Reductive-alkylation and aromatic coupling reactions of 1,4-benzoquinone derivatives promoted by ethylaluminum dichloride

Article abstract of DOI:10.1016/S0022-328X(98)00865-1

Reactions of several substituted 1,4-benzoquinones with ethylaluminum dichloride in dichloromethane were studied. It was found that some quinones undergo a new radical aromatic coupling under these conditions, while others undergo a 1,6-reductive O-alkylation.

Full text of DOI:10.1016/S0022-328X(98)00865-1

Journal of Organometallic Chemistry 571 (1998) 1–6
Reductive-alkylation and aromatic coupling reactions of
1,4-benzoquinone derivatives promoted by ethylaluminum dichloride
Vitor F. Ferreira a, Francis J. Schmitz b,*
a Departamento de Qu´ımica Orgaˆnica, Uni6ersidade Federal Fluminense, Nitero´i, Rio de Janeiro, CEP 24020-150, Brazil
b Department of Chemistry and Biochemistry, The Uni6ersity of Oklahoma, Norman, 73019-0370, USA
Received 20 January 1998; received in revised form 7 July 1998
Abstract
Reactions of several substituted 1,4-benzoquinones with ethylaluminum dichloride in dichloromethane were studied. It was
found that some quinones undergo a new radical aromatic coupling under these conditions, while others undergo a 1,6-reductive
O-alkylation. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Quinones; Reduction; Alkylation; Aluminum
1. Introduction
benzoquinone derivatives undergo 1,6-addition upon
reaction with alkylaluminum dichlorides (ether solvent)
producing 4-alkoxyphenol analogs similar to com-
pound 10. However, no alkoxyphenol dimers such as 20
were reported in any of these studies.
Because 4-alkoxyphenols are important starting ma-
terials in many syntheses [8–10] and their preparation is
not straightforward, and because 1 and 8 gave such
different types of products we decided to investigate the
scope of this reaction further. In this paper we present
the results of our investigation of the reductive-alkyla-
tion of variously substituted 1,4-benzoquinones with
ethylaluminum dichloride.
In the course of studies directed to shortening the
synthesis of perfragilin B (1) [1], a metabolite isolated
from the bryozoan Membranipora perfragilis [2,3],
Lewis acid catalyzed Diels-Alder reactions of 2,3-
dichloro-1,4-benzoquinone and 2-aza-1,3-bis-(t-butyldi-
methylsilyloxy)-1,3-butadiene [4] were attempted. When
ethylaluminum dichloride was investigated as the cata-
lyst no Diels-Alder product was obtained, but instead
the alkoxyphenol derivative 10 was obtained in 75–85%
yields (Scheme 1). The same results were obtained when
the azadiene was left out of the reaction. Surprisingly,
reaction of the monochlorobenzoquinone, 2-chloro-1,4-
benzoquinone (8), with ethylaluminum dichloride af-
forded the phenol-dimer 20 in 61% yield (Scheme 1).
A search of the literature revealed that the reaction
of alkylaluminum dichlorides with 1,4-benzoquinones
had been already investigated by Pasynkiwicz [5,6] and
Florjanczyk [7] who found that some chlorinated 1,4-
2. Results
The reactions were carried out between 1,4-benzo-
quinone derivatives and two equivalents of ethylalu-
minum dichloride at −78°C in dichloromethane.
Reactions were quenched by adding methanol at room
temperature and then aqueous HCl (15%). Scheme 1
shows the benzoquinone derivatives 1–9 used in our
investigation and the corresponding products 10–21
which were formed.
* Corresponding author. Tel.: +1 405 3255581; fax: +1 405
3256111; e-mail: fjschmitz@chemdept.chem.ou.edu
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00865-1

2
V.F. Ferreira, F.J. Schmitz / Journal of Organometallic Chemistry 571 (1998) 1–6
Scheme 1. Reactions for the preparation of compounds 10–21.
respectively) while the methylene group (l 3.95) showed
As can be seen in Scheme 1 1,4-benzoquinones 1–4
a crosspeak with C-5 (l 151.6) establishing the vicinal
relationship between the methyl and ethoxy groups.
