Reactivity of naphthol towards nucleophiles in anodic oxidation

Article abstract of DOI:10.1016/S0040-4020(02)00829-3

Reactivity of the anodic oxidation of 4-methoxy-1-naphthol 1 in the presence of nucleophiles has been investigated. The reaction with electron-rich alkenic nucleophiles such as 1-methoxy-4-propenylbenzene 2 and isosafrole 3 gave a very high yield, whereas the reaction with dihydropyran 4 and dihydrofuran 5 gave a moderate yield, but with ethyl vinyl ether 6 gave a very low yield of the substituted dihydronaphthofuran derivatives 7-10 and 12, respectively. Unexpectedly, the glycosyl derivative 11 was preferentially produced rather than naphthofuran 10 upon using 5 as a nucleophile. In addition, the dimers 15 and 16 were obtained in moderate yield without addition of nucleophile to 1. The mechanism of the oxidation reactions including the [3+2] and [5+2] cycloaddition were discussed.

Full text of DOI:10.1016/S0040-4020(02)00829-3

Tetrahedron 58 (2002) 7485–7489
Reactivity of naphthol towards nucleophiles in anodic oxidation
Hesham R. El-Seedi,a,b Shosuke Yamamuraa and Shigeru Nishiyamaa
,
*
aDepartment of Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan
bDepartment of Chemistry, Faculty of Science, El-Menoufia University, Shebin El-Kom, El-Menoufia, Egypt
Received 22 May 2002; accepted 8 July 2002
Abstract—Reactivity of the anodic oxidation of 4-methoxy-1-naphthol 1 in the presence of nucleophiles has been investigated. The reaction
with electron-rich alkenic nucleophiles such as 1-methoxy-4-propenylbenzene 2 and isosafrole 3 gave a very high yield, whereas the reaction
with dihydropyran 4 and dihydrofuran 5 gave a moderate yield, but with ethyl vinyl ether 6 gave a very low yield of the substituted
dihydronaphthofuran derivatives 7–10 and 12, respectively. Unexpectedly, the glycosyl derivative 11 was preferentially produced rather
than naphthofuran 10 upon using 5 as a nucleophile. In addition, the dimers 15 and 16 were obtained in moderate yield without addition of
nucleophile to 1. The mechanism of the oxidation reactions including the [3þ2] and [5þ2] cycloaddition were discussed. q 2002 Elsevier
Science Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Oxidation of phenol and its congeners has been used for the
synthesis of the corresponding quinones and coupling
products.1 In particular, binaphthol derivatives are of
interest, because of characteristic unit of biologically active
natural products, as well as important chiral-auxiliary for
asymmetric induction.2 While a number of oxidants and
their practical usage3 have been developed to achieve the
oxidation of naphthols, few electrochemical oxidations have
been reported.4,6b The reason might be that considerable
efforts were required to acquire optimized conditions by
controlling such parameters as reaction cell (divided or
undivided), solvent (neutral, acidic or basic conditions),
supporting salts, and so on. Despite of such difficulties,
electrochemical reaction would be an efficient method-
ology, from viewpoints of environmental consideration by
employing clean electric energy to provide target
molecules.
To investigate the detailed profile of the oxidation of
naphthols and compare its reactivity with those of phenol
derivatives, 4-methoxy-1-naphthol 1 was subjected to
anodic oxidation in the presence of alkenic nucleophiles
2–6. As expected, the electrochemically generated cation
was reacted with both styrene-(2,3) and vinyloxy-(4–6)
type nucleophiles to construct naphthofurans. The results
are summarized in Table 1 and Fig. 1.
