Facile synthesis of BINOL in the absence of solvent

Article abstract of DOI:10.1081/SCC-120004859

A new synthesis of BINOL is reported, which proceeds by the oxidation of 2-naphthol by iron(III) chloride when the two reagents are co-adsorbed on alumina. The method allows easy isolation of the product in high yield and in a high state of purity and does not require the use of specialized catalysts or large volumes of high-boiling organic solvents. Some derivatives of BINOL can also be prepared by this method.

Full text of DOI:10.1081/SCC-120004859

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FACILE SYNTHESIS OF BINOL IN THE ABSENCE OF
SOLVENT
a
a
Brian E. Love & Robert A. Bills
a
Department of Chemistry , East Carolina University , Greenville, NC, 27858, U.S.A.
Published online: 16 Aug 2006.
To cite this article: Brian E. Love & Robert A. Bills (2002) FACILE SYNTHESIS OF BINOL IN THE ABSENCE OF SOLVENT, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:13, 2067-2073, DOI:
10.1081/SCC-120004859
To link to this article: http://dx.doi.org/10.1081/SCC-120004859
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SYNTHETIC COMMUNICATIONS, 32(13), 2067–2073 (2002)
FACILE SYNTHESIS OF BINOL IN THE
ABSENCE OF SOLVENT
Brian E. Love* and Robert A. Bills
Department of Chemistry, East Carolina University,
Greenville, NC 27858, USA
ABSTRACT
A new synthesis of BINOL is reported, which proceeds by the
oxidation of 2-naphthol by iron(III) chloride when the two
reagents are co-adsorbed on alumina. The method allows easy
isolation of the product in high yield and in a high state of
purity and does not require the use of specialized catalysts
or large volumes of high-boiling organic solvents. Some
derivatives of BINOL can also be prepared by this method.
Key Words: BINOL; Oxidative coupling; Alumina; Synthesis
0
1
,1 -Bi-2-naphthol (BINOL) 2a has become an important chiral aux-
[
1]
iliary for asymmetric synthesis. Owing to its high degree of utility, a
number of synthetic approaches to this compound have been developed.
The most common methods of preparation involve transition metals as
catalysts or oxidants, though recently a method involving treatment of
[
2]
sodium 2-naphthoxide with bromine has also been reported.
*
Corresponding author. E-mail: loveb@mail.ecu.edu
067
2
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

2
068
LOVE AND BILLS
For the transition metal-catalyzed and -promoted reactions, the most
frequently employed metals are Fe(III) and Cu(II), though oxidations utiliz-
[
3]
[4]
ing Mn(III), Ti(IV) and V(V) have also been reported. In addition to
[5]
[
solution-phase oxidation with FeCl3 and Cu(II)/amine complexes,
6]
[7]
a number of metal complexes have been immobilized on solid supports
for use in this reaction. For example, FeCl adsorbed on alumina and also
3
[8]
[8,9]
[10]
silica gel, CuSO on alumina,
4
and Fe(III) and Cu(II)-doped zeolites
have all been used successfully. Although such supported reagents offer
some advantages with regard to ease of isolation of products, typically
high volumes of organic solvents have been used for this oxidation reaction.
[
8]
[9,10]
(
2
Between 10–20 mL of either xylene or chlorobenzene
-naphthol).
Solventless systems have also been investigated. Preparation of BINOL
by heating a mixture of 2-naphthol and Cu(OH)Cl-TMEDA (in the absence
per millimole of
[
11]
of solvent) has been reported, as has the heating of a powdered mixture of
[13]
[
12]
FeCl and 2-naphthol both with
3
and without
microwave irradiation.
Virtually all of these syntheses, however, (both solution phase and solvent-
free) produce BINOL contaminated by impurities which must be removed
[
14]
by either recrystallization or column chromatography.
Our past experience with performing oxidations on alumina in the
[15]
absence of solvent
led us to investigate the use of such conditions for
the oxidation of 2-naphthol to BINOL. In a typical experiment the metal
salt (either FeCl or CuSO ) and the 2-naphthol were co-adsorbed on the
surface of a solid support and then heated and stirred open to the air.
3
4
Oxidants prepared by adsorbing FeCl on basic, neutral, and acidic alumina
3
as well as silica gel were investigated and all gave BINOL, though the FeCl3
on slightly acidic alumina produced the best yields of product. Use of CuSO4
in place of FeCl also was effective, but did not appear to offer any signifi-
3
cant improvement over FeCl and tended to require longer reaction times
3
(
Figure 1).
Initially the 2-naphthol and FeCl were co-adsorbed on the alumina
3
by addition of a solution of the two reagents in methanol to the alumina,
followed by removal of the methanol under reduced pressure. Considerable
reaction appeared to be occurring in solution, however, prior to evaporation
of the solvent. Better yields of BINOL were obtained when the FeCl was
3
first deposited on the alumina by evaporation of an acetone solution (under
reduced pressure) followed by deposition of the 2-naphthol by evaporation
of a dichloromethane solution. The mixture obtained was placed briefly
under high vacuum to remove residual solvent, then stirred open to the air.
The formation of product was complete after approximately
ꢀ
30–45 min of heating at 90–100 C, the BINOL being obtained in crude
yields typically between 80–95%. Lower reaction temperatures could be used,

