Methodology for the synthesis of 1,2-disubstituted arylnaphthalenes from α-tetralones

Article abstract of DOI:10.1016/j.tet.2006.01.013

α-Tetralones were initially converted into 1-bromo- dihydronaphthalene-2-carbaldehydes and 1-bromo-naphthalene-2-carbaldehydes. These precursors were then subjected to Suzuki coupling reactions to afford 1,2-disubstituted aryldihydronaphthalenes and 1,2-disubstituted arylnaphthalenes, respectively. The former products were oxidized with DDQ to give 1,2-disubstituted arylnaphthalenes.

Full text of DOI:10.1016/j.tet.2006.01.013

Tetrahedron 62 (2006) 2831–2844
Methodology for the synthesis of 1,2-disubstituted
arylnaphthalenes from a-tetralones
*
Simon S. Moleele, Joseph P. Michael and Charles B. de Koning
School of Chemistry, Molecular Sciences Institute, University of the Witwatersrand, Johannesburg, PO Wits 2050, South Africa
Received 28 October 2005; revised 13 December 2005; accepted 5 January 2006
Available online 30 January 2006
Abstract—a-Tetralones were initially converted into 1-bromo-dihydronaphthalene-2-carbaldehydes and 1-bromo-naphthalene-2-
carbaldehydes. These precursors were then subjected to Suzuki coupling reactions to afford 1,2-disubstituted aryldihydronaphthalenes
and 1,2-disubstituted arylnaphthalenes, respectively. The former products were oxidized with DDQ to give 1,2-disubstituted
arylnaphthalenes.
q 2006 Elsevier Ltd. All rights reserved.
1. Introduction
the binaphthol derivative 4 has been used as a chiral ligand
in the copper-catalysed Michael addition of dialkylzinc
reagents to cyclic a,b-unsaturated ketones.6 In addition, an
important contribution using binaphthols in organic syn-
thesis has come from the group of Shibasaki7,8 in that it has
been shown that a number of characterised heterobimetallic
asymmetric binaphthols are capable of catalyzing a variety
of reactions.
The synthesis of aromatic compounds containing biaryl
axes continues to be important as a result of the biological
activities associated with the biaryl natural products1 as well
as their use as ligands in transition metal catalysed
reactions.
For example, the naturally occurring compound (S)-
gossypol 1 (Fig. 1) contains a biaryl axis. Restricted
rotation about this axis imparts chirality to the molecule.
Pharmacologically it is known to be an oral antifertility
agent, and it shows potential for the treatment of HIV
infections, diabetic complications and cancer.2 Recent work
has also shown that the phenyl-naphthalene core is effective
in thyromimetics3a and shows high ceramide-mediated
proapoptotic activity on human breast cancer cells.3b
General methods for the synthesis of biaryl compounds
include the use of oxidative coupling methods.9 Otherwise,
traditional methods for the assembly of the biaryl axis such
as the Suzuki–Miyaura10,11 and Stille reactions are used.12
For the synthesis of suitably substituted biaryl compounds
HO
OH
CHO
R
R
OH
OH
HO
Apart from their interesting biological activity, biaryl
naphthalene compounds also find application as chiral
catalysts. The first and most frequently used chiral phosphine
ligand is BINAP 2 (Fig. 1). This is illustrated by the work of
Noyori who has shown that the ruthenium complexes of 2
are capable of effecting asymmetric hydrogenations and have
even found industrial applications.4,5
CHO
OH
(S)-1
(R)-2, R = PPh2
(R)-3, R = OH
The atropisomers of (1,10-binaphthyl)-2,20-diol 3 and its
derivatives (Fig. 1) are widely used in asymmetric synthesis,
either as ligands or as chiral auxiliaries. For example,
O
P
N
O
Keywords: Suzuki-Miyaura coupling reactions; Aromatization;
Arylnaphthalenes; a-Tetralone.
(S,R,R)-4
*
Corresponding author. Tel.: C27 11 7176724; fax: C27 11 7176749;
e-mail: dekoning@aurum.chem.wits.ac.za
Figure 1.
0040–4020/$ - see front matter q 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.01.013

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S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
both of these methods depend on the synthesis of suitably
substituted aromatic compounds and in the case of
arylnaphthalenes the synthesis depends on the availability
of suitably substituted naphthalenes.13 For example, the
arylnaphthalene 5 has been made by the coupling of
tolylboronic acid 6 and 7 (Scheme 1).14
R
R
R
R
ii
i
CHO
B(OH)2
Br
O
R=H; 8
R=H; 9
R
R=OMe; 15
R=OMe; 16
10a–d
B(OH)2
R
R
R
iii
Br
OH
6
R
CHO
P(O)(OEt)2
P(O)(OEt)2
Ar
Ar
1% Pd2(dba)3
R=H; 12a–d
R=OMe; 18a–d
R=H; 11a–d
R=OMe; 17a–d
7
5
NMe2
PCy2
R
R
2.4%
iv
v
OAc
OAc
R
R
Ar
Ar
2 equiv K3PO4
R=H; 14a–d
R=OMe; 20a–d
R=H; 13a–d
R=OMe; 19a–d
Scheme 1.
