Studies on the chemistry of 2-(2-oxo-3-phenylpropyl)-benzaldehydes: Novel total synthesis of 3-phenylnaphthalen-2-ols and 2-hydroxy-3-phenyl-1,4- naphthoquinones

Article abstract of DOI:10.1016/j.tet.2004.10.043

We describe the first studies on the chemistry of 2-(2-oxo-3-phenylpropyl) benzaldehydes, which were converted into 3-benzylisochromen-1-ones via the corresponding 2-(2-oxo-3-phenylpropyl)benzoic acid. The 2-(2-oxo-3-phenylpropyl) benzaldehydes proved to be convenient starting materials for the synthesis of 3-phenyl-2-naphthols. Oxidation of the latter compounds resulted in a novel, efficient synthesis of 3-phenyl-1,2-naphthoquinones, which were efficiently transformed into 2-hydroxy-3-phenyl-1,4-naphthoquinones.

Full text of DOI:10.1016/j.tet.2004.10.043

Tetrahedron 61 (2005) 485–492
Studies on the chemistry of
2-(2-oxo-3-phenylpropyl)-benzaldehydes:
novel total synthesis of 3-phenylnaphthalen-2-ols and
2-hydroxy-3-phenyl-1,4-naphthoquinones
*
Ana Martınez, Marcos Fernandez, Juan C. Estevez, Ramon J. Estevez and Luis Castedo
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Departamento de Quımica Organica and Unidade Asociada (C.S.I.C.), Universidade de Santiago, 15782 Santiago de Compostela, Spain
Received 10 September 2003; revised 11 October 2004; accepted 14 October 2004
Abstract—We describe the first studies on the chemistry of 2-(2-oxo-3-phenylpropyl)benzaldehydes, which were converted into 3-
benzylisochromen-1-ones via the corresponding 2-(2-oxo-3-phenylpropyl)benzoic acid. The 2-(2-oxo-3-phenylpropyl)benzaldehydes
proved to be convenient starting materials for the synthesis of 3-phenyl-2-naphthols. Oxidation of the latter compounds resulted in a novel,
efficient synthesis of 3-phenyl-1,2-naphthoquinones, which were efficiently transformed into 2-hydroxy-3-phenyl-1,4-naphthoquinones.
q 2004 Elsevier Ltd. All rights reserved.
Molecules with the quinoid structure constitute one of the
most interesting classes of compounds in organic chemistry.
Their syntheses as well as their diverse chemical and
physical properties have been compiled into two volumes of
Patai’s series ‘The Chemistry of Functional Groups’.1 The
perennial chemical interest in naphthoquinones is due to
their biological properties, their industrial applications and
their potential as intermediates in the synthesis of
heterocycles.2
quinones consists of the oxidation of 2-naphthols,6g,7 which
are difficult to access, or the more problematic oxidation of
the more readily available 1-naphthols.8 Both approaches
have been efficiently used in the synthesis of complex
o-naphthoquinones.9 Moreover, oxidation of simple
o-naphthoquinones is a common method for the preparation
of 2-hydroxy-1,4-naphthoquinones.10 By contrast, similar
chemistry for 3-phenyl-1,2-naphthoquinones 15 (Scheme 2)
is very limited and, although some methods have been
described for the preparation of such targets from 3-phenyl-
1-naphthols,11 to the best of our knowledge the preparation
of quinones 15 from 3-phenyl-2-naphthols 14 (Scheme 2)
has not been described.12 On the other hand, only one
example has been reported involving the oxidation of
3-phenyl-1,2-naphthoquinones 15 to 3-phenyl-2-hydroxy-
1,4-naphthoquinones 2 (Scheme 1).12a
Although a large number of 1,2-naphthoquinones have been
described, 1,4-naphthoquinones are more abundant—par-
ticularly those that have one hydroxy group attached
directly to the quinone moiety, a wide variety of which
are found in nature. Most of these compounds exhibit
interesting biological activity and this is reflected in the ever
increasing number of publications concerning their iso-
lation, characterization and synthesis in the laboratory.3
Natural hydroxyquinones vary in structural complexity
from the simple hydroxynaphthoquinones such as lawsone,
the main component of a natural dye,4 to hydroxyphenyl-
naphthoquinones5 or complex structures such as the trimeric
hydroxynaphthoquinone conocurvone, a potential anti-HIV
agent.6
This paper represents a novel contribution to the chemistry
of 3-phenyl-2-hydroxynaphthoquinones 2 and includes the
first general method for the synthesis of 3-phenyl-2-
naphthols 14. A novel oxidation is described for the con-
version of compounds 14 to the corresponding o-naphtho-
quinones 15, which were further oxidized to 3-phenyl-2-
hydroxy-1,4-naphthoquinones 2.
The starting point for this work was the observation that a
2-phenyl-1,4-naphthoquinone subunit is present in the
polycyclic ring system of a wide range of quinonoid
compounds, including benzofuronaphthoquinones 4,13
benzopyronaphthoquinones 514 and indolonaphthoquinones
The common method for the synthesis of simple o-naphtho-
Keywords: Quinones; Cyclization; Oxidation; Aldol reaction.
* Corresponding author. Tel.: C34 981 563100x14242; fax: C34 981
591014; e-mail: qorjec@usc.es
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.10.043

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486
Scheme 1.
615 (Scheme 1). This structural relationship was the basis for
the development of a practical synthesis of these naphtho-
quinone targets from 2-hydroxy-3-phenyl-1,4-naphtho-
quinones (2), which were in turn prepared by attachment
of a phenyl substituent to the C3 position of 2-hydroxy-1,4-
naphthoquinones and/or, more directly and efficiently, by
mixed Claisen condensation of alkyl o-phenylethylphenyl-
acetates 1. However, this interesting methodology has
not yet been fully exploited, probably due to the limited
scope in terms of the availability of the necessary starting
materials.