Correlations were observed in the HMBC spectrum
between H-3/C-1, C-2, C-4, C-5 and H-6/C-1, C-2, C-4,
C-5. These correlations considered together with the
absence of any observable coupling between H-6 and
H-3 and lack of correlations in HMBC spectrum be-
tween H-6/C-3 and H-3/C-6 indicated that the bond
between the aromatic rings occurred at position 2. The
structures of 19 and 20 were assigned by comparison of
their chemical shifts with those of 21, the lack of
observable coupling between the aromatic protons, and
mass spectral data.
It is well known in the literature that benzoquinones
can easily form persistent radical complexes containing
aluminum [11,12] and other metals [13–15]. Pasyn-
kiewicz [5] proved by ESR analysis that the conversion
of I to IV and VI involved a radical intermediate and
proposed a radical mechanism such as that shown in
Scheme 2 (III“IV or III“VI).
In addition to the alkylation of oxygen by ethyl
radicals observed in the present work and by earlier
workers [5–7], the results with monosubstituted 1,4-
benzoquinones 7–9 indicate that coupling between
phenyl radicals also occurs to give dimeric and/or
oligomeric products. The selectivity in orientation in
the coupling observed for 7–9 suggests that the inter-
mediate for coupling may be a mono ethylated radical
such as VII. Dimerization of VII at the unhindered site
afforded the 4-ethoxyphenol derivatives 10–14 in good
yields and no dimeric products were detected. From
benzoquinones 1 and 5, the simple 1,6-reduction prod-
ucts 10a and 15a were also isolated in 22 and 7%,
respectively. The yield of ethoxyphenol 12 was much
higher than that reported by Florjanczyk [5]. This may
be due either to solvent differences or the higher ratio
of EtAlCl2/quinone (2:1 vs 1:1) used. Attempts to use a
lower ratio of EtAlCl2/quinone caused a decrease in the
yield of 12. The methylthio substituted 1,4-benzo-
quinone 5 gave low yields of reduction products and 6
gave no reduction product.
The formation of the 4-alkoxyphenols is not regiose-
lective. No selectivity for O-alkylation was observed
when 2,6-dimethyl-1,4-benzoquinone (4) was reacted;
an equimolar mixture of 13 plus 14 was isolated in 72%
overall yield. Also, no selectivity in the formation of the
4-ethoxyphenols 17/18 was observed when 2-phenyl-
1,4-benzoquinone (7) was reacted.
When the 1,4-benzoquinone derivatives 7–9 were
subjected to this reaction, the main products obtained
were the alkoxyphenyl dimers 19–21, in moderate to
good yields, instead of the usual 4-alkoxyphenols.
The structures of substances 19–21 were determined
by a combination of mass, 1H- and 13C-NMR spec-
troscopy. For 21 (C18H22O4, HR-FAB-MS m/z
302.1510) the HMBC spectrum revealed multiple bond
correlations between the aromatic methyl group (l
2.21) and C-5, C-4 and C-3 (l 151.6, 128.8, 118.9,

V.F. Ferreira, F.J. Schmitz / Journal of Organometallic Chemistry 571 (1998) 1–6
3
Scheme 2. Possible mechanism for the formation of substances 19–21.
we obtained the 4-alkoxy dimer 23 as the major
product, in addition to mono-ether 24, di-ether 25 and
C-alkylated 1,4-naphthoquinone 26 as minor
components.
ortho to the oxygen radical site followed by enolization
(prior to or during work up) would give the observed
products. If the dimerization occurred prior to ethyl
ether formation, the selective ether orientation in the
dimer would be difficult to rationalize. It is not clear
why the monosubstituted 1,4-quinones give dimers as
major products whereas 1,4-benzoquinone itself and
disubstituted 1,4-benzoquinones of various substituted
patterns give predominantly 1,6-addition products.