Our research group has been involved in the synthesis of
biaryl compounds and naphthalenes15 and in this paper we
report on the use of a-tetralones as suitable commercially
available substrates for the synthesis of simple arylnaphtha-
lenes. We show that a-tetralones can be used as ‘substitutes’
for naphthalenes as these are readily converted into the
naphthalene portion of the arylnaphthalene. Related results
on the use of tetralones for building substituted naphtha-
lenes have been reported by two other research group.3,16
v
OH
OH
Ar
Ar
12a–c
21a–c
Scheme 2. Reagents and Conditions: (i) DMF, PBr3, CH2Cl2, reflux, RZH,
70%; RZOMe, 63%; (ii) cat. Pd(PPh3)4, aqueous Na2CO3, boronic acid 10,
DME/EtOH, reflux; (iii) NaBH4, EtOH, rt; (iv) Ac2O, pyridine, reflux;
(v) DDQ, CH2Cl2, reflux; for yields see Table 1.
aryl 6,7-dimethoxycarbaldehydes 17a–d in good yields.
Reduction of the carbaldehydes 17a–d using sodium
borohydride in ethanol gave dimethoxydihydronaphthalene
alcohols 18a–d in very good yields. As in the previous
series, the resultant alcohols were then protected as their
esters to give 19a–d. The subsequent dimethoxydihydro-
naphthalene esters were then dehydrogenated as before to
the envisaged substituted biaryl dimethoxynaphthalenes
20a–d using DDQ in CH2Cl2 and the products were
obtained in satisfactory yields (Table 1).
2. Results and discussion
Following literature protocol, readily available a-tetralone 8
was converted into the known dihydronaphthalene 9 in good
yield as shown in Scheme 2.17,18 Using our well-developed
Suzuki–Miyaura reaction conditions we then attempted to
produce a number of aryldihydronaphthalenes. Reaction of
9 with catalytic Pd(PPh3)4 in the presence of boronic acids
10a–d and aqueous Na2CO3 and DME afforded the desired
Suzuki coupling products 11a–d in good to excellent
yields.19 Subsequently the products were then reduced to
alcohols 12a–d using sodium borohydride in ethanol. The
resultant alcohols 12a–d were protected as their esters using
acetic anhydride and pyridine to give 13a–d. Finally, all that
was required was the oxidation of dihydronaphthalenes
13a–d to afford the desired biaryl naphthalenes. The use of
2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in
CH2Cl2 afforded good yields of the desired arylnaphtha-
lenes 14a–d from 13a–d demonstrating that tetralones can
be used as substitutes for naphthalenes.
It has to be mentioned that an attempt was made to
aromatize some of the dihydronaphthalene carbaldehydes
11a–d using DDQ as reagent in CH2Cl2, as was done with
the dihydronaphthalene esters. Unfortunately, in all cases
only the starting material was obtained or uncharacterizable
products were obtained.
In order to try and decrease the number of steps required to
obtain the desired biaryl naphthalenes, the aromatization
reaction was attempted on the related alcohols 12a–c.
(Scheme 2). Three of the dihydronaphthalene alcohols
12a–c were aromatized using this methodology to afford
21a–c in good yields.
Dimethoxybromodihydronaphthalene-2-carbaldehyde 16
was synthesized from a different tetralone substrate, 6,7-
dimethoxytetralone 15, using DMF and potassium tribro-
mide in CH2Cl2 in a similar manner to that described for
tetralone 8. As shown in Scheme 2 the exposure of 16 to
boronic acids 10a–d under aqueous Suzuki coupling
reaction conditions in the presence of [Pd(PPh3)4] gave
As an alternative to produce the same arylnaphthalene
alcohols we decided to investigate aromatization of the
initial dihydronaphthalenes with alternative reagents. After

S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
2833
Table 1. Yields for Scheme 2
Entry
Ar
%
%
Entry
%
Entry
%
Entry
%
9/11a
9/11b
9/11c
9/11d
16/17a
16/17b
16/17c
16/17d
3,4,5-(MeO)C6H2
Naphthyl
Ph
83
11a/12a
11b/12b
11c/12c
11d/12d
17a/18a
17b/18b
17c/18c
17d/18d
100
94
94
94
12a/13a
12b/13b
12c/13c
12d/13d
18a/19a
18b/19b
18c/19c
18d/19d
98
94
82
94
80
89
88
88
13a/14a
13b/14b
13c/14d
13d/14d
19a/20a
19b/20b
19c/20c
19d/20d
78
95
93
100
74
78
12a/21a
12b/21b
12c/21c
82
79
77
93
100
78
88
87
2-MePh
3,4,5-(MeO)C6H2
Naphthyl
Ph
87
100
100
87
83
98
100
78
2-MePh
extensive experimentation with 9 it was found that careful
treatment of the substrate with selenium powder in a small
amount of DMSO for 5 min at 170 8C resulted in acceptable
yields of the desired product 22. The related monomethox-
ydihydronaphthalene 23 also gave the desired naphthalene
24 in good yield (72%). The remaining steps for the
production of a variety of 1-arylnaphthalenes were straight-
forward. Treatment of both 22 and 24 with the boronic acids
10a–d gave the desired naphthalenes 25a–d and 26a–d with
an aldehyde substituent in the 2-position. All the aldehydes
were then reduced with NaBH4 to give alcohols 21a–d as
well as the monomethoxynaphthalenes 27a–d (Table 2,
Scheme 3).
naphthalenes, as these reactions generally afford mixtures of
products, particularly if the naphthalene is substituted. For
example, bromination of 6,7-dimethoxy-2-naphthaldehyde
would not afford 24.