Optimization of the conditions to obtain quantitative yield
of the cycloadducts 7 and 8 using 1-methoxy-4-(1-
propenyl)benzene 2 and isosafrole 3, was achieved by
employing CH3CN as a solvent at constant current
electrolysis (CCE) (entries 1 and 4). The acidic solvents
e.g. CH3CN–AcOH,6b,c Ac2O,6a or CH3NO2–AcOH6f have
been reported to give high yields of oxidation products in
the case of phenol derivatives. In addition to the
cycloadducts 7 and 8, such solvents as Ac2O or CH3CN/
Ac2O, gave undesired acetate 13 and quinone 14 in
moderate yields (entries 2, 3, 5 and 6).
As part of our ongoing project for the anodic oxidation of
phenol derivatives to generate key synthon towards
complicated naturally occurring molecules,5 this paper
describes the oxidation of 4-methoxy-1-naphthol 1 in the
presence of nucleophiles to study scope and limitation of the
oxidation reaction.6,7
Oxidation of 1 provided two kinds of the oxidized forms (A
and B), depending on electrons and protons abstracted
(Scheme 1). Both active species might be stabilized by the
accompanied phenyl residue, which gave a similar effect to
electron-donating substituents in the case of phenol
derivatives. While A underwent a homogeneous coupling
to give dimers 15 and 16, the cation B reacted with
nucleophiles existed to afford naphthofurans 7–10 and 12,
through the [3þ2] cycloaddition reaction.
Keywords: anodic oxidation; 4-methoxy-1-naphthol; electrochemical
reaction; cycloaddition.
Anodic oxidation of 1 with 4 gave the corresponding
cycloadduct 9 in moderate yields (entries 7 and 8), but still
*
Corresponding author. Tel./fax: þ81-45-566-1717;
e-mail: nisiyama@chem.keio.ac.jp
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00829-3

7486
Table 1. The anodic oxidation of 1 with or without nucleophiles and the corresponding products
Entry Nucleophiles equiv. mol mA (F/mol) mV Solvents (ml)
H. R. El-Seedi et al. / Tetrahedron 58 (2002) 7485–7489
Products (%)
7
8
9
10 11
12
13 14 15 16 17 19 21
1
2
3
2
3
12
12
12
10 (2.2) 300–610 A (25)
10 (2.4) 320–690 B (25)
10 (2.4) 380–720 C (25)
96
44
28
50
50
68
55
4
5
6
15
15
15
10 (2.2) 250–550 A (30)
10 (2.2) 350–750 B (25)
10 (2.2) 340–780 C (25)
95
48
36
7
8
4
5
5
25
15 (2.6) 150–650 A (25)
10 (2.5) 180–630 A (25)
45a
19b
32
22
17
5
6
9
10
11
10
10
10
5 (2.1) 300–570
15 (2.5) 180–650 A (25)
80–3c 1500
A (25)
A (25)
79
70
2
6
39
17 11
12d
13
6
20
20
10 (2.2) 180–750 A (35)
13 (2.5) 170–760 A (25)
4e
71
65
12f
14d
15d
13 (2.6) 220–600 A (18)
50–3c 1500
52 45
11 22 58
A (15)
a
1 was recovered in 20% yield.
1 was recovered in 31% yield.
Electrolysis was performed under the CPE conditions, whereas CCE conditions were employed for others.
A 0.33 mmol amount of 1 was used against 0.17 mmol for other entries.
1 was recovered in 17% yield.
b
c
d
e
f
1 was recovered in 17% yield. Solvents: A, CH3CN; B, Ac2O; C, CH3CN–Ac2O (1/1).