The reaction of 1,4-naphthoquinone (22) with ethyla-
luminum dichloride has previously been investigated by
Florjanczyk et al. [7] who found that 4-alkoxynaphthol
24 was formed in 26% yield along with 1,4-naphtho-
quinol (44%) (Scheme 3). Using our reaction conditions
3. Conclusion
The present study has shown that when 1,4-benzo-
quinone derivatives 1–9 are treated with two equiva-
lents of EtAlCl2, 4-alkoxyphenols (10–15, 17, 18) or
4-alkoxyphenol dimers (19–21) are formed. To the best
of our knowledge this is the first time that such dimers
have been reported for this kind of reaction.

4
V.F. Ferreira, F.J. Schmitz / Journal of Organometallic Chemistry 571 (1998) 1–6
Scheme 3. Reaction of 1,4-naphthoquinone (22) with EtAlCl2 in CH2Cl2.
4. Experimental
ml of 15% HCl (to pH ꢀ6) were slowly added sequen-
tially. The resulting gelatinous mixture was extracted
with dichloromethane (3×15 ml). The resulting cloudy,
organic phase was filtered through a celite column,
dried over anhydrous sodium sulfate, and concentrated
under reduced pressure. The residues were chro-
matographed on silica gel columns or preparative TLC
plates and eluted with a mixture of hexane:ethyl acetate
(9:1).
All solvents were redistilled. Dichloromethane was
freshly distilled from calcium hydride. High resolution
fast atom bombardment mass spectra (HRFABMS)
were recorded in the positive ion mode on a VG ZAB-E
mass spectrometer using 3-NBA matrix. Low resolution
electron-impact mass spectra (12 eV) were measured on
a Hewlett-Packard 5985 instrument. NMR experiments
were performed on Varian XL-300, VXR-400 and
VXR-500 (3 mm 1H/13C switchable gradient mi-
croprobe MDG-500-3) instruments; signals are reported
in parts per million (ppm) referenced to the solvent
used. All NMR pulse sequences were run using stan-
dard Varian software version 4.3 (HMBC, nJCH=9
Hz). IR spectra were recorded on a Bio-Rad 3240-SPC
FT spectrophotometer. Freshly purified samples were
used for measurement of physical constants and spec-
tral data. The reaction mixtures were separated using
preparative TLC rotors coated with silica gel in a
Chromatotron model 7924 (Harrison Research Co.).
Benzoquinones 2, 4, 7, 8 and 9 were purchased from
Aldrich. 2,3-Dichloro-1,4-benzoquinone (1) was pre-
pared by the method of Norris [16] as modified by our
group [17]. In this reaction benzoquinone 3 is a by
product. Methylthiobenzoquinones 5 and 6 were pre-
pared by the method of Wladislaw [18].
4.2. 2,3-Dichloro-4-ethoxyphenol (10) and
2,3-diclorohydroquinone (10a)
Obtained in 75–85% yield from 2,3-dichlorobenzo-
quinone (1, 75 mg, 0.42 mmol); m.p. 74–75°C; IR
1
(film) (wmax 3370 (bs), 2987 (m), 1596 cm−1; H-NMR
(CDCl3) l 1.42 (t, 3H, J=7 Hz, CH3), 4.04 (q, 2H,
J=7 Hz, CH2), 5.33 (s, 1H, OH), 6.80 (d, 1H, J=8.8
Hz), 6.89 (d, 1H, J=8.8 Hz); 13C-NMR (CDCl3) l 14.8
(CH3), 65.9 (CH2), 113.4 (CH/C-5 or C-6), 113.5 (CH/
C-5 or C-6), 119.9 (C-2 or C-3), 122.1 (C-2 or C-3),
146.4 (C-1), 149.4 (C-4); LRMS (12 eV) m/z (relative
intensity) 206 (56), 182 (10), 180 (48), 178 (100); HR-
FABMS m/z 205.9871 [M+1]+ (C8H8O2Cl2, 3.0
mmu). 2,3-Dichloro-hydroquinone (10a) was also ob-
tained in 22% yield; m.p. 146–147°C; 1H-NMR
(CDCl3) l 5.24 (s, 1H, OH), 6.89 (s, 1H); LRMS (12
eV) m/z (relative intensity) 182 (10), 180 (65), 178 (100),
142 (14) 114 (9); HRFABMS m/z 177.9557 (M+)
(C6H4O2Cl2, 3.1 mmu).