2-Benzylidene-1-indanone 8a,17 formed by the aldol
condensation of 1-indanone 7a and benzaldehyde, was
subjected to controlled catalytic hydrogenation. The only
process observed was the desired selective reduction of the
double bond and this gave a quantitative yield of the
previously obtained benzylindanone 9a.18 The IR spectrum
of 9a showed a band at 1708 cmK1 corresponding to the
carbonyl group. The 1H NMR spectrum included four
doublet of doublets at 2.67, 2.86, 3.17 and 3.42 ppm, which
are due to the two methylene groups, together with a
multiplet at 3.01 ppm due to the proton in the a-position to
the carbonyl. Subsequent treatment of compound 9a with
NaBH4 in methanol led to complete transformation of this
compound into a mixture of 2-benzyl-1-indanols,19 which
was heated under reflux with concentrated sulfuric acid in
order to promote its dehydration.20 The expected 2-benzyl-
indene 10a was obtained in 93% yield. The 1H NMR
spectrum of 10a contained signals between 7.12 and
7.40 ppm for a total of nine aromatic protons, a singlet at
6.57 ppm corresponding to the proton of the double bond,
and two singlets at 3.33 and 3.86 ppm, each due to two
protons, which were assigned to the two methylene groups.
The next step involved cleavage of the double bond in
In the search for new routes for the preparation of 3-phenyl-
2-hydroxy-1,4-naphthoquinones 2 without the above
limitations, we reasoned that alkyl 3-phenyl-2-ketopropyl
benzoates 3 should undergo a mixed Claisen condensation
in a similar way to ketoacid esters 1 to give the
naphthoquinones 2 on the basis that compounds 3 also
have the necessary carbon skeleton and functionality for
this transformation (Scheme 1). In order to confirm this
hypothesis, we decided to explore the preparation of the
practically unknown ketoacids 3 by the novel route outlined
in Scheme 2, starting from 1-indanones.16
Scheme 2. 2, 7, 8, 9, 10, 11, 14, 15: (a) RZH; (b) RZOMe. Conditions. (i) NaMeO/MeOH, rt, 15–27 h. (ii) H2, Pd/C, AcOEt, 1 atm, 1.5–3.5 h. (iii) (a) NaBH4,
MeOH, rt, 1–1.5 h; (b) H2SO4, reflux, 1–2 h. (iv) (a) O3, K78 8C, 3–6 min; (b) Me2S, K78 8C (4–7 h), rt (13 h). (v) CrO3, H2SO4, H2O, rt, 45 min. (vi) H2SO4,
MeOH, reflux, 75 min. (vii) NaMeO, MeOH, reflux, 3 h. (viii) NaOH aq, rt, 1.5–2 h. (ix) Fremy’s salt, K2HPO4, acetone, rt, 1–4 h. (x) H2SO4, MeOH, reflux,
29 h.

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487
indene 10a, which was achieved by ozonolysis in dichloro-
methane at K78 8C, and subsequent reduction of the
resulting ozonide with methylene sulfide.21 In this way,
ketoaldehyde 11a was obtained in 71% yield and was easily
identified from its analytical and spectroscopic data. The 1H
NMR spectrum showed a singlet at 9.98 ppm—correspond-
ing to the aldehyde proton—and the 13C NMR spectrum
contained signals at 193.5 and 204.9 ppm corresponding to
ketone and aldehyde carbonyls, respectively. Finally,
oxidation of this ketoaldehyde under Jones conditions22
(CrO3, H2O, H2SO4) led to a mixture of compounds. The
major component (82% yield) was the expected ketoacid
12a,23 which showed in its IR spectrum an OH band at
2931–2856 cmK1 and carbonyl bands at 1714 and
1693 cmK1 corresponding to the carboxyl and the ketone
17 into naphthol 18, a possible precursor of naphthoquinone
2a, would involve a mixed Claisen cyclization followed
by aromatization of ring B. Formation of 13 as the only
reaction product can be explained by assuming that enolate
16 is kinetically and thermodynamically more favoured than
enolate 17, due to interaction of the enolate moiety with the
methoxycarbonyl group.
Although our initial route to prepare hydroxyphenyl-
naphthoquinone 2a from ketoacid ester 12b failed, satis-
factory results were obtained on using its precursor,
ketoaldehyde 11a. Thus, when 11a was subjected to basic
conditions, a quantitative yield of 2-naphthol 14a was
obtained as a result of an intramolecular aldol condensation
(Scheme 2). The IR spectrum of the product contained a
functionalities, respectively. The H NMR and 13C NMR
typical band for a phenolic hydroxy group at 3457 cmK1
;
1
1
spectra of 12a were very similar to those of the precursor
11a, with the 13C spectrum containing signals at 168.4 and
205 ppm due to the carboxyl and ketone carbonyls,
respectively. The minor compound, isolated in 18% yield,
was identified as lactone 1323 on the basis of its spectro-
scopic properties. For example, the IR spectrum contained a
lactone carbonyl band at 1727 cmK1 and the 1H NMR
showed a singlet at 6.16 ppm due to the proton of the double
bond and another singlet at 3.85 due to the methylene group.
Additional confirmation of the structure of compound 13
was obtained from its 13C NMR spectrum, which contained
a highly deshielded signal at 162.8 ppm due to the lactone
carbonyl together with a signal at 157 ppm, assigned to a
carbon linked to oxygen, and a third signal at 39.8 ppm,
corresponding to the methylene group.
the H NMR spectrum showed a broad signal at 5.44 ppm,
due to the hydroxy proton, and the 13C NMR include a
deshielded signal at 150.9 ppm, which was assigned to the
carbon bearing the hydroxy group.