Specifically, we have been able to develop a two step
procedure for the synthesis of aryldihydronaphthalenes
11a–d and 17a–d from tetralones 8 and 15, which can be
converted into the corresponding arylnaphthalenes. In
addition, a two step procedure for the synthesis of
1-bromo-2-formylnaphthalenes (22 and 24) has been
developed. These products can be utilized in Suzuki–
Miyaura reactions to afford biaryl compounds.
Future work will entail the introduction of an oxygen
substituent in the ortho position of the boronic acid. This
will provide arylnaphthalenes such as 28 with two oxygen
containing substituents ortho to the biaryl axis. These will
be potential ligands for metal catalyzed reactions.
Table 2. Yields for Scheme 3
Entry
Ar
%
Entry
%
22/25a
22/25b
22/25c
22/25d
24/26a
24/26b
24/26c
24/26d
3,4,5-(MeO)C6H2
Naphthyl
Ph
94
89
87
94
80
74
90
71
25a/21a
25b/21b
25c/21c
25d/21d
26a/27a
26b/27b
26c/27c
26d/27d
82
93
91
95
89
95
2-MePh
3,4,5-(MeO)C6H2
Naphthyl
Ph
OH
OH
100
93
2-MePh
28
R
R
i
ii
R1
CHO
R1
CHO
B(OH)2
Br
3. Experimental
3.1. General
Br
R1=R=H 22
R1=R=H 9
R1=H; R=OMe; 23
R1=H; R=OMe; 24
R
10a–d
All reagents used were Analytical Grade Reagents from
Fluka and Aldrich. n-BuLi was obtained from Aldrich and
used as supplied. THF was dried by distillation from sodium
wire/benzophenone, DMF by distillation from CaH2. All
other solvents were BDH/HP high purity grade and distilled
before use. Thin-layer chromatography was carried out on
Macherey-Nagel Alugram Sil G/UV254 Plates, pre-coated
with 0.25 mm silica gel 60. Detection was done under ultra
violet light at 254 nm. For column chromatography,
Macherey-Nagel silica gel (32–63 mm) was used, with gel
mass 30 times that of sample, eluting with the stated solvent
mixtures. Melting points were determined on a Reichert hot-
stage microscope. Infrared spectra were run on the Bruker
Vector 22 Fourier Transform spectrometer. Absorption
maxima are reported in wavenumbers (cmK1), with
sZstrong, mZmedium and wZweak. NMR spectroscopic
analysis was done on an Ultrashield 300 MHz/54 Bohr
R
R
iii
OH
R1
CHO
R1
Ar
Ar
R1=R=H 25a–d
R1=H; R=OMe; 26a–d
R1=R=H 21a–d
R1=H; R=OMe; 27a–d
Scheme 3. Reagents and Conditions: (i) Se powder, DMSO, 170 8C, RZH,
69%; RZOMe, 72%; (ii) cat. Pd(PPh3)4, aqueous Na2CO3, boronic acid 10,
DME/EtOH, reflux; (iii) NaBH4, EtOH, rt; for yields see Table 2.
In conclusion, we have developed a new straight-forward
method for the synthesis of arylnaphthalenes where the
regiochemistry of the product is defined unambiguously
from the tetralone. This eliminates the difficulties of
preparing 1-bromonaphthalenes by direct bromination of
1
magnet. The frequency at which H NMR spectra were
reported was 300.131 MHz (rounded to 300 MHz) using

2834
S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
tetramethylsilane at 0.000 ppm as a standard. These spectra
are reported as parts per million (ppm), with sZsinglet,
dZdoublet, ddZdoublet of a doublet, tZtriplet, dtZdoublet
ofa triplet, mZmultiplet. The 13C NMR spectra werereported
at a frequency of 75.475 MHz (rounded to 75 MHz) using
CDCl3 at 77.00 ppm as a standard.
Extraction of the organic material into CH2Cl2 (3!100 mL)
was followed by drying the organic layer (MgSO4) before
being concentrated under reduced pressure to give a cream
white semi-solid 10a (0.43 g, 100%) that was not purified
further.
3.1.4. 1-Naphthylboronic acid 10b. In a similar manner to
that described above bromonaphthalene (0.50 g,
2.41 mmol) in THF (40 mL) was converted into boronic
acid 10b (0.26 g, 63%) using n-BuLi (1.90 mL,
12.66 mmol) and B(OMe)3 (0.81 mL, 7.24 mmol).
