118.1, 122.2, 123.7, 124.2, 124.9, 125.5, 127.4, 127.5,
128.2, 129.1, 129.7, 132.7, 132.9, 137.3, 141.6, 154.3, 170.4.
HPLC (CHIRALCEL OD-H column, hexane/2-propanol 5
80/20, flow rate 0.7 ml/min, detection UV 5 254 nm) tR of
R-isomer 7.8 min, tR of S-isomer 9.8 min.
(S)-3,30-Dimethyl-2,20-diamino-1,10-binaphthyl (DM-
DABN) (2). 1H NMR (300 MHz, CDCl3) d 2.45 (s, 6H),
3.45 (br, 4H), 7.01 (d, J 5 8.1 Hz, 2H), 7.15 (t, J 5 7.5 Hz,
2H), 7.22 (t, J 5 7.5 Hz, 2H), 7.70 (s, 2H), 7.75 (d, J 5 8.1
(S)-2,20-Dihydroxy-1,10-binaphthyl-3,30-dicarboxylic
Hz, 2H). 13C NMR (75 MHz, CDCl3) d 18.4, 112.8, 122.4, acid dimethyl ester (12). The titled compound was
123.8, 125.2, 125.8, 127.3, 128.4, 128.9, 132.5, 142.1. HRMS prepared from 3-hydroxy-2-naphthoic acid methyl ester
(ESI-TOF), calcd for C22H21N2 [M 1 H]1: 313.1704, according to the procedure as described for 2,20-dihy-
Found: 313.1697. HPLC (CHIRALCEL OD-H column, droxy-1,10-binaphthyl-3,30-dicarboxylic acid dimethyl ester.
hexane/2-propanol 5 80/20, flow rate 0.7 ml/min, detec- 1H NMR (300 MHz, CDCl3) d 4.06 (s, 6H), 7.14–7.20 (m,
tion UV 5 254 nm) tR of R-isomer 12.1 min, tR of S-isomer 2H), 7.30–7.38 (m, 4H), 7.88–7.95 (m, 2H), 8.69 (s, 2H),
17.9 min.
10.8 (s, 2H). HPLC (CHIRALCEL AD-H column, hexane/
Chirality DOI 10.1002/chir

226
YUSA ET AL.
(ESI-TOF), calcd for C22H19N2O [M1H]1: 314.15449,
Found: 314.15450. HPLC (CHIRALCEL OD-H column,
hexane/2-propanol 5 80/20, flow rate 0.7 ml/min, detec-
tion UV 5 254 nm) tR of R-isomer 15.5 min, tR of S-isomer
20.0 min. [a]2D5 5 216.4 (c 5 0.50, CH2Cl2). 40% ee product
from (2)-sparteine.
TABLE 2. Oxygen effects on Cu-catalyzed oxidative homo-
coupling of 3-methyl-2-naphthylamine (1)
RESULTS AND DISCUSSION
For oxidative homo-couplings of 3-substituted 2-naph-
thylamine, a variety of ligands were examined for Cu com-
plexes (Table 1). The treatment of 3-methyl-2-naphtyl-
amine with a Cu catalyst generated from 10 mol % each of
CuI and a ligand provided DM-DABN (2) at 408C for 24 h
under argon balloon (Oxygen was gradually introduced to
the reaction mixture). The chelate ring effect of achiral tet-
ramethyl diamines 3a–c was examined. The product 2
was obtained in the case of five and six membered chelate
Cu complexes with ligands 3a and 3b (entries 1 and 2).
The ligand 3c for seven membered chelate did not provide
any desired product (entry 3). The focused library of chiral
diamines 4–7 forming five or six membered chelate were
then investigated (entries 4–7): Among all the diamines
examined, (2)-Sparteine 7 was found to provide the high-
est yield and enantioselectivity (39% yield, 32% ee).
Entry
O2 concentration
Yield (%)a
ee (%)b
1
Ar (No O2)
trace
21
39
–
20
32
32
2c
3
O2 (O2 balloon)
Ar (Ar balloon)
Ar (Ar balloon)
4d
50
aYields of Isolated product
bDetermined by HPLC analysis.
cThe reaction is finished at 6 h.
dIn the presence of 20 mol % catalyst and ligand.
2-propanol 5 90/10, flow rate 1.0 ml/min, detection UV 5
254 nm) tR of R-isomer 11.8 min, tR of S-isomer 20.4 min.
Various Cu salts were next investigated (entries 8–12).
(S)-3,30-Dimethyl-2-amino-20-hydroxy-1,10-binaphthyl In sharp contrast to CuI bearing I2 as a weakly coordinat-
(13). To a solution of 3-methyl-30-carboxylic acid methyl ing counteranion, other Cu(I) salts such as CuCl and CuBr
ester-2-amino-20-hydroxy-1,10-binaphthyl (900 mg, 2.52 resulted in lower yield and enantioselectivity (28% yield,
mmol) in xylene (40 ml) was added Red-Al1 (10 ml, 3.3 25% ee and 10% yield, 16% ee, respectively) (entries 8 and
mmol) at room temperature under argon atmosphere. Af- 9). Cu(II) salts such as CuCl2, Cu(OTf)2, and Cu(OAc)2
ter stirred for 18 h at 1508C, 20% KOH was added carefully did not provide any product in all cases (entries 10–12).
at 08C. The reaction mixture was filtered with Celite1 and
The change in catalytic activity of a Cu complex was
then the filtrate was washed with 1 N KOH. The organic confirmed by changing the concentration of oxygen (Ta-
layer was concentrated under reduced pressure. The resi- ble 2). The reaction did not proceed without oxygen in the
due was purified by silica-gel chromatography (hexane/ tightly closed Schlenk tube (entry 1). Although oxygen
ethyl acetate 5 5/1) and by recrystallization from hexane played a critical role for catalyst turnover, higher yield,
1
and ethyl acetate to give the product (yield 74%). H NMR and enantioselectivity were obtained under argon (low
(300 MHz, CDCl3) d 2.45 (s, 3H), 2.52 (s, 3H), 3.74 (br, concentration of oxygen) than under high concentration of
2H), 5.20 (s, 1H), 7.00 (d, J 5 8.4 Hz, 1H), 7.09 (d, J 5 8.4 oxygen (39% yield, 32% ee vs. 21% yield, 20% ee; entries 2
Hz, 1H), 7.14–7.28 (m, 3H), 7.32 (td, J 5 6.6 Hz, 1H), 7.75 vs. 3). The increase of catalyst loading up to 20 mol % pro-
(s, 1H), 7.76 (d, J 5 7.5 Hz, 2H), 7.81 (d, J 5 7.8 Hz, 1H). vided the desired product (2) in 50% yield (entry 4).
13C NMR (75 MHz, CDCl3) d 17.0, 18.3, 108.7, 114.1,
The formation of carbazole26 8 and diazabicyclo com-
122.7, 123.5, 123.6, 124.4, 125.0, 125.9, 126.3, 126.9, 127.4, pound 9 was also observed as by-products in 10% and 38%
128.3, 129.5, 129.7, 130.0, 132.0, 133.0, 143.2, 151.1. HRMS yields, respectively (Scheme 1). However, DM-DABN did
Scheme 1. Cu-catalyzed oxidative homo-coupling of 3-methyl-2-naphthylamine (1).
Chirality DOI 10.1002/chir