4.1. General procedure
To a solution of the appropriate benzoquinone
derivative (1 mmol) in 5 ml of dry dichloromethane, 2
ml (two equivalents) of a solution of 1 M EtAlCl2 in
hexane was added dropwise under a nitrogen atmo-
sphere over a period of 30 min at −78°C. The solution
turned deep blue and was stirred at this temperature for
1 h and then for 2 h at room temperature. To this
mixture, 2 ml of methanol, 10 ml of water and then 5
4.3. 4-Ethoxyphenol (11)
Obtained in 77% yield from 1,4-benzoquinone (2, 120
mg, 1.10 mmol); m.p. 65–66 (lit. 65–67°C) ; H-NMR
(CDCl3) l 1.37 (t, 3H, J=7 Hz, CH3), 3.96 (q, 2H, J=7
Hz, CH2), 5.33 (s, 1H, OH), 6.77 (d, 1H, J=9 Hz), 6.78
(d, 1H, J=9 Hz); 13C-NMR (CDCl3) l 14.8 (CH3),
1

V.F. Ferreira, F.J. Schmitz / Journal of Organometallic Chemistry 571 (1998) 1–6
5
64.3 (CH2), 115.7 (CH), 116.1 (CH), 119.9 (C), 149.4
(C), 152.7 (C); LRMS (12 eV) m/z (relative intensity)
138 (100), 110 (47).
Hz, 1H), 7.36–7.41 (m, 1H, Ph), 7.46–7.48 (m, 4H,
Ph); 13C-NMR (CDCl3) l 14.9 (Me), 64.0 (CH2), 115.2
(CH, C-5 or C-6), 115.9 (C-5 or C-6), 116.4 (CH, C-2),
128.0 (Ph), 128.5 (C-3), 128.9 (Ph), 129.1 (Ph), 146.2
(C-1), 152.8 (C-4); LRMS (12 eV) m/z (relative inten-
sity) 214 (100), 186 (32); HRFABMS m/z 214.0995
(M+) (C14H14O2, −0.1 mmu).
4.4. 2,5-Dichloro-4-ethoxyphenol (12)
Obtained in 80% yield from 2,5-dichlorobenzo-
quinone (3, 120 mg, 0.68 mmol); m.p. 58–58°C; IR
(film) (wmax 3408 (bs), 1465 (s), 1201 (s) cm−1; 1H-NMR
(CDCl3) l 1.42 (t, 3H, J=7 Hz, CH3), 4.00 (q, 2H,
J=7 Hz, CH2), 5.19 (s, 1H, OH), 6.87 (s, 1H), 7.05 (s,
1H); 13C-NMR (CDCl3) l 14.6 (CH3), 65.7 (CH2),
114.3 (CH/C-3 or C-6), 117.6 (CH/C-6 or C-6), 117.7
(C-2 or C-5), 122.7 (C-2 or C-5), 145.4 (C-1), 148.6
(C-4); LRMS (12 eV) m/z (relative intensity) 206 (M+,
100), 208 [(M+2)+, 62], 210 [(M+4)+, 11], 182 (11),
180 (59), 178 (95); HRFABMS m/z 205.9918 (M+)
(C8H8O2Cl2, −1.7 mmu).