3.1.1. Bromo-3,4-dihydronaphthalene-2-carbaldehyde 9.
Dry DMF (8.02 mL, 103.2 mmol) in dry CH2Cl2 (50 mL)
was cooled to 0 8C and phosphorus tribromide (8.00 mL,
89.5 mmol) was added drop-wise. The mixture was stirred
at 0 8C for 1 h during which time a pale yellow suspension
was formed. A solution of a-tetralone 8 (4.58 mL, 5.03 g,
34.4 mmol) in dry CH2Cl2 (90 mL) was added and the
mixture was heated under reflux for 1 h. After cooling to
0 8C, aqueous NaHCO3 was added slowly until the
effervescence had subsided. Extraction of the organic
material into CH2Cl2 (3!100 mL) was followed by drying
the organic layer (MgSO4). The solution was filtered
through a Celite plug and evaporation of the excess solvent
resulted into brown oil. Column chromatography eluting
with 30% ethyl acetate/hexane gave the product 9 as a
brown solid (5.71 g, 70%) with identical spectroscopic data
to that described in the literature.17,18
3.1.5. Phenylboronic acid 10c. Boronic acid 10c, a cream
white semi-solid (1.47 g, 89%) was synthesized from
bromobenzene (1.43 mL, 13.58 mmol), n-BuLi (1.87 mL,
14.9 mmol) and B(OMe)3 (1.96 mL, 4.07 mmol) in a
similar way as described above.
3.1.6. o-Tolylboronic acid 10d. Using the same procedure
as described above 2-bromotoluene (1.40 mL, 11.63 mmol)
was converted to boronic acid 10d, a white solid (1.34 g,
85%).
3.1.7. 1-(3,4,5-Trimethoxyphenyl)-3,4-dihydronaphtha-
lene-2-carbaldehyde 11a. To [Pd(PPh3)4] (0.22 g,
0.19 mmol) was added a deoxygenated solution of 9
(0.46 g, 1.940 mmol) in DME (10 mL). This was followed
by a deoxygenated solution of boronic acid 10a (0.62 g,
2.91 mmol) in ethanol (5 mL), and then a deoxygenated
solution of aqueous sodium carbonate (1.77 g, 16.5 mmol in
8.2 mL water). The resultant mixture was heated under
reflux under nitrogen for 46 h over which time the solution
turned deep red. After allowing the mixture to cool to room
temperature, it was quenched with water (50 mL) and the
organic material was then extracted with CH2Cl2
(3!100 mL). The resultant organic extracts were com-
bined, dried (MgSO4), filtered through a Celite plug and the
excess solvent removed using a rotary evaporator. The
subsequent oil was purified by column chromatography
(30% ethyl acetate/hexane) to afford the desired product 11a
as a brown solid (4.80 g, 83%). MpZ112–114 8C; IR nmax
(cmK1) 1659 (s, C]O stretch), 1575, 1564 (s, C]C
stretch); 1H NMR d/ppm 9.65 (1H, s, CHO), 7.26–7.31 (2H,
m, 2!ArH), 7.19–7.16 (1H, m, ArH), 6.99–6.96 (1H, m,
ArH), 6.51 (2H, s, 2!ArH), 3.93 (3H, s, OCH3), 3.84 (6H,
s, 2!OCH3), 2.94–2.89 (2H, m, CH2), 2.71–2.65 (2H, m,
CH2); 13C NMR d/ppm 20.2 (CH2), 27.5 (CH2), 56.2
(2!OCH3), 60.9 (OCH3), 107.7 (2!ArCH), 126.7 (CH),
127.8 (CH), 128.3 (CH), 130.2 (CH), 130.7 (C), 134.2 (C),
134.8(C),138.0(C), 138.5(C),153.1(2!C), 154.2(C), 193.4
(CHO);MS(EI)m/z (%):325 (MC1, 22), 324 (MC, 100), 293
(22), 281 (52), 265 (18), 168 (31), 153 (25), 51 (11); HRMS
calculated for C20H20O4 MC 324.1362, found 324.1362.
3.1.2. 1-Bromo-6,7-dimethoxy-3,4-dihydronaphthalene-
2-carbaldehyde 16. Dry DMF (0.56 mL, 7.27 mmol) in dry
CH2Cl2 (20 mL) was cooled to 0 8C and phosphorus
tribromide (0.60 mL, 6.30 mmol) was added drop-wise.
