Methyltrioxorhenium-catalyzed aerobic oxidative coupling of 2-naphthols to binaphthols

Article abstract of DOI:10.1016/S0040-4039(03)00352-6

A variety of 2-naphthols have been selectively oxidized to their corresponding 1,1′-bi-2-naphthols in excellent yields with molecular oxygen using methyltrioxorhenium as catalyst.

Full text of DOI:10.1016/S0040-4039(03)00352-6

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 2655–2656
Methyltrioxorhenium-catalyzed aerobic oxidative coupling of
2-naphthols to binaphthols
Vishal B. Sharma, Suman L. Jain and Bir Sain*
Chemical and Biosciences Division, Indian Institute of Petroleum, Dehradun 248005, India
Received 13 January 2003; revised 31 January 2003; accepted 7 February 2003
Abstract—A variety of 2-naphthols have been selectively oxidized to their corresponding 1,1%-bi-2-naphthols in excellent yields
with molecular oxygen using methyltrioxorhenium as catalyst. © 2003 Elsevier Science Ltd. All rights reserved.
The methyltrioxorhenium (MTO)/hydrogen peroxide
oxidation system first reported by Herrmann and co-
workers1 in 1991 for epoxidation of olefins has proved
to be an efficient and versatile system for various
oxidation reactions.2 The important features of MTO
as a catalyst are its ease of synthesis, commercial
availability, stability in air and efficiency in acting as a
homogeneous oxidation catalyst for hydrogen peroxide
in both aqueous and organic solvents. Molecular oxy-
gen is an attractive oxidant and the development of
synthetic methodologies using molecular oxygen is a
rewarding goal both from economic and environmental
points of view.3 However, to the best of our knowledge
there is only one literature report which describes the
oxidation of triphenylphosphines to triphenylphosphine
oxides by molecular oxygen using methyltrioxorhenium
as the catalyst.4
oxidant have also been reported in the literature. Most
of these methods require longer reaction times and
complex preparations of the catalyst, leaving scope for
further improvement in the catalytic oxidative coupling
of 2-naphthols.
As part of our studies on oxidation with molecular
oxygen as the primary oxidant15 we report a simple and
convenient method for the oxidation of 2-naphthols 1
to their corresponding 1,1%-bi-2-naphthols 2 in excellent
yields by using molecular oxygen as the sole oxidant
and methyltrioxorhenium as the catalyst (Scheme 1).
The oxidation of various substituted 2-naphthols was
carried out with molecular oxygen in refluxing
chlorobenzene using methyltrioxorhenium as catalyst.16
All the substrates studied were converted smoothly and
selectively to their corresponding ortho–ortho coupled
products in excellent yields. These results are presented
in Table 1 and clearly indicate that 6-bromo-2-naphthol
was the most reactive and gave the highest yield of
coupled product while 3-(carboxy)-2-naphthol was
found to be the least reactive and gave only 20% yield
of the coupled product. The oxidative coupling of
phenol did not take place, but 2,4-dimethylphenol 3
was selectively oxidized to its ortho–ortho coupled
product 4 under similar reaction conditions (Scheme 2).
Oxidative coupling of 2-naphthols is an important syn-
thetic transformation as 1,1%-bi-2-naphthols are widely
used chiral inducers in synthetic organic chemistry.5 A
wide variety of stoichiometric methods using FeCl3,6
K3Fe (CN)6,7 Mn (acac)3
and Cu(II)–amine
8
complexes9 as oxidative coupling reagents have been
reported in literature for this transformation. However,
these methods suffer from drawbacks such as the use of
an expensive oxidant (AgCl), the production of copious
amounts of heavy metal wastes and the need for high
temperatures. Recently several catalytic methods using
chiral diamine–copper complexes,10 CuSO4/Al2O3,11
VO(acac)2,12 CuCl13 and mesoporous molecular sieves14
as the catalysts and molecular oxygen as the primary
Keywords: methyltrioxorhenium; 2-naphthols; 1,1%-bi-2-naphthols;
oxidation; molecular oxygen.
* Corresponding author. Tel.: +91-135-2660071, fax: +91-135-
2660202; e-mail: birsain@iip.res.in
Scheme 1.
0040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)00352-6