The different behaviour of ketoaldehyde 11a with respect to
its ketoester derivative 12b can be explained in terms of a
competition between three different processes (Scheme 4).
The formation of hemiacetals 20 or 22 from ketoaldehyde
11a via their respective enolates 19 and 21 should be
reversible processes, but enolate 21 can also give naphthol
14a by an intramolecular aldol reaction followed by
enolization and dehydration to allow the aromatization of
the B ring. The irreversible nature of this last transformation
is the reason for the displacement of all the equilibria to the
formation of compound 14a.
Benzylisochromanone 13 should result from the dehy-
dration of ketoacid 12a under the reaction conditions
employed; in a separate experiment ketoacid 12a was
heated under reflux for 2 h in toluene containing H2SO4
to give isochromanone 13 in 92% yield.24 Unfortunately,
when ketoacid 12a was esterified and a methanolic solution
of the resulting ketoester 12b23 containing sodium methox-
ide was stirred at room temperature for 3 h, the expected
naphthoquinone 2a was not obtained. The only product in
this reaction was the previously obtained benzylisochroma-
none 13.23
Our synthetic plan continued with the transformation of
naphthol 14a into hydroxyphenylnaphthoquinone 2a and
this was achieved easily in two steps. Treatment of 14a with
Fremy’s salt and potassium biphosphate in an aqueous
acetone solution gave a 68% yield of o-naphthoquinone
1
15a.8f The H NMR spectrum of this compound showed a
doublet for an aromatic proton at 8.03 ppm, a multiplet for
an aromatic protons at 7.58 ppm and a multiplet due to
seven aromatic protons and the proton of the double bond at
7.31–7.47 ppm. The 13C NMR spectrum showed two very
close signals at 180 and 179.1 ppm due to the carbonyl
groups. Finally, aqueous sodium hydroxide was added to a
methanolic solution of naphthoquinone 15a and the mixture
was stirred at room temperature for 15 min.12a This reaction
gave 93% yield of the desired hydroxynaphthoquinone 2a,5a
The easy transformation of ketoester 12b into benzyliso-
chromanone 13 can be explained in terms of a competition
between two irreversible processes (Scheme 3): cyclization
of enolate 16 to compound 13 and transformation of enolate
Scheme 3.

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488
Scheme 4.
which was identified by direct comparison with an authentic
sample of this compound.
MS 50 TC mass spectrometer. Thin layer chromatography
(tlc) was performed using Merck GF-254 type 60 silica gel
and dichloromethane/methanol mixtures as eluant; the tlc
spots were visualized with ultraviolet light or iodine vapour.
Column chromatography was carried out using Merck type
9385 silica gel. Solvents were purified as per Ref. 25.
Solutions of extracts in organic solvents were dried with
anhydrous sodium sulfate. Compounds 2a, 8a, 8b, 9a, 10a
and 12a, 12b, 13, 15a and 2a have been previously
prepared.
The potential of this new synthetic route was confirmed by
the successful preparation of hydroxyphenylnaphtho-
quinone 2b from ketoaldehyde 11b (Scheme 2). Compound
11b was easily and efficiently obtained by aldol conden-
sation of 1-indanone 7b and benzaldehyde, followed by the
regioselective hydrogenation of benzylideneindanone 8b,24
reduction of 9b and dehydration of the resulting mixture of
indanols and ozonolysis of benzylindene 10b. As expected,
the intramolecular aldol condensation of 11b provided
naphthol 14b, which was easily oxidized to o-naphtho-
quinone 15b. Finally, treatment of this compound with
H2SO4 afforded the desired 2-hydroxynaphthoquinone 2b.
1.1.1. (E)-2-Benzylideneindan-1-one (8a). To a solution of
benzaldehyde (2.44 mL, 24.06 mmol) in dry methanol was
added a solution of sodium methoxide (prepared by addition
of 66 mL of dry methanol to 157 mg of sodium) and a
solution of 1-indanone (3 g, 22.70 mmol) in dry methanol
(54 mL) dropwise at 0 8C under argon. The resulting
mixture was stirred at rt for 13 h. The reaction mixture
was then poured into water (100 mL) and the resulting
suspension was acidified by the addition of 2 M HCl. The
product was extracted into dichloromethane (3!100 mL).
The combined organic extracts were dried with anhydrous
sodium sulfate and concentrated to dryness in vacuo.
Crystallisation of the solid residue with MeOH yielded the
title compound (4.735 g, 95%) as white crystals. Mp 109–
In summary, we describe here the first total synthesis of
phenylketopropylbenzaldehydes in a process that allowed
us to develop novel chemistry in the field of quinones.
Oxidation of these aldehydes constitutes a new and efficient
method for the preparation of ketoacids 12. Dehydration of
the latter compounds constitutes a new and efficient method
to obtain 3-benzylisochromanones 13. Furthermore, the
intramolecular aldol condensation of ketoaldehydes 11
constitutes the first general, efficient synthesis of 3-phenyl-
naphthalen-2-ols (14), which were oxidized to 3-phenyl-
1,2-naphthoquinones (15) for the first time. Further
oxidation of the latter compounds is the last step of a new,
simple and efficient synthesis of 3-phenyl-2-hydroxy-1,4-
naphthoquinones (2).
1
111 8C (MeOH). IR (nꢀ, cmK1, NaCl): 1697 (C]O). H
NMR (d, ppm): 4.01 (s, 2H, –CH2–), 7.38–7.67 (m, 9H, 8!