The mixture was stirred at 0 8C for 2 h and a pale yellow
suspension was formed. A solution of 6,7-dimethoxy-a-
tetralone 15 (0.50 g, 2.42 mmol) in dry CH2Cl2 (30 mL) was
added and the mixture was stirred at reflux for 12 h. After
cooling to 0 8C, aqueous NaHCO3 was added slowly until
the effervescence had subsided. Extraction of the organic
material into CH2Cl2 (3!100 mL) was followed by drying
of the organic layer (MgSO4), filtration through a Celite
plug and evaporation of the excess solvent, which resulted
into a yellow oil. Column chromatography (30% ethyl
acetate/hexane) gave 16 as a yellow crystalline solid
(0.45 g, 63%). This decomposed on standing and was
therefore used immediately. IR nmax (cmK1) 1659 (s, C]O
1
stretch), 1601, 1589, 1549 (s, C]C stretch); H NMR d/
ppm 10.19 (1H, s, CHO), 7.42 (1H, s, Ar-H), 6.71 (1H, s,
Ar-H), 3.95 (3H, s, OMe), 3.94 (3H, s, OMe), 2.80–2.75
(2H, m, CH2), 2.64–2.58 (2H, m, CH2); 13C NMR d/ppm
23.0 (CH2), 27.1 (CH2), 56.1 (OCH3), 56.2 (OCH3), 110.5
(CH), 112.1 (CH), 125.6 (C), 132.4 (C), 133.0 (C), 139.2
(C), 147.7 (C), 151.5 (C), 192.9 (CHO); MS (EI) m/z (%):
298 (MC81Br, 94), 296 (MC79Br, 100), 286 (17), 206 (50),
265 (22), 189 (53), 188 (43), 178 (24), 174 (19), 150 (42),
145 (35), 115 (39), 102 (22), 63 (18); HRMS calculated for
C13H13O739Br MC 296.0048, found 296.0019.
3.1.3. 3,4,5-Trimethoxyphenylboronic acid 10a. To a
stirred solution of 1-bromo-3,4,5-trimethoxybenzene
(0.50 g, 2.02 mmol) in THF (30 mL) at K78 8C under
nitrogen was added n-BuLi (1.56 mL, 2.22 mmol) drop-
wise. The reaction mixture was stirred at K78 8C for 30 min
before trimethylborate (0.68 mL, 6.07 mmol) was added
and the mixture stirred for another 30 min at K78 8C. The
subsequent mixture was then allowed to warm to room
temperature before being acidified with aqueous 10% HCl.
3.1.8. 1-(1-Naphthyl)-3,4-dihydronaphthalene-2-carbal-
dehyde 11b. Using the same procedure as outlined above
11b, a light brown oil (0.55 g, 93%) was obtained from a
mixture of [Pd(PPh3)4] (0.25 g, 0.21 mmol), dihydro-
naphthalene 9 (0.50 g, 2.11 mmol), boronic acid 10b
(0.54 g, 3.16 mmol, in ethanol 5 mL) and aqueous sodium
carbonate (1.90 g, 17.9 mmol in 8.9 mL of water). IR nmax
(cmK1) 1660 (s, C]O stretch), 1607, 1561 (m, C]C
1
stretch); H NMR d/ppm 9.40 (1H, s, CHO), 7.92 (2H, t,

S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
2835
JZ8.8 Hz, 2!ArH), 7.59–7.34 (5H, m, 5!ArH),
7.31–7.24 (2H, m, 2!ArH), 6.95 (1H, t, JZ7.7 Hz, ArH),
6.64 (1H, d, JZ7.7 Hz, ArH), 3.02–3.08 (2H, m, CH2),
2.84–2.94 (1H, m, CH), 2.66–2.77 (1H, m, CH); 13C NMR
d/ppm 20.1 (CH2), 27.7 (CH2), 125.1 (CH), 125.9 (CH),
126.3 (CH), 126.8 (CH), 126.9 (CH), 127.9 (CH), 128.1
(CH), 128.4 (CH), 128.4 (CH), 128.9 (CH), 130.2 (CH),
132.6 (C), 132.9 (C), 133.5 (C), 135.0 (C), 135.8 (C), 138.1
(C), 153.0 (C), 193.0 (CHO); MS (EI) m/z (%): 285 (MC1,
62), 284 (MC, 100), 283 (89), 268 (27), 265 (39), 256 (62),
255 (89), 254 (33), 253 (68), 252 (73), 250 (27), 241 (27),
240 (43), 239 (67), 228 (33), 226 (22), 165 (21), 129 (22),
128 (73), 127 (39), 126 (42), 119 (22), 113 (20); HRMS
calculated for C21H16O MC 284.1201, found 284.1202.
(5 mL), and then a deoxygenated solution of aqueous
sodium carbonate (1.45 g, 13.7 mmol in 6.9 mL water). The
resultant mixture was refluxed under nitrogen for 64 h
during which time the mixture turned deep red. After
allowing it to cool down to room temperature, the mixture
was quenched with water (50 mL) and the organic material
extracted with CH2Cl2 (3!100 mL). The resultant organic
extracts were combined, dried (MgSO4), and then filtered
through a Celite plug and the excess solvent removed using
a rotary evaporator. The subsequent oil was purified by
column chromatography using 30% ethyl acetate/hexane as
eluent to afford carbaldehyde 17a as a yellow crystalline
solid (0.55 g, 88%). MpZ139–141 8C; IR nmax (cmK1
)
1652 (s, C]O stretch), 1603, 1581, 1556 (m, C]C stretch);
1H NMR d/ppm 9.59 (1H, s, CHO), 6.79 (1H, s, ArH), 6.52
(2H, s, 2!ArH), 6.49 (1H, s, ArH), 3.94 (3H, s, OCH3),
3.93 (3H, s, OCH3), 3.85 (6H, s, 2!OCH3), 3.65 (3H, s,
OCH3), 2.88–2.82 (2H, m, CH2), 2.70–2.64 (2H, m, CH2);
13C NMR d/ppm 20.9 (CH2), 27.8 (CH2), 56.3 (OCH3), 56.4
(OCH3), 56.6 (2!OCH3), 61.3 (OCH3), 108.1 (2!CH),
111.4 (CH), 112.4 (CH), 127.6 (C), 131.3 (C), 132.8 (C),
133.1 (C), 138.4 (C), 147.8 (C), 151.2 (C), 153.4 (2!C),
154.9 (C), 193.5 (CHO); MS (EI) m/z (%): 385 (MC1, 27),
384 (MC, 100), 372 (52), 371 (31), 370 (45), 369 (31), 368
(93), 366 (24), 353 (30), 343 (39), 337 (32), 195 (20), 181
(20), 28 (70); HRMS calculated for C22H24O6 MC
384.1573, found 384.1573.