FACILE SYNTHESIS OF BINOL
2069
Figure 1. Oxidative coupling of 2-naphthol and derivatives.
but required longer reaction times and did not result in any improvement of
yield. Brief treatment of the alumina with acidic solutions of either acetone
or methanol was found to aid in the removal of BINOL from the alumina,
with phosphoric acid in methanol being the most effective washing solution.
The product was obtained in a high state of purity (as evidenced by melting
point and NMR analysis) though treatment with activated carbon was
sometimes necessary to remove highly colored impurities.
In contrast to most previously reported methods, BINOL of high
purity could be obtained without need of recrystallization or chromatog-
ꢀ
[9]
raphy. For example, crude product of melting point 213–214 C (lit.
ꢀ
214–216 C) has been obtained by our method in 94% yield. Treatment of
this sample with activated carbon gave product of melting point
ꢀ
2
15–215.5 C in 78% overall yield (see Table and Experimental section).
Replacement of the methanolic solution of phosphoric acid with an aqueous
solution prepared by dissolving 2 mL of 85% H PO in 40 mL water allowed
3
4
ꢀ
isolation of an off-white product of melting point 214–216 C directly (with-
out need of activated carbon treatment) though the yield was decreased to
64%. The reaction has been run on double the scale listed in the experi-
mental procedure, giving somewhat improved results (96% yield of product
ꢀ
with a melting point of 214–215 C before treatment with activated carbon,
and 89% yield of product after charcoal treatment with a melting point of
ꢀ
215–215.5 C). Stirring this larger reaction with a magnetic stirbar was more
problematic, however (Table 1).
Oxidative coupling of substituted 2-naphthols 1b and 1c by this
method has produced the corresponding binaphthols 2 in similarly high
yield (see Table). Significant yields of pure product were not obtained,
however, from attempts to couple naphthols which lacked appreciable

2
070
LOVE AND BILLS
Table 1. Product Yields and Melting Points
Crude Product Purified Product
ꢀ
ꢀ
ꢀ
Compound Yield (%) M.P. ( C) Yield (%) M.P. ( C) M.P. ( C) Lit. (9)
2
2
2
a
b
c
94
86
95
213–214
193–194
273–275
78
79
92
215–215.5
197–198
277–278
214–216
208–209
276–277
solubility in dichloromethane, such as 2,3-dihydroxynaphthalene, 2,7-dihy-
droxynaphthalene and 3-hydroxy-2-naphthoic acid. (Solubility in dichloro-
methane is beneficial for the deposition of the naphthol on the alumina
without concomitant dissolution of iron chloride already on the surface,
and also serves as an indicator of product solubility in dichloromethane,
which assists in the removal of the product from the alumina).
Recycling the alumina used in the experiment has been examined
briefly. Alumina used in one coupling of 2-naphthol was regenerated by
washing it with saturated sodium bicarbonate followed by methanol and
removal of the solvent under high vacuum. Use of this alumina in a sub-
ꢀ
sequent experiment produced BINOL of melting point 204–205 C in 82%
yield. (More drastic reductions in yield were observed if the alumina was not
washed with sodium bicarbonate).
In summary, a quick and operationally very simple procedure for the
oxidation of 2-naphthol to BINOL has been developed which is applicable
to the synthesis of substituted binaphthols. The products are obtained in
high yield and generally high states of purity. This method allows easy
isolation of the product and does not require the use of specialized catalysts,
large volumes of high-boiling solvents, or tedious purification procedures.
EXPERIMENTAL
0 0
,1 -Binaphthalene-2-2 -diol (2a)
1
A 3.94 g (14.6 mmol) sample of FeCl Á 6H O was dissolved in 40 mL
3
2
[
16]
acetone and added to 15.02 g of slightly acidic alumina. The solution was
stirred, then the solvent removed under reduced pressure. A 2.10 g
(
added to the FeCl /alumina mixture, stirred, and once again the solvent
14.6 mmol) sample of 2-naphthol was dissolved in 40 mL of CH Cl ,
2 2
3
removed under reduced pressure. The solid mixture was stirred and