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V. B. Sharma et al. / Tetrahedron Letters 44 (2003) 2655–2656
Table 1. Methyltrioxorhenium catalyzed aerobic oxidation
(c) Dobler, C.; Mehltretter, G. M.; Sundermeier, U.; Beller,
M. J. Am. Chem. Soc. 2001, 122, 10289; (d) David, R. J.;
Pugsley, S. J.; Matthew, S. J. Am. Chem. Soc. 2001, 123,
7475; (e) Davis, S.; Drago, R. S. J. Chem. Soc., Chem.
Commun. 1990, 250.
of 2-naphtholsa
Entry
Naphthol 1
Reaction time (h)
Yield (%)b
1a
1b
R1=R2=R3=H
R1=Br;
12
10
92
95
4. James, Z. Z.; Espenson, J. H. J. Mol. Catal. A: Chem. 1995,
103, 87.
R2=R3=H
R1=R3=H;
R2=OCH3
5. For reviews, see: (a) Rosini, G.; Franzini, L.; Raffaelli, A.;
Salvadori, P. Synthesis 1992, 503; (b) Kagan, H. B.; Riant,
O. Chem. Rev. 1992, 92, 1007; (c) Hattori, K.; Yamamoto,
H. J. Org. Chem. 1992, 57, 3264; (d) Hattori, K.; Miyata,
M.; Yamamoto, H. J. Am. Chem. Soc. 1993, 115, 1151; (e)
Zhang, X.; Taketomi, T.; Yoshizumi, T.; Kumobayashi,
H.; Akutagawa, S.; Mashima, K.; Takaya, H. J. Am.
Chem. Soc. 1993, 115, 3318; (f) Kaupp, G. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 728; (g) Mikami, K.; Motoyama,
Y.; Terada, M. J. Am. Chem. Soc. 1994, 116, 2812.
6. Toda, F.; Tanaka, K.; Iwata, S. J. Org. Chem. 1989, 54,
3007.
1c
1d
1e
12
20
24
90
40
20
R1=R2=H;
R3=COOCH3
R1=R2=H;
R3=COOH
a Reaction conditions: 2-naphthol (1 mmol), methyltrioxorhenium (5
mol%) in chlorobenzene (5 ml) at reflux temperature under an
oxygen atmosphere.
b Isolated yields.
7. Feringa, B.; Wynberg, H. J. Org. Chem. 1981, 46, 2547.
8. Yamamoto, K.; Fukushima, H.; Okamoto, Y.; Hatada, K.;
Nakazaki, M. J. Chem. Soc., Chem. Commun. 1984, 1111.
9. Feringa, B.; Wynberg, H. Tetrahedron Lett. 1977, 18, 4447.
10. Nakajima, M.; Miyoshi, I.; Kanayama, K.; Hashimoto, S.
I. J. Org. Chem. 1999, 64, 2264.
11. (a) Sakamoto, T.; Yonehara, H.; Pac, C. J. Org. Chem.
1997, 62, 3194; (b) Hans-Juergen, D.; Klaus, M.; Gotthard,
W. Arch. Pharm. 1988, 321, 153.
12. Hwang, D. R.; Chen, C. P.; Uang, B. J. Chem. Commun.
Scheme 2.
1999, 1207.
13. Elvira, A.; Avelino, C.; Hermenegildo, G.; Jaime, P. Eur.
J. Org. Chem. 1999, 8, 1915.
14. Prasad, M. R.; Kamalakar, G.; Kulkarni, S. J.; Raghavan,
To evaluate the effect of solvents, the aerobic oxidation
of 2-naphthol was carried out under similar reaction
conditions by using different solvents: chlorobenzene,
acetonitrile, 1,2-dichloroethane and toluene. Chloroben-
zene was found to be most suitable solvent. The oxidative
coupling of 2-naphthols was found to be very slow at
room temperature and could be carried out more
efficiently in refluxing chlorobenzene.
K. V. J. Mol. Catal. A: Chem. 2002, 180, 109.
15. (a) Sharma, V. B.; Jain, S. L.; Sain, B. Tetrahedron Lett.
2003, 44, 383; (b) Jain, S. L.; Sain, B. Chem. Commun. 2002,
1040; (c) Jain, S. L.; Sain, B. J. Mol. Catal. 2001, 176, 101;
(d) Rao, T. V.; Sain, B.; Kumar, K.; Murthy, P. S. N.;
Prasada Rao, T. S. R.; Joshi, G. C. Synth. Commun. 1998,
28, 319; (e) Sain, B.; Murthy, P. S. N.; Rao, T. V.; Prasada
Rao, T. S. R.; Joshi, G. C. Tetrahedron Lett. 1994, 35, 5083;
(f) Rao, T. V.; Sain, B.; Murthy, P. S.; Prasada Rao, T.
S. R.; Jain, A. K.; Joshi, G. C. J. Chem. Res. (S) 1997, 300;
(g) Rao, T. V.; Sain, B.; Murthy, P. S. N.; Joshi, G. C.;
Prasada Rao, T. S. R. Stud. Surf. Sci. Catal. 1998, 113, 921.
16. Typical experimental procedure: To a stirred solution of
2-naphthol (144 mg, 1 mmol) in chlorobenzene (5 ml) was
added methyltrioxorhenium (12 mg, 5 mol%) and the
reaction mixture was refluxed for 12 h under an oxygen
atmosphere. The reaction progress was monitored by TLC
(SiO2). After completion of the reaction the solvent was
evaporated under reduced pressure and the residue was
dissolved in dichloromethane. The dichloromethane layer
was washed twice with water and dried over anhydrous
sodium sulphate followed by evaporation of the solvent.
The residue thus obtained was purified by column chro-
matography on silica gel using ethyl acetate/hexane (1:4)
as eluent. Evaporation of the solvent yielded 1,1%-bi-2-
naphthol (265 mg, 92%). Similarly other substituted 2-
naphthols were oxidized using this procedure and their
reaction times and yields are given in the Table. The
products were identified by comparing their physical and
spectral data with those of authentic compounds reported
in literature.
The mechanism of this reaction is not clear at this stage
and further studies in this direction are being carried out.
In summary, we have developed a catalytic aerobic
oxidation for the selective oxidative coupling of 2-naph-
thols to their corresponding 1,1%-bi-2-naphthols. The
present method describes the second example of a
methyltrioxorhenium catalyzed oxidation reaction using
molecular oxygen as the oxidant.
References
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