3.1.9. 1-Phenyl-3,4-dihydronaphthalene-2-carbaldehyde
11c. In a similar manner as described above a mixture of
[Pd(PPh3)4] (0.25 g, 0.21 mmol), dihydronaphthalene 9
(0.50 g, 2.11 mmol), boronic acid 10c (0.39 g, 3.16 mmol,
in ethanol 7 mL) and aqueous sodium carbonate (1.90 g,
17.9 mmol in 8.9 mL of water) was used to synthesize
11c as a light brown crystalline solid (0.49 g, 100%).
MpZ68–71 8C; IR nmax (cmK1) 1658 (s, C]O stretch),
1607, 1596 (m, C]C stretch); 1H NMR d/ppm 9.63 (1H, s,
CHO), 7.50–7.47 (3H, m, 3!ArH), 7.35–7.30 (4H, m, 4!
ArH), 7.18–7.12 (1H, dt, JZ7.8, 1.9 Hz, ArH), 6.90 (1H, d,
JZ7.7 Hz, ArH), 2.97–2.92 (2H, m, CH2), 2.76–2.71 (2H,
m, CH2); 13C NMR d/ppm 20.2 (CH2), 27.5 (CH2) 126.6
(CH), 127.8 (CH), 128.2 (2!CH), 128.4 (2!CH), 130.2
(C), 130.4 (2!C), 134.3 (C), 135.0 (C), 135.2 (ArC), 138.6
(C), 154.4 (ArC), 193.4 (CHO); MS (EI) m/z (%): 234 (MC,
100), 233 (52), 205 (73), 202 (66), 189 (26), 178 (35), 165
(26), 128 (49), 127 (27), 78 (25), 29 (31); HRMS calculated
for C17H14O MC 234.1045, found 234.1045.19
3.1.12. 6,7-Dimethoxy-1-(1-naphthyl)-3,4-dihydro-
naphthalene-2-carbaldehyde 17b. Using the same pro-
cedure as outlined above, a mixture of [Pd(PPh3)4] (0.12 g,
0.10 mmol), dihydronaphthalene 16 (0.30 g, 1.01 mmol),
boronic acid 10b (0.26 g, 1.51 mmol, in ethanol 5 mL) and
aqueous sodium carbonate (0.91 g, 8.58 mmol in 4.5 mL of
water) was used to synthesize carbaldehyde 17b as a light
brown oil (0.28 g, 87%). IR nmax (cmK1) 1652 (s, C]O
stretch), 1604, 1557 (s, C]C stretch); 1H NMR d/ppm 9.44
(1H, s, CHO), 7.84 (2H, t, JZ9.0 Hz, 2!ArH), 7.51–7.27
(5H, m, 5!ArH), 6.74 (1H, s, ArH), 6.07 (1H, s, ArH), 3.84
(3H, s, OCH3), 3.26 (3H, s, OCH3), 2.94–2.76 (3H, m,
CH2CCH), 2.67–2.56 (1H, m, CH); 13C NMR d/ppm 20.7
(CH2), 27.5 (CH2), 55.8 (OCH3), 55.9 (OCH3), 110.9 (CH),
111.6 (CH), 124.9 (CH), 125.9 (CH), 126.3 (CH), 126.7
(CH), 127.6 (C), 128.3 (CH), 128.3 (CH), 128.8 (CH), 132.2
(C), 132.5 (C), 133.0 (C), 133.4 (C), 133.9 (C), 147.4 (C),
150.7 (C), 153.2 (C), 192.7 (CHO); MS (EI) m/z (%): 345
(MC1, 63), 344 (MC, 100), 315 (49), 313 (22), 262 (50),
239 (27), 232 (24), 226 (21), 205 (31), 189 (23), 128 (79),
119 (29), 115 (24), 85 (35), 83 (52); HRMS calculated for
C23H20O3 MC 344.1412, found 344.1412.