FACILE SYNTHESIS OF BINOL
2071
ꢀ
heated at 90 C for 30 min open to the air. The mixture was allowed to cool
to room temperature then stirred for 5 min with a mixture of 10 mL 85%
H PO and 30 mL MeOH. The alumina was removed by suction filtration,
3
4
and the precipitate washed with several portions of CH Cl . The combined
2
2
filtrates were washed with water (50, 25, 25 mL), followed by 25 mL of
saturated NaCl solution. The organic layer was dried (MgSO ) and the
4
solvent removed under reduced pressure to give 1.95 g (93.6%) of crude
ꢀ
product (m.p. 213–214 C) as a brown solid. The crude product was dis-
solved in 70 mL of CH Cl and stirred with approx. 4.5 g of activated
2
2
carbon for one minute. The solution was suction filtered through celite,
the filtrate dried (MgSO ) and the solvent removed under reduced pressure
4
to give 1.63 g (78.3% overall) of purified product as an off-white solid, m.p.
ꢀ
ꢀ
2
7
15–215.5 C (lit. (9) 214–216 C). NMR (CDCl ) d 7.99 (d, J ¼ 8.8 Hz, 2H),
3
.91 (d, J ¼ 7.5 Hz, 2H), 7.5–7.1 (m, 8H), 5.06 (s, 2H).
0
0
0
6
-6 -Dibromo-1,1 -binaphthalene-2,2 -diol (2b)
Prepared analogously to that described for 2a. NMR (CDCl ) d 8.05
3
(
5
s, 2H), 7.90 (d, J ¼ 9.0 Hz, 2H), 7.4–7.3 (m, 4H), 6.96 (d, J ¼ 8.7 Hz, 2H),
.05 (s, 2H).
0
0
0
3
,3 -Bis(methoxycarbonyl)-1,1 -binaphthalene-2,2 -diol (2c)
Prepared analogously to that described for 2a. NMR (CDCl ) d 8.69
3
(
s, 2H), 7.90 (s, 2H), 7.4–7.0 (m, 8H), 4.05 (s, 6H).
Methyl 3-Hydroxy-2-naphthoate (1c)
A 1.07 g (5.7 mmol) sample of 3-hydroxy-2-naphthoic acid was dis-
solved in 20 mL methanol, followed by addition of 5 drops of conc.
H SO . The solution was heated at reflux for 21 h, then cooled to room
temperature and diluted with 50 mL ether. The solution was washed with
2
4
water (2 ꢁ 25 mL) and saturated NaHCO (25 mL). The organic layer was
3
dried (MgSO ) and the solvent removed under reduced pressure to give
4
ꢀ
1
(
.03 g (89.5%) of product as a light yellow solid, m.p. 71–72 C (lit. (17)
ꢀ
75–76 C). NMR (CDCl ) d 10.44 (s, 1H), 8.49 (s, 1H), 7.80 (d, J ¼ 8.1 Hz,
3
1
2
H), 7.69 (d, J ¼ 8.4 Hz, 1H), 7.50 (dd, J ¼ 6.6 Hz, 6.6 Hz, 2H), 7.5–7.2 (m,
H), 4.03 (s, 3H).