better than in the case of 4-methoxyphenol,6a which might
be due to the stability effect, as mentioned above. On the
other hand, unexpectedly, the anodic oxidation with 5 under
the same CCE conditions as that of 4, gave the C-glycoside
118 in high yields (entries 9 and 10). The cycloadduct 10
was obtained under constant potential electrolysis (CPE)
conditions (1500 mV vs. SCE, entry 11). A possible
mechanism is that the acidity in the reaction generated the
O-tetrahydrofuranylation of 1 to give 18, followed by the
O!C glycosyl migration (20) and the additional two-
electron oxidation provided 11 (Scheme 2). Alternatively,
the bicyclo[3.2.1]-type derivative C might be produced by
the cationic [5þ2] cycloaddition of the dienophile 5, and the
abstraction of the methyl group afforded the glycosyl
product 11. The CPE condition (1500 mV vs. SCE) in entry
11 might effect a quick generation of the cation B, leading to
10, before the O-glycosylation of a phenol group, although a
certain amount of 5 would be oxidized (the first oxidation
potential: 1400 mV). To ascertain the O!C migration, 18
was submitted to the same oxidation reaction, which gave
only a trace amount of 11 among the naphthoquinone 14
(58%) and the two dimmers, 15 (31%) and 16 (4%). Upon
reaction of 1 with 5 in the presence of catalytic TsOH, a
mixture of 18 (70%) and 20 (28%) was obtained after 14 h,
while 18 was quantitatively produced after 1 h, which was a
similar reaction time to that of electrolysis. In addition, upon
monitoring the reaction of entry 9 every 10 min, 18 was not
detected, but probably the migration and following
oxidation were so fast as to observe neither 18 nor 20.
Although the O!C migration process might be plausible,
the [5þ2]-type process could not be excluded to explain the
relatively high yield production of 11 within a short period.
The efficient O!C glycosyl migration under Lewis acid
conditions has been reported,9 and the anodic oxidation
provided an alternative methodology employing mild and
safe conditions. In contrast to dihydrofuran 5, its
6-membered derivative 4 gave preferably the cycloadduct
9, and the corresponding C-glycoside 19 was isolated only
in 6% yield under low current conditions (entry 8).10 Further
attempts of explanation of this reactivity difference are
under way.
Anodic oxidation of 1 with ethyl vinyl ether 6 gave the
naphthofuran derivative 12 in low yield, which could be
improved slightly using a high electric current (entries 12
and 13). The undesired acetal 21 in considerable amount
could not be avoided. This is due to the acid-sensitive
character of 6, which reacted with the phenol group of 1
faster than the cycloaddition to the cation, leading to acetal
21.
In entries 8, 10 and 11, the dimers 15 and 16 were obtained
through radical coupling of the one-electron oxidation
product (A in Scheme 1) to give 15, followed by the further
oxidation to give 16. On the other hand, chemical oxidation
of naphthols usually produced benzoquinones (type 14) or
its dimer (type 16), while binaphthol 15 was characteristi-
cally obtained under anodic oxidation conditions.11 As
shown in entries 14 and 15, the anodic oxidation without
nucleophiles in concentrated solution provide the dimer 15
in moderate yield as well as 16.3h While oxidative couplings
by employing oxidants were known,12 electrochemical
conversion of 4-methoxyphenol into the corresponding
biaryl was not accomplished, except the case of 2,3,5-
tribromo-4-methoxyphenol.13
In conclusion, the anodic oxidation of 4-methoxy-1-
naphthol 1 was undertaken to understand their scope and
limitation as substrates in phenolic oxidations. The cation B,
electrolytically generated, reacted with nucleophiles (2–6)
presented to give the corresponding naphthofuran
derivatives (7–10 and 12). Unexpectedly, upon using 5,

H. R. El-Seedi et al. / Tetrahedron 58 (2002) 7485–7489
7487
Figure 1.
Scheme 1.
Scheme 2.

7488
H. R. El-Seedi et al. / Tetrahedron 58 (2002) 7485–7489
the C-glycoside 11 was characteristically obtained which
might adapt an entirely different mechanism. The dimers 15
and 16 were effectively produced by the appropriate
oxidation conditions. In particular, binaphthol 15 was
characteristically produced, different from usual chemical
oxidation. Further electrochemical investigation of other
naphthols14 for a possibility to construct synthetic inter-
mediates of naturally occurring complicated molecules, are
extensively in progress in our laboratory.