Ar–H and CH]C), 7.90 (d, 1H, JZ7.5 Hz, Ar–H). 13C
NMR (d, ppm): 32.4 (CH2), 124.5 (CH), 126.2 (CH), 127.7
(CH), 129.0 (2!CH), 129.7 (CH), 130.8 (2!CH), 134.0
(CH), 134.7 (CH), 134.8 (C), 135.5 (C), 138.1 (C), 149.7
(C), 194.4 (C]O). MS (m/z, %): 220 (MC, 58), 219 [(MK
1)C, 100].
Work is now in progress to apply this synthetic route for
naphthoquinones to the synthesis of complex naphtho-
quinones, including benzofuronaphthoquinones 4, benzo-
pyronaphthoquinones 5 and indolonaphthoquinones 6.
1.1.2. 2-Benzylindan-1-one (9a). 10% Pd/C (32.5 mg) was
added to a deoxygenated solution of benzylideneindanone
8a (4.802 g, 21.80 mmol) in ethyl acetate (480 mL) and the
mixture was stirred under a hydrogen atmosphere (1 atm) at
rt for 75 min. After removal of the excess of hydrogen in
vacuo, the reaction mixture was filtered though celite, which
was eluted with ethyl acetate. The filtrate was concentrated
to dryness in vacuo to give a quantitative yield of the title
compound (4.62 g) as a transparent oil. IR (nꢀ, cmK1, NaCl):
1. Experimental
1.1. General
Melting points were determined on a Kofler Thermogerate
apparatus and are uncorrected. Infrared spectra were
recorded on a MIDAC FTIR spectrophotometer. Nuclear
magnetic resonance spectra were recorded, unless otherwise
specified, on a Bruker WM-250 apparatus, using deutero-
chloroform solutions containing tetramethylsilane as
internal standard. Mass spectra were obtained on a Kratos
1
1708 (C]O). H NMR (d, ppm): 2.67 (dd, 1H, JZ13.8,
10.4 Hz, –CH2–), 2.86 (dd, 1H, JZ16.9, 3.3 Hz, –CH2–),
3.01 (m, 1H, –CH–), 3.17 (dd, 1H, JZ16.9, 7.5 Hz, –CH2–),
3.42 (dd, 1H, JZ13.8, 3.8 Hz, –CH2–), 7.26–7.42 (m, 7H,
7!Ar–H), 7.58 (t, 1H, JZ7.4 Hz, Ar–H), 7.80 (d, 1H, JZ

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A. Martınez et al. / Tetrahedron 61 (2005) 485–492
489
7.4 Hz, Ar–H). 13C NMR (d, ppm): 32.2 (CH2), 37.0 (CH2),
48.9 (CH), 124.1 (CH), 126.4 (CH), 126.7 (CH), 127.5
(CH), 128.6 (2!CH), 129.0 (2!CH), 134.9 (CH), 136.7
(C), 139.7 (C), 153.7 (C), 207.9 (C]O). MS (m/z, %): 222
(MC, 51), 131 (100).
–CH2–), 6.16 (s, 1H, –CH]C–), 7.29–7.48 (m, 6H, 6!Ar–
H), 7.45 (m, 1H, Ar–H), 7.65 (m, 1H, Ar–H), 8.24 (m, 1H,
Ar–H). 13C NMR (d, ppm): 39.8 (–CH2–), 103.9 (–CH–),
120.1 (C), 125.2 (CH), 127.2 (CH), 127.8 (CH), 128.7 (2!
CH), 129.3 (2!CH), 129.5 (CH), 134.7 (CH), 135.7 (C),
137.3 (C), 157.0 (C–O), 162.8 (C]O). MS (m/z, %): 236
(MC, 44), 89 (11).
1.1.3. 2-Benzyl-1H-indene (10a). Small portions of NaBH4
(1.607 g, 42.50 mmol) were added every 15 min during 1 h
to a solution of benzylindanone 9a (1.18 g, 5.31 mmol) in
methanol (80 mL). The mixture was stirred at rt for 30 min
and poured into water (50 mL). The methanol was
evaporated in vacuo and the remaining suspension was
extracted with dichloromethane (3!100 mL). The com-
bined organic extracts were dried and concentrated to
dryness in vacuo. The resulting solid was immediately
mixed with 9 M H2SO4 (100 mL) and the stirred suspension
was heated under reflux in a dry atmosphere for 30 min.
20% aqueous NaOH was added to give a basic pH and the
suspension was extracted with dichloromethane (3!
100 mL). The combined organic extracts were dried and
concentrated to dryness in vacuo to give a 93% yield of the
The basic organic extracts were neutralized with concen-
trated HCl and the resulting suspension was extracted with
dichloromethane (3!100 mL). The combined organic
extracts were washed with water (2!100 mL), dried and
concentrated to dryness in vacuo to give 82% yield of the
ketoacid 12a (108 mg) as white crystals. Mp 133–135 8C
(MeOH). IR (nꢀ, cmK1, NaCl): 2931–2856 (OH), 1714
(COOH) 1693 (C]O). 1H NMR (d, ppm, CDCl3): 3.83 (s,
2H, CH2), 4.14 (s, 2H, CH2), 7.20–7.38 (m, 7H, 7!Ar–H),
7.49 (t, 1H, JZ7.1 Hz, Ar–H), 7.92 (dd, 1H, JZ7.6, 1.1 Hz,
Ar–H). 13C NMR (d, ppm, DMSO): 48.2 (CH2), 48.8 (CH2),
126.7 (CH), 127.2 (2!CH), 128.4 (2!CH), 130.1 (CH),
130.6 (CH), 132.3 (CH), 132.7 (CH), 135.2 (C), 136.1 (C),
137.2 (C), 168.4 (–CO2H), 205.0 (C]O). MS (m/z, %): 236
[(MK18)C, 19], 135 (100).