SYNTHESIS OF DM-DABN AND DM-NOBIN
227
Scheme 2. Cu-catalyzed enantioselective hetero-coupling reaction for DM-NOBIN.
not provide 8 and 9 under the reaction conditions, proving low concentration of oxygen (Scheme 2). The decrease in
that these by-products (8 and 9) were not derived from enantioselectivity in higher concentrations of oxygen was
DM-DABN.
also confirmed in the hetero-coupling reaction; lower enan-
The extension of the oxidative homo-coupling to the het- tioselectivity of 11 (23% ee) was observed in high concen-
ero-coupling of 3-methyl-2-naphthylamine (1) with 3-sub- trations of oxygen when compared with 50% ee obtained in
stituted 2-naphthol (10) was further investigated to afford lower concentrations of oxygen. The desired product (11)
3,30-disubstituted NOBIN derivatives. The treatment of was easily converted by Red-A1 to afford DM-NOBIN 13
1 with 10 in the presence of a catalytic amount of CuI and in 74% yield.
(2)-sparteine under argon balloon with a low concentra-
The varied activity and enantioselectivity of a Cu-sparte-
tion of oxygen provided the desired 3,30-disubstituted ine catalyst depending on the concentration of oxygen are
NOBIN (11) in 50% yield and 50% ee and a small amount interesting and might be explained as follows; The CuI-
of 3,30-disubstituted BINOL (12) with 39% ee in 24% yield. (2)-sparteine complex (A) reacts with oxygen to afford
The enantioselectivity was varied by changing the atmos- the side-on peroxo complex (B) and bis-l-oxo complex
phere from a high concentration of oxygen to argon with a (C) in equilibrium.27–31 These Cu complexes (B and C)
Fig. 1. Possible mechanisms of sparteine-Cu(II) and -Cu(III) complexes in equilibria.
Chirality DOI 10.1002/chir

228
YUSA ET AL.
14. Ding K, Guo H, Li X, Yuan Y, Wang Y. Synthesis of NOBIN deriva-
tives for asymmetric catalysis. Top Catal 2005;35:105–116.
would produce the hydroxo complex (D) as monomer or
dimer via ligand exchange with water releasing H2O2 or
two electron reduction. The complex (D) catalyzes the
homo- and hetero-coupling reactions.32 Therefore, yields
and enantioselectivities would be increased under argon
(low concentration of oxygen) rather than high concentra-
tion of oxygen (Fig. 1).
In summary, we have reported the first example of Cu-(2)-
sparteine complex-catalyzed homo- and hetero-coupling of
3-substituted 2-naphthylamine to synthesize 3,30-disub-
stituted DM-DABN and DM-NOBIN enantioselectively.
Interestingly, the higher concentration of oxygen would
lead the Cu catalyst to the less catalytically active form
with low enantioselectivity, though oxygen plays a critical
role for catalyst turnover.
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The authors thank Prof. M. C. Kozlowski (University of
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Chirality DOI 10.1002/chir