J¼8 Hz), 6.90 (1H, dd, J¼2, 8 Hz), 6.94 (1H, d, J¼2 Hz),
7.43 (2H, complex), 7.91 (1H, dd, J¼1.5, 7.2 Hz), and 8.17
(1H, dd, J¼1.5, 7.2 Hz); 13C NMR: d 18.8, 47.1, 55.6, 92.2,
99.7, 100.7, 106.3, 107.8, 119.3, 120.7, 121.1, 122.3, 122.7,
124.7, 125.3, 125.7, 135.1, 147.2, 147.5, 147.7, and 150.1.
EI-MS m/z 334 (45), 301 (21), 278 (19), 231 (16), 212 (41),
189 (32), 149 (42), 122 (100). Found: m/z 334.1218. Calcd
for C21H18O4: M, 334.1204.
3.1.3. 3,4,4a,11a-Tetrahydro-6-methoxynaphtho[20,10:
4,5]furo[2,3-b]-2H-pyran 9. IR (film) 3062, 2930, 1594,
1
and 1459 cm21; H NMR: d 1.56 (1H, m), 1.65 (1H, m),
3. Experimental
1.91 (1H, m), 2.12 (1H, m), 3.49 (1H, dt, J¼1.5, 6.4 Hz),
3.78 (2H, complex), 3.98 (3H, s), 6.11 (1H, d, J¼6.8 Hz),
6.68 (1H, s), 7.47 (2H, dq, J¼1.5, 6.8 Hz), 7.96 (1H, d,
J¼8 Hz), and 8.20 (1H, d, J¼8 Hz); 13C NMR: d 19.9, 22.5,
40.1, 56.1, 60.5, 100.2, 104.5, 120.8, 121.2, 121.3, 122.4,
125.1, 125.4, 126.1, 147.2, and 150.4. EI-MS m/z 256 (100),
241 (18), 225 (22), 211 (13), 185 (11), 128 (11), and 83 (21).
Found: m/z 242.0931. Calcd for C15H14O3: (M2CH2),
242.0941.
IR spectra were recorded on a JASCO Model A-202
1
spectrophotometer. H NMR and 13C NMR spectra were
obtained on a JEOL JNM EX-270, a JEOL JNM GX-400
NMR, or a JEOL JNM ALPHA-400 spectrometer in a
deuteriochloroform (CDCl3) solution using tetramethyl-
silane as an internal standard, unless otherwise stated. Low-
and high-resolution mass spectra were obtained on a Hitachi
M-80 B GC–MS spectrometer operating at the ionization
energy of 70 eV or JEOL JMS-700 spectrometer. All
melting points were obtained on a Yanaco MP-S3 and are
uncorrected. Preparative and analytical TLC were carried
out on silica-gel plates (Kieselgel 60 F254, E. Merck A. G.,
Germany) using UV light, spraying with 5% phospho-
molybdic acid in ethanol for detection. Katayama silica-gel
(K 070) was used for column chromatography.
3.1.4. 2,3,3a,10a-Tetrahydro-5-methoxyfuro[2,3-b]-
naphtho[2,1-d]furan 10. IR (film) 3070, 2928, 1592, and
1
1456 cm21; H NMR: d 2.18 (1H m), 2.34 (1H, m), 3.65
(1H, m), 3.97 (3H, s), 4.10 (1H, m), 4.13 (1H, m), 6.49 (1H,
d, J¼5.9 Hz), 6.68 (1H, s), 7.47 (2H, ddd, J¼1.5, 4.8,
6.8 Hz), 7.95 (1H, d, J¼8.0 Hz), and 8.20 (1H, d,
J¼8.0 Hz). EI-MS m/z 242 (100), 227 (43), 213 (8), 186
(11), 157 (13), and 115 (17). Found: m/z 242.0973. Calcd for
C15H14O3: M, 242.0943.