1
title compound (4.13 g) as a transparent oil H NMR (d,
ppm): 3.33 (s, 2H, CH2), 3.86 (s, 2H, CH2), 6.57 (s, 1H,
HC]C), 7.12–7.40 (m, 9H, 9!Ar–H). 13C NMR (d, ppm):
38.1 (CH2), 40.9 (CH2), 120.4 (CH), 123.7 (CH), 124.1
(CH), 126.4 (CH), 126.5 (CH), 128.0 (CH), 128.7 (2!CH),
129.1 (2!CH), 140.2 (C), 143.6 (C), 145.5 (C), 149.5 (C).
MS (m/z, %): 206 (MC, 30), 91 (100).
1.1.6. 2-(2-Oxo-3-phenylpropyl)benzoic acid methyl
ester (12b). A solution of ketoacid 12a (160 mg,
0.63 mmol) and concentrated sulfuric acid (1 mL) in
methanol (20 mL) was heated under reflux in a dry
atmosphere for 75 min. The methanol was evaporated in
vacuo and the residue was poured into saturated sodium
bicarbonate (50 mL). The suspension was extracted with
dichloromethane (3!50 mL). The combined organic layers
were dried and concentrated to dryness in vacuo. The solid
residue was submitted to column chromatography (eluent
AcOEt/hexane, 1:9) to give isochormanone 13 (0.09 mmol,
14% yield) and ketoester 12b (0.43 mmol, 68% yield) as a
yellow oil. IR (nꢀ, cmK1, NaCl): 1726 (C]O), 1655 (C]O).
1H NMR (d, ppm): 3.83 (s, 3H, OCH3), 3.87 (s, 2H, CH2),
4.11 (s, 2H, CH2), 7.11 (d, 1H, JZ7.5 Hz, Ar–H), 7.25–7.37
(m, 6H, 6!Ar–H), 7.45 (m, 1H, Ar–H), 8.03 (dd, 1H, JZ
7.8, 1.4 Hz, Ar–H). 13C NMR (d, ppm): 48.2 (CH2), 49.8
(CH2), 51.9 (OCH3), 126.9 (CH), 127.2 (CH), 128.6 (2!
CH), 129.2 (C), 129.7 (2!CH), 131.0 (CH), 132.3 (CH),
132.5 (CH), 134.4 (C), 136.7 (C), 167.4 (C]O), 205.2
(C]O). MS (m/z, %): 268 (MC, 1), 91 (100).
1.1.4. 2-(2-Oxo-3-phenylpropyl)benzaldehyde (11a). N2,
O2 and O3 were bubbled consecutively for 10, 10 and 2 min,
respectively, through a solution of indene 10a (200 mg,
0.97 mmol) in dichloromethane (30 mL) at K78 8C until
the persistent presence of a blue color due to the ozonide
was detected. O2 was then bubbled through for a further
10 min to destroy excess O3 and finally N2 was bubbled for
5 min. Dimethyl sulfide was added and the mixture was
stirred at K78 8C under argon for 4 h 30 min and at rt for
25 h. The solvent was removed in vacuo and the solid
residue was submitted to column chromatography (eluent:
AcOEt/hexane, 1:9) to yield 71% of the target compound
(164 mg) as a yellow oil. IR (nꢀ, cmK1, NaCl): 1706 (CHO,
C]O). 1H NMR (d, ppm): 3.95 (s, 2H, –CH2–), 4.14 (s, 2H,
–CH2–), 7.14 (d, 1H, JZ6.9 Hz, Ar–H), 7.30–7.55 (m, 7H,
7!Ar–H), 7.79 (m, 1H, Ar–H), 9.98 (s, 1H, –CHO). 13C
NMR (d, ppm): 46.9 (CH2), 50.1 (CH2), 127.1 (CH), 127.8
(CH), 128.8 (2!CH), 129.9 (2!CH), 132.8 (CH), 133.8
(CH), 134.3 (C), 134.5 (C), 135.2 (CH), 136.0 (C), 193.5
(C]O), 204.9 (CHO). MS (m/z, %): 238 (MC, 1), 91 (100).
HRMS: C16H14O2 (MC), calcd 238.0994; found 238.0989.
1.1.7. 3-Benzyl-isochromen-1-one (13). A mixture of
sodium methoxide (10.8 mg, 0.2 mmol) and ketoester 12b
(300 mg, 1.12 mmol) in dry methanol (10 mL) was heated
under reflux during 3 h. The reaction mixture was acidified
by adding 10% aq HCl and the resulting suspension was
extracted with dichloromethane (3!25 mL). The combined
organic extracts were washed with water (25 mL), dried and
concentrated to dryness in vacuo to give quantitative yield
of the title compound as a yellow oil.
1.1.5. 2-(2-Oxo-3-phenylpropyl)benzoic acid (12a) and 3-
benzylisochromen-1-one (13). 1.5 mL of the Jones reagent
(500 mg of CrO3, 1 mL H2O, 0.5 mL H2SO4) was added to
solution of ketoaldehyde 11a in acetone (12 mL) under a dry
atmosphere. The mixture was stirred at rt for 45 min,
isopropyl alcohol (1 mL) was added and the acetone was
evaporated in vacuo. The resulting suspension was extracted
with dichloromethane (3!75 mL) and the combined
organic layers were washed with 10% aq NaOH (3!