2
072
LOVE AND BILLS
REFERENCES
1
. Rosini, C.; Franzini, L.; Raffaelli, A.; Salvadori, P. Synthesis and
Applications of Binaphthylic C -Symmetry Derivatives as Chiral
2
Auxiliaries in Enantioselective Reactions. Synthesis 1992, 503.
. Holy, P.; Belohradsky, M.; Zavada, J. A Novel One-Pot Conversion of
2
0
0
2-Naphthols into 1,1 -Binaphthalene-2,2 -diols. Synth. Commun. 1996,
26, 2597.
3
. Dewar, M.J.S.; Nakaya, T. Oxidative Coupling of Phenols. J. Am.
Chem. Soc. 1968, 90, 7134.
. Doussot, J.; Guy, A.; Ferroud, C. Selective Synthesis of 1,1 -
0
4
Binaphthalene Derivatives by Oxidative Coupling with TiCl4.
Tetrahedron Lett. 2000, 41, 2545.
. Hwang, D.-R.; Chen, C.-P.; Uang, B.-J. Aerobic Catalytic Oxidative
5
6
7
Coupling of 2-naphthols and Phenols by VO(acac) . Chem. Commun.
2
1999, 1207.
. Deussen, H.-J.; Frederiksen, P.; Bjørnholm, T.; Bechgaard, K. A
0
0
Facile Large Scale Preparation of Racemic 2,2 -Dihydroxy-1,1 -
binaphthyl. Org. Prep. Proced. Int. 1996, 28, 484.
. (a) Smrcina, M.; Polakova, J.; Vyskocil, S.; Kocovsky, P. Synthesis of
Enantiomerically Pure Binaphthyl Derivatives. Mechanism of the
Enantioselective, Oxidative Coupling of Naphthols and Designing a
Catalytic Cycle. J. Org. Chem. 1993, 58, 4534; (b) Noji, M.;
Nakajima, M.; Koga, K. A New Catalytic System for Aerobic
Oxidative Coupling of 2-Naphthol Derivatives by the Use of CuCl-
Amine Complex: A Practical Synthesis of Binaphthol Derivatives.
Tetrahedron Lett. 1994, 35, 7983; (c) Nakajima, M.; Miyoshi, I.;
Kanayama, K.; Hashimoto, S.; Noji, M.; Koga, K. Enantioselective
Synthesis of Binaphthol Derivatives by Oxidative Coupling of Naphthol
Derivatives Catalyzed by Chiral Diamine-Copper Complexes. J. Org.
Chem. 1999, 64, 2264.
8
. Li, T.-S.; Duan, H.-Y.; Li, B.-Z.; Tewari, B.; Li, S.-H. Novel Oxidative
0
Coupling of 2-naphthols to 1,1 -bi-2-naphthols Catalyzed by Solid
Lewis Acids using Atmospheric Oxygen as Oxidant. J. Chem. Soc.
Perkin Trans. 1 1999, 291.
. (a) Sakamoto, T.; Yonehara, H.; Pac, C. Efficient Oxidative Coupling of
9
2-NaphtholsCatalyzedbyAlumina-SupportedCopper(II)SulfateUsing
Dioxygen as Oxidant. J. Org. Chem. 1994, 59, 6859; (b) Sakamoto, T.;
Yonehara, H.; Pac, C. Catalytic Activities of CuSO /Al O in
4
2
3
Dehydrogenation of Arenes by Dioxygen. J. Org. Chem. 1997, 62, 3194.
0. Armengol, E.; Corma, A.; Garcia, H.; Primo, J. A Highly Selective
1
0
Synthesis of 1,1 -Bi-2-naphthol by Oxidative Coupling of Naphthol on

FACILE SYNTHESIS OF BINOL
2073
Mesoporous Fe, Cu/MCM-41 Aluminosilicates. Eur. J. Org. Chem.
999, 1915.
1. Toda, F.; Tanaka, K.; Iwata, S. Oxidative Coupling Reactions of
1
1
Phenols with FeCl in the Solid State. J. Org. Chem. 1989, 54, 3007.
3
1
2. Nakajima, M.; Hashimoto, S.; Noji, M.; Koga, K. Aerobic Oxidative
Coupling of 2-Naphthol Derivatives Catalyzed by a Copper-Amine
Complex without Solvent. Chem. Pharm. Bull. 1998, 46, 1814.
1
3. Villmin, D.; Sauvaget, F. Dry Synthesis Under Microwave Irradiation:
A Rapid and Efficient Coupling of Naphthols. Synlett 1994, 435.
4. Product obtained by the procedure described in reference 9 could be
purified simply by treatment with active carbon, but the experimental
procedure is tedious (formation of product typically requires heating
1
ꢀ
dilute chlorobenzene solutions for 8 h at 140 C with continuous bub-
bling of air through the mixture).
15. Love, B.; Nguyen, B. Oxidation of Alcohols by Bromine on Alumina.
Synth. Commun. 2000, 30, 963.
1
1
6. Fluka type 506 C, Brockman activity 1, pH 6 for aqueous suspension.
7. Dictionary of Organic Compounds, 6th Ed.; Champman and Hall:
London, 1996; Vol. 4, 3742.
Received in the USA July 24, 2001