3.1. General procedure for anodic oxidation of
4-methoxy-1-naphthol 1
3.1.5. 2-Tetrahydrofuran-2-ylnaphthalene-1,4-dione 11.8
Mp 95–968C; IR (film) 3050, 2924, 1663, 1593, 1562, and
1455 cm21; 1H NMR: d 1.70 (1H, m), 1.98 (2H, complex),
2.52 (1H, m), 3.92 (1H, dq, J¼6.8, 7.3 Hz), 4.04 (1H, dq,
J¼5.9, 7.3 Hz), 4.98 (1H, t, J¼8.3 Hz), 7.01 (1H, s), 7.72
(2H, ddd, J¼2.0, 4.9, 7.3 Hz), and 8.06 (2H, ddd, J¼2.0,
2.4, 4.9 Hz). EI-MS m/z 228 (100), 200 (86), 172 (88), 158
(56), 144 (50), 130 (19), and 102 (37). Found: m/z 228.0814.
Calcd for C14H12O3: M, 228.0786.
A solution of 1 in an appropriate solvent was electrolyzed in
the presence of nBu4NBF4 (180 mg) as supporting salts and
appropriate alkenic nucleophiles such as 1-methoxy-4-
propenylbenzene 2, isosafrole 3, dihydropyran 4, dihydro-
furan 5, and ethyl vinyl ether 6 using a glassy carbon beaker
as an anode and a platinum wire as a cathode, in a divided
cell through glass-filters. Based on CV curves, oxidation
potentials of 1 and the representative nucleophile 5 were
620 and 1400 mV vs. SCE (first peaks in CV), respectively.
The nucleophiles were added to the reaction mixture all at
once, since they would not be oxidized under CCE
conditions. Under Ar atmosphere, the electrolysis was
then performed at the oxidation potentials and current of the
substrates given in Table 1. The reaction mixture was
evaporated and purified by column chromatography and/or
preparative TLC.
3.1.6. 2-Ethoxy-5-methoxy-2,3-dihydronaphtho[1,2-
b]furan 12. IR (film) 3065, 2932, 1590, 1554, and
1
1450 cm21; H NMR: d 1.25 (3H, t, J¼7.5 Hz), 3.18 (1H,
dd, J¼2.2, 16.1 Hz), 3.52 (1H, dd, J¼7.2, 16.1 Hz), 3.72
(1H, dq, J¼6.8, 14 Hz), 3.96 (3H, s), 4.04 (1H, dq, J¼6.8,
14 Hz), 5.91 (1H, dd, J¼2.4, 6.8 Hz), 6.75 (1H, s), 7.46 (2H,
ddd, J¼2.0, 4.9, 7.3 Hz), 7.92 (1H, dd, J¼1.5, 7.3 Hz), 8.18
(1H, dd, J¼1.5, 7.3 Hz). Found: m/z 244.1070. Calcd for
C15H16O3: M, 244.1097.
3.1.1. (2R p,3R p)-2,3-Dihydro-5-methoxy-2-(4-methoxy-
phenyl)-3-methylnaphtho[1,2-b]furan 7. Mp 90–918C;
1
IR and H NMR agreed with Ref. 6b; 13C NMR: d 18.9,
3.1.7. 2-(1-Hydroxy-4-methoxy-(2-naphthyl))-4-meth-
oxy-1-naphthol 15. IR (film) 3273, 1643, 1596, and
47.3, 55.6, 56.3, 92.9, 100.7, 114.4, 121.4, 121.8, 122.9,
124.0, 125.5, 125.9, 126.5, 128.0, 133.9, 148.4, 150.8, and
160.1. EI-MS m/z 320 (37), 216 (7), 212 (43), 189 (33), 149
(42), 122 (100). Found: m/z 320.1183. Calcd for C21H20O3:
M, 320.1158.
1
1454 cm21; H NMR (CDCl3/CD3OD 3:1): d 3.98 (6H,
s), 6.71 (2H, s), 7.57 (4H, m), 8.18 (2H, dd, J¼2.4, 7.3 Hz),
and 8.28 (2H, dd, J¼2.4, 7.3 Hz). EI-MS m/z 346 (30), 314
(10), 299 (13), 224 (32), 167 (37), 149 (100), 104 (16), and
71 (18). Found: m/z 346.1201. Calcd for C22H18O4: M,
346.1204.