75 mL) and concentrated to dryness in vacuo. Isochroma-
none 13 was obtained in 18% yield as a yellow liquid. IR (nꢀ,
cmK1, NaCl): 1727 (C]O). 1H NMR (d, ppm): 3.85 (s, 2H,
1.1.8. 3-Phenylnaphthalen-2-ol (14a). A solution of
ketoaldehyde 11a (86 mg, 0.36 mmol) in 5% aq NaOH
(5 mL) was stirred under a dry atmosphere at rt for 2 h. The
reaction mixture was acidified by adding 10% aq HCl and
the resulting suspension was extracted with dichloro-
methane (3!25 mL). The combined organic extracts were
washed with water (25 mL), dried and concentrated to

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490
dryness in vacuo to give a quantitative yield of the target
compound as a white solid. Mp 87–89 8C (MeOH). IR (nꢀ,
1.1.12. 2-Benzyl-5-methoxyindan-1-one (9b). Benzyl-
ydeneindanone 8b was submitted to catalytic hydrogenation
under the same conditions as for 8a to give a quantitative
yield of the title compound as white crystals. Mp 102–
104 8C (MeOH). IR (nꢀ, cmK1, KBr): 1689 (C]O). 1H NMR
(d, ppm): 2.61–2.83 (m, 2H, –CH2–), 2.94–3.14 (m, 2H,
–CH2–), 3.38 (dd, JZ4.1, 13.9 Hz, 1H, –CH–), 3.85 (s, 3H,
–OMe), 6.82–6.91 (m, 2H, 2!ArH), 7.19–7.32 (m, 5H, 5!
ArH), 7.71 (d, JZ8.5 Hz, 1H, ArH). 13C NMR (d, ppm):
32.1 (CH2), 37.1 (CH2), 49.0 (CH), 55.5 (OMe), 109.6
(CH), 115.3 (CH), 125.6 (CH), 126.2 (CH), 128.4 (2!CH),
128.9 (2!CH), 129.7 (C), 139.7 (C), 156.5 (C), 165.4 (C),
205.9 (C]O). MS (m/z, %): 252 (MC, 33), 161 (100). Anal.
Calcd for C17H16O2, C: 80.93; H: 6.39. Found C: 81.09; H:
6.12.
1
cmK1, NaCl): 3457 (–OH). H NMR (d, ppm): 5.44 (br s,
1H, –OH), 7.35–7.68 (m, 8H, 8!Ar–H), 7.74–7.83 (m, 3H,
3!Ar–H). 13C NMR (d, ppm): 110.3 (CH), 124.0 (CH),
126.3 (CH), 126.6 (CH), 127.9 (CH), 128.2 (CH), 129.3
(CH), 129.4 (2!CH), 129.7 (2!CH), 130.6 (C), 134.4 (C),
137.0 (C), 150.9 (C–OH). MS (m/z, %): 220 (MC, 100).
Anal. Calcd for C16H12O, C: 87.25; H: 5.49. Found C:
87.14; H: 5.51.
1.1.9. 3-Phenyl-1,2-naphthoquinone (15a). A solution of
Fremy’s salt (682 mg, 2.54 mmol) and potassium biphos-
phate (120 mg, 0.88 mmol) in water (18 mL) was added to a
solution of naphthol 14a (80 mg, 0.34 mmol) in acetone
(10 mL). The suspension was stirred in a dry atmosphere at
rt for 1 h and the acetone was evaporated in vacuo. The pink
suspension was extracted with dichloromethane (3!
25 mL) and the combined organic layers were washed
with water (25 mL), dried and concentrated to dryness in
vacuo. The remaining solid residue was submitted to flash
column chromatography (eluent: AcOEt/hexane, 1:9) and
the target compound 15a was isolated (57 mg, 68% yield) as
a pink solid. Mp 125–127 8C (MeOH). IR (nꢀ, cmK1, NaCl):
1663 (C]O). 1H NMR (d, ppm): 7.31–7.47 (m, 8H, 7!Ar–
H and –CH]C–), 7.58 (m, 1H, Ar–H), 8.03 (d, 1H, JZ
7.6 Hz, Ar–H). 13C NMR (d, ppm): 128.4 (2!CH), 128.5
(2!CH), 128.9 (CH), 130.0 (CH), 130.1 (CH), 130.4 (CH),
130.8 (C), 134.1 (C), 135.3 (C), 136.0 (CH), 138.8 (C),
141.9 (CH), 179.1 (C]O), 180.0 (C]O). MS (m/z, %): 234
(MC, 4), 206 (100).
1.1.13. 2-Benzyl-5-methoxy-1H-indene (10b). Reaction of
benzylmethoxyindanone 9b (2.84 g, 11.27 mmol) with
NaBH4 and then with H2SO4, in a similar way to 10a,
gave 76% yield of the title compound (1.39 g) as a white
solid. Mp 64–66 8C (MeOH/Et2O). 1H NMR (d, ppm): 3.27
(s, 2H, CH2), 3.81 (s, 2H, CH2), 3.82 (s, 3H, OMe), 6.47 (s,
1H, ]CH), 6.81 (dd, JZ8.2 Hz, J0Z2.3 Hz, 1H, ArH), 6.98
(d, JZ1.3 Hz, 1H, ArH), 7.17–7.36 (m, 6H, 6!ArH). 13C
NMR (d, ppm): 37.9 (CH2), 40.8 (CH2), 55.5 (OMe), 110.4
(CH), 111.6 (CH), 120.3 (CH), 126.1 (CH), 127.1 (CH),
128.4 (2!CH), 128.8 (2!CH), 138.4 (C), 140.2 (C), 145.2
(C), 146.9 (C), 157.3 (C). MS (m/z, %): 236 (MC, 38), 145
(100). Anal. Calcd for C17H16O, C: 86.40; H: 6.82. Found C:
86.67; H: 6.69.
1.1.14. 2-(4-Methoxy-2-oxo-3-phenylpropyl)benzalde-
hyde (11b). Ozonolysis of compound 10b under the same
conditions as for 10a gave a 72% yield of the title compound
1.1.10. 2-Hydroxy-3-phenyl-[1,4]naphthoquinone (2a).