3.1.10. 1-(o-Tolyl)-3,4-dihydronaphthalene-2-carbalde-
hyde 11d. Similarly [Pd(PPh3)4] (0.24 g, 0.210 mmol), a
solution of dihydronaphthalene 9 (0.50 g, 2.11 mmol) in
DME (10 mL), a solution of boronic acid 10d (0.43 g,
3.16 mmol) in ethanol (5 mL), and a solution of aqueous
sodium carbonate (1.90 g, 17.9 mmol in 8.9 mL of water)
was used to synthesize carbaldehyde 11d as a yellow
crystalline solid (0.41 g, 78%). MpZ59–61 8C; IR nmax
(cmK1) 1660 (s, C]O stretch), 1606, 1599 (m, C]C
stretch); 1H NMR d/ppm 9.48 (1H, s, CHO), 7.35–7.25 (5H,
m, 5!ArH), 7.16 (1H, d, JZ6.9 Hz, ArH), 7.10 (1H, dt, JZ
7.8, 2.4 Hz, ArH), 6.73 (1H, d, JZ7.8 Hz, ArH), 2.94 (2H, t,
JZ8.0 Hz, CH2), 2.83–2.73 (1H, m, CH), 2.66–2.55 (1H,
CH), 2.08 (3H, s, CH3); 13C NMR d/ppm 19.6 (CH3), 19.8
(CH2), 27.5 (CH2), 125.7 (CH), 126.7 (CH), 127.5 (CH),
127.9 (CH), 128.5 (CH), 130.2 (CH), 130.2 (CH), 130.5
(CH), 134.3 (C), 134.4 (C), 134.8 (C), 136.7 (C), 138.4 (C),
154.2 (C), 193.1 (CHO); MS (EI) m/z (%): 249 (MC1, 23),
248 (MC, 74), 247 (35), 233 (100), 229 (28), 215 (51), 203
(51), 202 (53); HRMS calculated for C18H16O MC
248.1201, found 248.1198.
3.1.13. 6,7-Dimethoxy-1-phenyl-3,4-dihydronaphtha-
lene-2-carbaldehyde 17c. In a similar manner as described
above [Pd(PPh3)4] (0.12 g, 0.10 mmol), dihydronaphthalene
16 (0.30 g, 1.01 mmol), boronic acid 10c (0.18 g,
1.51 mmol, in ethanol 5 mL) and aqueous sodium carbonate
(0.91 g, 8.58 mmol in 4.3 mL of water) afforded 17c as a
yellow solid (0.22 g, 83%). MpZ114–117 8C; IR nmax
(cmK1) 1650 (s, C]O stretch), 1605, 1557 (s, C]C
stretch); 1H NMR d/ppm 9.53 (1H, s, CHO), 7.48–7.45 (3H,
m, 3!ArH), 7.32–7.29 (2H, m, 2!ArH), 6.81 (1H, s, ArH),
6.39 (1H, s, ArH), 3.95 (3H, s, OCH3), 3.61 (3H, s, OCH3),
2.90–2.85 (2H, m, CH2), 2.72–2.68 (2H, m, CH2); 13C NMR
3.1.11. 6,7-Dimethoxy-1-(3,4,5-trimethoxyphenyl)-
3,4-dihydronaphthalene-2-carbaldehyde 17a. To
[Pd(PPh3)4] (0.19 g, 0.16 mmol) was added a deoxygenated
solution of dihydronaphthalene 16 (0.48 g, 1.62 mmol) in
DME (10 mL). This was followed by a deoxygenated
solution of boronic acid 10a (0.51 g, 2.42 mmol) in ethanol

2836
S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
d/ppm 20.4 (CH2), 27.4 (CH2), 55.9 (2!OCH3), 110.9
(CH), 111.9 (CH), 127.1 (C), 128.4 (2!CH), 128.6 (CH),
130.4 (2!CH), 132.4 (C), 132.6 (C), 135.4 (C), 147.2 (C),
150.6 (C), 154.6 (C), 192.9 (CHO); MS (EI) m/z (%): 295
(MC1, 26), 294 (MC, 100), 293 (21), 265 (22), 189 (15),
178 (19); HRMS calculated for C19H18O3 MC 294.1256,
found 294.1256.
(1H, m, ArH), 6.90 (1H, t, JZ7.5 Hz, ArH), 6.41 (1H, d,
JZ7.7 Hz, ArH), 3.92 (2H, s, CH2OH), 3.08–3.02 (2H, m,
CH2), 2.73–2.65 (2H, m, CH2); 13C NMR d/ppm 25.2
(CH2), 28.4 (CH2), 63.8 (CH2OH), 125.5 (CH), 125.7 (CH),
125.9 (CH), 126.1 (CH), 126.3 (CH), 126.4 (CH), 126.9
(CH), 127.2 (CH), 127.5 (CH), 127.7 (CH), 128.3 (CH),
132.6 (C), 133.7 (C), 133.9 (C), 135.3 (C), 135.9 (C), 137.7
(C), (one quaternary carbon missing); MS (EI) m/z (%): 286
(MC, 21), 268 (32), 267 (45), 255 (41), 253 (62), 251 (77),
249 (19), 239 (24), 238 (64), 229 (19), 228 (24), 225 (31),
215 (29), 165 (28), 152 (21), 141 (36), 129 (50), 128 (100),
127 (52), 115 (55), 77 (21), 31 (42); HRMS calculated for
C21H18O MC 286.1358, found 286.1356.