3.1.2. 2-(2H-Benzo[d ]1,3-dioxol-5-yl)-(2R p,3R p)-2,3-
dihydro 5-methoxy-3-methylnaphtho[1,2-b ]furan 8. IR
1
(film) 3068, 1639, 1596, and 1488 cm21; H NMR: d 1.47
3.1.8. 4-Methoxy-2-(perhydro-2H-pyran-2-yl)-1-
naphthol 19. IR (film) 3295, 3064, 2943, 1598, 1460, and
(3H, d, J¼6.8 Hz), 3.54 (1H, dq, J¼8, 6.8 Hz), 3.95 (3H, s),
5.19 (1H, d, J¼8 Hz), 5.94 (2H, s), 6.60 (1H, s), 6.77 (1H, d,

H. R. El-Seedi et al. / Tetrahedron 58 (2002) 7485–7489
7489
1
1404 cm21; H NMR: d 1.55 (2H, m), 1.63 (2H, m), 1.80
Synthesis 1990, 1141–1143. (b) Barret, R.; Daudon, M.
Tetrahedron Lett. 1990, 31, 4871–4872. (c) Matsumoto, T.;
Imai, S.; Yamamoto, N. Bull. Chem. Soc. Jpn 1988, 61,
911–919. (d) Bao, J.; Wulff, W. D.; Dominy, J. B.; Fumo,
M. J.; Grant, E. B.; Rob, A. C.; Whitcomb, M. C.; Yeung,
S-M.; Ostrander, R. L.; Rheingold, A. L. J. Am. Chem. Soc.
1996, 118, 3392–3405. (e) Hwang, D-R.; Chen, C-P.; Uang,
B-J. Chem. Commun. 1999, 1207–1208. (f) Doussot, J.; Guy,
A.; Ferroud, C. Tetrahedron Lett. 2000, 41, 2545–2547.
(g) Chu, C-Y.; Hwang, D.-R.; Wang, S.-K.; Uang, B.-J. Chem.
Commun. 2001, 980–981. (h) Tanoue, Y.; Sakata, K.;
Hashimoto, M.; Morishita, S.; Hamada, M.; Kai, N.; Nagai,
T. Tetrahedron 2002, 58, 99–104.
(1H, m), 2.00 (1H, m), 3.62 (1H, m), 3.89 (3H, s), 3.92 (1H,
m), 4.58 (1H, dd, J¼1.8, 7.8 Hz), 6.31 (1H, s), 7.40 (2H,
ddd, J¼2.0, 4.9, 7.3 Hz), 8.06 (1H, dd, J¼1.5, 7.3 Hz), and
8.13 (1H, dd, J¼1.5, 7.3 Hz). EI-MS m/z 258 (90), 225 (10),
211 (13), 187 (26), 167 (58), 149 (100), 129 (18), 105 (19),
and 71 (40). Found: m/z 258.1221. Calcd for C16H18O3: M,
258.1254.
3.2. Synthesis of 18 and 20
A mixture of 1 (29 mg, 0.17 mmol) and 5 (0.2 ml,
2.9 mmol) in the presence of catalytic amounts of TsOH
in THF (20 ml) was stirred for 14 h under Ar atmosphere.
The reaction mixture was evaporated and purified by
column chromatography (CH2Cl2) to yield 18 (29 mg,
70%) and 20 (12 mg, 28%).
4. For instance: (a) El-Mobayed, M.; Ismail, N.; Abo El-Enein,
G.; Abd El-Haleem, E. J. Chem. Soc. Pak. 1986, 8, 305–310.
(b) Kashiwagi, Y.; Ono, H.; Osa, T. Chem. Lett. 1993, 81–84.