A suspension of quinone 14a (27 mg, 0.12 mmol), MeOH
(2 mL) and 20% aq NaOH (2 mL) was stirred under a dry
atmosphere at rt for 15 min. The mixture was acidified with
2 M HCl and extracted with dichloromethane (3!25 mL).
The combined organic extracts were washed with water
(25 mL), dried and concentrated to dryness in vacuo to yield
the target quinone 2a (0.11 g, 93% yield) as a red solid. Mp
47–49 8C (MeOH). IR (nꢀ, cmK1, NaCl): 3425 (–OH), 1710
(C]O), 1650 (C]O). 1H NMR (d ppm): 7.40–7.54 (m, 5H,
5!Ar–H), 7.72–7.85 (m, 2H, 2!Ar–H), 8.15–8.23 (m, 2H,
2!Ar–H). 13C NMR (d, ppm): 126.2 (CH), 127.3 (CH),
128.0 (2!CH), 128.7 (CH), 129.3 (C), 129.9 (C), 130.6
(2!CH), 133.0 (C), 133.2 (CH), 135.3 (CH), 152.2 (C–
OH), 181.9 (C]O), 183.1 (C]O). MS (m/z, %): 250 (MC,
5), 149 (100).
as a white solid. Mp 164–166 8C (MeOH). IR (nꢀ, cmK1
,
KBr): 1705 (C]O), 1718 (–CHO).1H NMR (d, ppm): 3.83
(s, 3H, –OMe), 3.93 (s, 2H, CH2), 4.09 (s, 2H, CH2), 6.64 (d,
JZ2.5 Hz, 1H, ArH), 6.92 (m, 1H, ArH), 7.26–7.36 (m, 5H,
5!ArH), 7.71 (d, JZ8.5 Hz, 1H, ArH), 9.84 (s, 1H, CHO).
13C NMR (d, ppm): 47.0 (CH2), 50.0 (CH2), 55.4 (OMe),
112.1 (CH), 118.7 (CH), 126.9 (–CH), 127.6 (C), 128.5 (2!
CH), 129.7 (2!CH), 134.3 (C), 137.9 (CH), 138.3 (C),
163.5 (C), 191.6 (CHO), 204.6 (C]O). MS (m/z, %): 268
(MC, 5), 91 (100). Anal. Calcd for C17H16O3, C: 76.10; H:
6.01. Found C: 69.91; H: 6.27.
1.1.15. 7-Methoxy-3-phenyl-naphthalen-2-ol (14b). In a
similar way to 14a, reaction of the ketoaldehyde 11b
(559 mg, 2.08 mmol) with 5% aq NaOH provided the title
compound (502 mg, 97%) as a white solid. Mp 164–166 8C
(MeOH). IR (nꢀ, cmK1, KBr): 3405 (OH).1H NMR (d, ppm):
3.94 (s, 3H, –OMe), 5.67 (s, 1H, OH), 7.05–7.10 (m, 2H,
2!ArH), 7.45–7.73 (m, 7H, 8!ArH). 13C NMR (d, ppm):
55.2 (OMe), 104.2 (CH), 109.4 (CH), 116.5 (CH), 124.2
(C), 127.6 (CH), 127.8 (C), 128.9 (2!CH), 129.1 (2!CH),
129.2 (CH), 129.2 (CH), 135.4 (C), 136.9 (C), 151.2 (C),
157.9 (C). MS (m/z, %): 250 (MC, 100). Anal. Calcd for
C17H14O2, C: 81.58; H: 5.64. Found C: 81.29; H: 6.47.
1.1.11. (E)-2-Benzylidene-5-methoxy-indan-1-one (8b).
In a similar way to 8a, reaction of methoxyindanone 7b
(4.0 g, 24.66 mmol) and benzaldehyde (2.7 mL,
26.17 mmol) gave 81% yield of the title compound as
white crystals. Mp 171–173 8C (MeOH). IR (nꢀ, cmK1, KBr):
1
1686 (C]O). H NMR (d, ppm): 3.90 (s, 3H, OMe), 3.98
(d, JZ1.0 Hz, 2H, CH2), 6.92–6.97 (m, 2H, HC]C and
ArH), 7.38–7.48 (m, 3H, 3!ArH), 7.59–7.66 (m, 3H, 3!
ArH), 7.84 (d, JZ8.4 Hz, 1H, ArH). 13C NMR (d, ppm):
32.4 (CH2), 55.6 (OMe), 109.6 (CH), 115.2 (CH), 126.1
(CH), 128.8 (2!CH), 129.3 (C), 130.5 (2!CH), 131.4 (C),
132.6 (CH), 135.2 (C), 135.5 (C), 152.5 (C), 165.2 (C),
192.7 (C]O). MS (m/z, %, CI): (251 [(MCC1), 100].
1.1.16. 7-Metoxy-3-phenyl-1,2-naphthoquinone (15b).
Reaction of naphthol 14b (194 mg, 0.78 mmol) with
Fremy’s salt (1.46 mg, 5.43 mmol) and potassium biphos-
phate (256 mg, 1.88 mmol) under the same conditions as for

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A. Martınez et al. / Tetrahedron 61 (2005) 485–492
491
(h) Sukumaran, K. B.; Harvey, R. G. B. J. Org. Chem. 1980,
45, 4407. (i) Ishii, H.; Hanaoka, T.; Asaka, T.; Harada, Y.;
Ikeda, N. Tetrahedron 1976, 32, 2693.
the oxidation of 14a, gave 63% yield of the title compound
(123 mg) as a pink solid. Mp 167–169 8C (MeOH). IR (nꢀ,
cmK1, KBr): 1662 (C]O), 1648 (C]O). 1H NMR (d,
ppm): 3.88 (s, 3H, OMe), 7.11 (m, 2H, ]CH and ArH),
7.29–7.55 (m, 7H, 7!ArH). 13C NMR (d, ppm): 55.8
(OMe), 114.3 (CH), 121.9 (CH), 128.2 (C), 128.2 (4!CH),
128.4 (CH), 131.7 (CH), 132.0 (C), 134.2 (C), 135.7 (C),
142.1 (CH), 161.3 (C), 178.7 (C]O), 179.6 (C]O). MS
(m/z, %): 264 (MC, 19), 236 (100). Anal. Calcd for
C17H12O3, C: 77.26; H: 4.58. Found C: 76.91; H: 4.60.