4.8. 4-Ethoxy-2-phenylphenol (18)
Obtained in 7.5% yield. Oil, IR (film) (wmax 3413 (bs)
cm−1; 1H-NMR (CDCl3) l 1.28 (t, 3H, J=7 Hz, CH3),
3.92 (q, 2H, J=7 Hz, CH2), 4.71 (s, 1H, OH), 6.74 (d,
J=9 Hz, 1H, H-5), 6.83 (d, J=3 Hz, 1H, H-3), 6.86
(d, J=9 Hz, 1H, H-6), 7.36–7.41 (m, 1H, Ph), 7.46–
7.48 (m, 4H, Ph); 13C-NMR (CDCl3) l 14.8 (Me), 65.2
(CH2), 114.2 (CH, C-5 or C-6), 115.1 (C-5 or C-6),
117.6 (CH, C-3), 127.0 (Ph), 127.8 (Ph), 129.3 (Ph),
132.2 (C-2), 138.1 (Ph), 149.5 (C-1), 149.9 (C-4); LR-
FABMS m/z (relative intensity) 214 (100), 186 (14);
HRFABMS m/z 214,0996 (M+) (C14H14O2, −0.2
mmu)
4.5. 4-Ethoxy-2,6-dimethylphenol (13) and 4-ethoxy-3,
5-dimethylphenol (14)
Obtained as a mixture (1:1) in 72% yield from 2,6-
dimethy-1,4-benzoquinone (4, 136 mg, 1 mmol). 1H-
NMR (CDCl3) l 1.36 and 1.38 (t, J=7 Hz, Me), 2.10
and 2.15 (s, Me), 3.7 and 3.94 (q, J=7 Hz, CH2), 6.46
(s, 1H, CHolefin), 6.54 (s, 1H, CHolefin).
4.9. 5,5%-Diethoxy-2,2%-dihydroxy-4,4%-diphenylbiphenyl
(19)
1
Obtained in 40% yield, m.p. 194–195°C; H-NMR
(CDCl3) l 1.31 (t, J=7 Hz, 3H, Me), 3.97 (q, J=7 Hz,
2H, OCH2), 5.75 (bs, 1H, OH), 6.94 (s, 1H, H-6), 7.04
(s, H-3), 7.34 (t, 1H, J=7 Hz, p-Ph), 7.41 (t, 2H, J=7
Hz, m-Ph), 7.59 (t, 2H, J=7 Hz, o-Ph); 13C-NMR
(CDCl3) l 14.8 (Me), 65.2 (CH2), 116.1 (C-6), 119.2
(C-3), 123.5 (C-1), 127.1 (Ph), 127.9 (Ph and C-4), 129.3
(Ph), 132.5 (Ph), 146.6 (C-2), 151.1 (C-5); LRMS (12
eV) m/z (relative intensity) 426 (M+, 100), 427 [(M+
H)+, 15]; HRFABMS m/z 426.1833 (M+) (C28H26O4,
−0.2 mmu).
4.6. 4-Ethoxy-2,5-di-(methylthio)phenol (15) and 2,5-
di-(methylthio)hydroquinone (15a)
Obtained in 10% yield from 2,5-(methyl-
thio)benzoquinone (5, 120 mg, 0.60 mmol); m.p. 73–
1
74°C; IR (film) (wmax 3400 cm−1; H-NMR (CDCl3) l
1.42 (t, 3H, J=7 Hz, CH3), 2.29 (s, 3H, SMe), 2.39 (s,
3H, SMe), 4.02 (q, 2H, J=7 Hz, CH2), 6.32 (s, 1H,
OH), 6.74 (s, 1H), 6.92 (s, 1H); 13C-NMR (CDCl3) 14.1
(SMe), 14.7 (SMe), 20.2 (Me), 65.2 (CH2), 110.9 (CH/
C-3 or C-6), 115.3 (C-2 or C-5), 148.9 (C-1), 151.1
(C-4); LRMS (12 eV) m/z (relative intensity) 230 (100),
202 (98), 201 (13); HRFABMS m/z 230.0437 (M+)
4.10. 5,5%-Diethoxy-2,2%-dihydroxy-4,4%-dichlorobiphenyl
(20)
Obtained in 61% yield from 2-chlorobenzoquinone
(C10H14O2S2,
−0.2
mmu).