5. Yamamura, S.; Nishiyama, S. Synlett 2002, 533–543, Many
references cited therein.
3.2.1. 4-Methoxy-2-tetrahydrofuran-2-yl-1-naphthol 20.
IR (film) 3303, 3073, 2950, 1635, 1599, and 1457 cm21; 1H
NMR: d 2.06 (3H, m), 2.45 (1H, m), 3.90 (3H, s), 4.01 (1H,
m), 4.19 (1H, m), 5.14 (1H, dd, J¼6.4, 6.8 Hz), 6.35 (1H, s),
7.48 (2H, ddd, J¼2.0, 4.9, 7.3 Hz), 8.13 (1H, dd, J¼1.5,
7.3 Hz), and 8.21 (1H, dd, J¼1.5, 7.3 Hz); 13C NMR: d
22.5, 33.8, 55.7, 68.6, 83.0, 102.6, 116.1, 121.3, 121.7,
125.3, 125.4, 125.7, 126.1, 144.1, and 148.3. EI-MS m/z 244
(37), 216 (7), 202 (28), 187 (18), 159 (14), 120 (7), and 85
(100). Found: m/z 244.1053. Calcd for C15H16O3: M,
244.1098.
6. Related anodic oxidations: (a) Shizuri, Y.; Nakamura, K.;
Yamamura, S. J. Chem. Soc. Chem. Commun. 1985, 530–531.
(b) Gates, B. D.; Dalidowicz, P.; Tebben, A.; Wang, S.;
Swenton, J. S. J. Org. Chem. 1992, 57, 2135–2143. (c) Kerns,
M. L.; Conroy, S. M.; Swenton, J. S. Tetrahedron Lett. 1994,
35, 7529–7532. (d) Chiba, K.; Jinno, M.; Kuramoto, R.; Tada,
M. Tetrahedron Lett. 1998, 39, 5527–5530. (e) Chiba, K.;
Arakawa, T.; Tada, M. J. Chem. Soc., Perkin Trans. 1 1998,
2939–2942. (f) Chiba, K.; Fukuda, M.; Kim, S.; Kitano, Y.;
Tada, M. J. Org. Chem. 1999, 64, 7654–7656.
7. Part of this work was published: El-Seedi, H. R.; Yamamura,
S.; Nishiyama, S. Tetrahedron Lett. 2002, 43, 3301–3304.
8. (a) Tanoue, Y.; Terada, A.; Taniguchi, H.; Okuma, T.; Kaai,
H.; Anan, M.; Kakara, Y.; Doi, M.; Morishita, S. Bull. Chem.
Soc. Jpn 1993, 66, 3712–3715. (b) Minisci, F.; Coppa, F.;
Fontana, F.; Zhao, L. Gazz. Chim. Ital. 1993, 123, 613–616.
9. (a) Kometani, T.; Kondo, H.; Fujimori, Y. Synthesis 1988,
1005–1007. (b) Suzuki, K.; Matsumoto, T.; Hosoya, T.
J. Synth. Org. Chem. Jpn 1995, 53, 1045–1054.
Acknowledgments
The authors are very grateful to Japan Society for the
Promotion of Science for fellowship to HRE. The generous
financial support from Tokubetsu Kenkyuin Shorei-hi
(Grant in Aid for Scientific Research P 00168) and from
the Amano Industrial Technology Institute is highly
appreciated. The authors are indebted to Mr T. Ogamino
for his technical assistance.
10. If not reduced in situ, 19 carrying a lower oxidation stage than
that of 11, could not be obtained by the [5þ2] process (Scheme
2). At least, reaction with 6 might involve the O!C process.
11. Similar bisnaphthols were obtained by employing electron
donor–acceptor complexes. See: Okamoto, I.; Doi, H.;
Kotani, E.; Takeya, T. Tetrahedron Lett. 2001, 42,
2987–2989.
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14. From among several naphthol derivatives, only 1 satisfied the
chemistry described in this article.