7. (a) Chauhan, S. M. S.; Kalra, B.; Mohapatra, P. P. J. Mol.
Catal. 1999, 137, 85. (b) Suresh, S.; Skaria, S.; Ponrathnam, S.
Synth. Commun. 1996, 26, 2113. (c) Krohn, K.; Rieger, H.;
Brueggmann, K. Synthesis 1990, 1141. (d) Suzuki, J.;
Watanabe, T.; Suzuki, S. Chem. Pharm. Bull. 1988, 36,
2204. (e) Lemaire, M.; Guy, A.; Roussel, J.; Guette, J. P.
Tetrahedron 1987, 43, 835. (f) Pinto, A. V.; Ferreira, V. F.;
Pinto, M. C. F. R. Synth. Commun. 1985, 15, 1177. (g) Arzeno,
H.; Barton, D. H. R.; Berge-Lurion, R. M.; Lusinchi, X.; Pinto,
B. M. J. Chem. Soc., Perkin Trans. 1 1984, 2069. (h) Horner,
L.; Weber, K. H. Chem. Ber. 1965, 1246.
1.1.17. 2-Hydroxy-7-methoxy-3-phenyl-[1,4]naphtho-
quinone (2b). Reaction of o-naphthoquinone 14b with
20% aq NaOH under the same conditions as for the
preparation of 14a gave 90% yield of the title compound as
8. For recent examples on the oxidation of naphthols to
naphthoquinones, see: (a) Chen, X.; Zhang, J. S.; Zhao, M.
Chin. Chem. Lett. 2001, 12, 297. (b) Ray, J. K.; Gupta, S.; Kar,
G. K.; Roy, B. C.; Lin, J.-M.; Amin, S. J. Org. Chem. 2000, 65,
8134. (c) Kumar, S.; Kim, T.-Y. J. Org. Chem. 2000, 65, 3883.
(d) Couladouros, E. A.; Strongilos, A. T. Tetrahedron Lett.
2000, 41, 535. (e) Buttery, J. H.; Wege, D. Aust. J. Chem.
1998, 51, 409. (f) Majetich, G.; Liu, S.; Fang, J.; Siesel, D.;
Zhang, Y. J. Org. Chem. 1997, 62, 6928.
a red solid. Mp 164–166 8C (MeOH/Benzene). IR (nꢀ, cmK1
,
KBr): 3327 (OH), 1660 (C]O), 1596 (C]O). 1H NMR (d,
ppm): 3.94 (s, 3H, –OMe), 7.21–7.25 (m, 1H, ArH), 7.37–
7.55 (m, 6H, 6!ArH), 8.10 (d, JZ8.8 Hz, 1H, ArH). 13C
NMR (d, ppm): 56.0 (OMe), 109.6 (CH), 121.2 (CH), 121.7
(C), 125.9 (C), 127.7 (2!CH), 128.5 (CH), 129.4 (CH),
129.9 (C), 130.6 (2!CH), 130.8 (C), 151.8 (C), 163.3 (C),
181.8 (C]O), 182.9 (C]O). MS (m/z, %): 280 (MC, 100).
Anal. Calcd for C17H12O3, C: 72.85; H: 4.32. Found C:
73.12; H: 3.97.
9. (a) Croux, S.; Maurette, M.-T.; Hocquaux, M.; Ananides, A.;
Braun, A. M.; Oliveros, E. New J. Chem. 1990, 14, 161–167.
(b) Min, D. M.; Croux, S.; Tournair, C.; Hocquaux, M.;
Jacquet, B.; Oliveros, E.; Maurette, M.-T. Tetrahedron 1990,
48, 1869–1882. (c) Bekaert, A.; Andrieux, J.; Plat, M.; Brion,
J.-D. Tetrahedron Lett. 1997, 38, 4219–4220.
Acknowledgements
We thank the Spanish Ministry of Science and Technology
and the Xunta de Galicia for financial support, and the latter
´ ´
for grants to Ana Martınez and to Marcos Fernandez.
10. (a) Lipshutz, B. H.; Shin, Y.-J. Tetrahedron Lett. 1998, 39,
7017. (b) Kost, A. N.; Terenin, V. I.; Yudin, L. G.; Sagitullin,
R. S. Khim. Geterotsiklich. Soedin. 1980, 1272. (c) Fields,
D. L. J. Org. Chem. 1971, 36, 3002.
11. For previous, low yielding methods for the synthesis of
3-phenyl-1,2-naphthoquinones, see: (a) Mackenzie, N. E.;
Surendrakumar, S.; Thomson, R. H.; Cowe, H. J.; Cox, P. J.
J. Chem. Soc., Perkin Trans. 1 1986, 2233. (b) Asselin, J.;
Brassard, P.; L’Ecuyer, P. Can. J. Chem. 1966, 44, 2563.
12. (a) Martinez, E.; Martinez, L.; Treus, M.; Estevez, J. C.;
Estevez, R. J.; Castedo, L. Tetrahedron 2000, 56, 6023.
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´
´
´
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