2,5-Di-(methylthio)-
(8, 120 mg, 0.68 mmol); m.p. 170–171°C; IR (film)
1
(wmax 3401 (bs) cm−1, H-NMR (CDCl3) l 1.46 (t, 3H,
hydroquinone (15a) was also obtained in 7% yield; m.p.
127–129°C); IR (film) (wmax 3408 (bs), 1201 (s) cm−1
;
J=7 Hz, CH3), 4.04 (q, 2H, J=7 Hz, CH2), 5.31 (s,
1H, OH), 6.79 (s, 1H, H-6), 7.08 (s, 1H, H-3); 13C-
NMR (CDCl3) l 14.7 (CH3), 65.8 (CH2), 116.3 (C-6),
118.8 (C-3), 122.6 (C-1), 124.3 (C-4), 146.5 (C-2), 149.2
(C-5); LRMS (12 eV) m/z (relative intensity) 342 (M+,
100), 344 (65), 346 (6), 314 (10), 286 (37); HRFABMS
m/z 342.0438 (M+) (C16H16O4Cl2, −1.2 mmu).
1H-NMR (CDCl3) l 2.34 (s, SMe), 6.05 (bs, OH), 7.05
(s, CH); LRMS (12 eV) m/z (relative intensity) 202
(M+, 100), 187 (19); HRFABMS m/z 202.0119 (M+)
(C8H10O2S2, 0.3 mmu).
4.7. 4-Ethoxy-3-phenylphenol (17)
Obtained in 10% yield from 2-phenylbenzoquinone
4.11. 5,5%-Diethoxy-2,2%-dihydroxy-4,4%-dimethylbi-
phenyl (21)
(7, 184 mg, 1 mmol); oil, IR (film) (wmax 3420 cm−1
;
1H-NMR (CDCl3) l 1.39 (t, 3H, J=7 Hz, CH3), 4.00
(q, 2H, J=7 Hz, CH2), 4.89 (s, 1H, OH), 6.80 (bs, 1H,
H-2), 6.81 (dd, J=3 and 9 Hz, 1H, H-6), 6.89 (d, J=9
Obtained in 79% yield from 2-methylbenzoquinone
(9, 122 mg, 1 mmol); m.p. 168–169°C; IR (film)

6
V.F. Ferreira, F.J. Schmitz / Journal of Organometallic Chemistry 571 (1998) 1–6
(wmax 3441 cm−1; 1H-NMR (CDCl3) l 1.38 (t, J=7 Hz,
3H, Me), 2.21 (s, Me), 3.96 (q, J=7 Hz, 2H, OCH2),
6.69 (s, H-6), 6.79 (s, H-3); 13C-NMR (CDCl3) l 14.9
4.15. 2-Ethyl-1,4-naphthoquinone (26)
Obtained in 4% yield; oil, IR (film) (wmax 1663 (bs)
cm−1; 1H-NMR (CDCl3) l 1.23 (t, 3H, J=7 Hz, CH3),
2.61 (q, 2H, J=7 Hz, CH2), 6.78 (bs, 1H, H-3), 7.70–
7.73 (m, 2H, H-6 and H-7), 8.05–8.11 (m, 2H, H-5 and
H-8); LRFABMS m/z (relative intensity) 187 [(M+
1)+, 17].
(CH2C6 H3), 16.0 (Me), 64.4 (CH2), 113.8 (C-6), 118.9
(C-3), 121.3 (C-1), 128.8 (C-4), 146.0 (C-2), 151.6 (C-5);
HMQC 2.20/16.0, 3.95/64.4, 6.69/113.8, 6.79/118.9;
HMBC (nJCH=9 Hz) 1.38 (Me)/64.4, 2.21 (Me)/151.6,
128.8, 118.9, 3.95 (CH2)/151.6, 14.9, 6.69 (CH)/151.6,
145.9, 128.8, 121.3, 6.79 (CH)/151.6, 145.9, 121.3;
LRMS (12 eV) m/z (relative intensity) 302 (M+, 100);
HRFABMS m/z 302.1510 (M+) (C18H22O4, 0.8 mmu).
Acknowledgements
Fellowship from CAPES (Brazil) to V.F.F. is grate-
fully acknowledged. This work was supported in part
by Department of Commerce, NOAA Sea Grant Pro-
ject NA66RGO172.
4.12. 4,4%-Diethoxy-1,1%-dihydroxy-2,2%-binaphthyl (23)
Obtained in 35% yield from 1,4-naphthoquinone (158
mg, 1 mmol); m.p. 190–191°C; IR (film) (wmax 3422 (bs)
1
cm−1; H-NMR (CDCl3) l 1.53 (t, J=7 Hz, 3H, Me),
4.17 (bs, 2H, OCH2), 5.39 (bs, 1H, OH), 6.72 (s, 1H,
H-3), 7.59 (bs, 2H, H-5 and H-8), 8.29 (bs, 2H, H-6 and
H-7); 13C-NMR (CDCl3) l 14.8 (Me), 64.1 (CH2),
106.1, 115.0, 122.0 (C–H), 122.2 (C–H), 125.9, 126.2
(C–H), 126.5 (2xC–H), 142.4 (C-1), 149.4 (C-4);
LRMS (12 eV) m/z (relative intensity) 374 (M+, 100),
328 (11), 299 (21), 216 (82), 186 (93), 172 (69); HR-
FABMS m/z 374.1545 (M+) (C24H22O4, −2.7 mmu).
References
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It was obtained in 9% yield; oil, IR (film) (wmax 3411
1
(sb), 1625 (s), 1595 (s) cm−1; H-NMR (CDCl3) l 1.53
(t, 3H, J=7 Hz, CH3), 4.13 (q, 2H, J=7 Hz, CH2),
5.10 (bs, 1H, OH), 6.62 (d, J=8 Hz, 1H, H-2), 6.70 (d,
J=8 Hz, 1H, H-3) 7.40–7.50 (m, 2H, H-6 and H-7),
8.10 (m, 1H, H-5 or H-8), 8.26 (m, 1H, H-5 or H-8).
[12] A. Hudson, J. Organomet. Chem. 194 (1980) 137.
[13] C. Blomberg, H.H. Grootveld, T.H. Gerner, F. Bickelhaupt, J.
Organomet. Chem. 24 (1970) 549.
4.14. 1,4-Diethoxynaphthalene (25)
Obtained in 3% yield; oil, IR (film) (wmax 1595 (s),
[14] H. Joela, S. Kasa, R. Ma¨kela¨, E. Sato, K. Hannomen, Magn.
Reson. Chem. 28 (1990) 261.
[15] T.L. Sima´ndi, A. Rockenbauer, Ero. Polym. J. 27 (1991) 523.
[16] R.K. Norris, S. Sternhell, Aust. J. Chem. 26 (1973) 333.
[17] V.F. Ferreira, F.J. Schmitz, Org. Prep. Proced. Int. 30 (1998)
115.
1
1273 (s) cm−1; H-NMR (CDCl3) l 1.51 (t, 6H, J=7
Hz, CH3), 4.14 (q, 4H, J=7 Hz, CH2), 6.68 (s, 2H, H-2
and H-3), 7.47–7.50 (m, 2H, H-6 and H-7), 8.20–8.24
(m, 2H, H-5 and H-8); LRFABMS m/z (relative inten-
sity) 216 (100), 187 (24), 174 (10), 159 (26).
[18] B. Wladislaw, L. Marzorati, C. Di Vita, Synthesis (1983) 464.
.