3.1.14. 6,7-Dimethoxy-1-(o-tolyl)-3,4-dihydronaphtha-
lene-2-carbaldehyde 17d. Similarly [Pd(PPh3)4] (0.20 g,
0.11 mmol), dihydronaphthalene 16 (0.50 g, 1.68 mmol) in
DME (10 mL), boronic acid 10d (0.36 g, 2.52 mmol, in
ethanol 10 mL) and aqueous sodium carbonate (1.56 g,
14.30 mmol in 7.4 mL of water) afforded carbaldehyde 17d
as a light brown oil (0.51 g, 98%). IR nmax (cmK1) 1656 (s,
3.1.17. (1-Phenyl-3,4-dihydronaphthalen-2-yl)methanol
12c. Using the same procedure as outlined above, NaBH4
(0.03 g, 0.19 mmol) in EtOH (10 mL) carbaldehyde 11c
(0.17 g, 0.72 mmol) afforded alcohol 12c as a yellow oil
(0.16 g, 94%). IR nmax (cmK1) 3386 (s, broad, OH stretch),
1
C]O stretch), 1606 (m, C]C stretch); H NMR d/ppm
9.41 (1H, s, CHO), 7.35–7.25 (3H, m, 3!ArH), 7.16 (1H, d,
JZ7.4 Hz, ArH), 6.79 (1H, s, ArH), 6.24 (1H, s, ArH), 3.93
(3H, s, OCH3), 3.57 (3H, s, OCH3), 2.90–2.83 (2H, m, CH2),
2.78–2.73 (1H, m, CH), 2.64–2.55 (1H, m, CH), 2.08 (3H, s,
CH3); 13C NMR d/ppm 19.6 (CH3), 19.9 (CH2), 27.4 (CH2),
55.9 (2!OCH3), 110.9 (CH), 111.0 (CH), 125.7 (CH),
126.9 (C), 128.5 (CH), 130.2 (CH), 130.4 (CH), 132.4 (C),
132.5 (C), 134.9 (C), 136.6 (C), 147.6 (C), 150.7 (C), 154.5
(C), 192.8 (CHO); MS (EI) m/z (%): 308 (MC, 100), 249
(16), 108 (31), 58 (20); HRMS calculated for C20H20O3 MC
308.1412, found 308.1396.
1
1654, 1598 (m, C]C stretch); H NMR d/ppm 7.37–7.29
(3H, m, 3!ArH), 7.13–7.11 (3H, m, 3!ArH), 7.08–7.06
(1H, dd, JZ7.3, 1.1 Hz, ArH), 6.99 (1H, t, JZ7.2 Hz, ArH),
6.60 (1H, d, JZ7.6 Hz, ArH), 4.02 (2H, s, CH2OH), 2.86
(2H, dd, JZ8.4, 7.5 Hz, CH2), 2.51 (2H, dd, JZ8.4, 7.5 Hz,
CH2); 13C NMR d/ppm 25.0 (CH2), 28.1 (CH2), 63.3
(CH2OH), 126.0 (CH), 126.1 (CH), 126.7 (CH), 126.9 (CH),
127.0 (CH), 128.2 (2!CH), 129.8 (2!CH), 135.5 (C),
135.8 (C), 135.9 (C), 136.1 (C), 138.3 (C); MS (EI) m/z (%):
237 (MC1, 20), 236 (MC, 100), 235 (20), 234 (62), 233
(33), 224 (24), 218 (38), 217 (36), 215 (24), 208 (36), 205
(77), 204 (25), 203 (46), 202 (52), 189 (21), 179 (26), 178
(36), 165 (23), 159 (21), 130 (23), 129 (34), 128 (20), 127
(22), 115 (35), 105 (23), 101 (23), 91 (76), 77 (26); HRMS
calculated for C17H16O MC 236.1201, found 236.1201.
3.1.15.
[1-(3,4,5-Trimethoxyphenyl)-3,4-dihydro-
naphthalen-2-yl]methanol 12a. To a solution of carbalde-
hyde 11a (0.51 g, 1.57 mmol) in ethanol (30 mL) was added
NaBH4 (0.07 g, 1.96 mmol). The reaction mixture was
stirred at room temperature for 2 h after which time it turned
cream white. The mixture was then extracted with CH2Cl2
(3!100 mL). The organic extracts were combined, dried
(MgSO4), and then filtered through a Celite plug and
concentrated in vacuo. The subsequent colourless oil was
purified by column chromatography using 30% ethyl
acetate/hexane as eluent to afford 12a as a white crystalline
3.1.18. [1-(o-Tolyl)-3,4-dihydronaphthalen-2-yl]metha-
nol 12d. Similarly using NaBH4 (0.05 g, 1.41 mmol) in
EtOH (10 mL) carbaldehyde 11d (0.32 g, 1.13 mmol) was
reduced to alcohol 12d, a white semi-solid (0.30 g, 94%). IR
nmax (cmK1) 3416 (s, broad, OH stretch), 1629 (m, C]C);
1H NMR d/ppm 7.26–6.99 (7H, m, 7!ArH), 6.50 (1H, d,
JZ7.6 Hz, ArH), 3.98 (2H, s, CH2OH), 2.93 (2H, dd,
JZ8.3, 7.7 Hz, CH2), 2.56 (2H, dd, JZ8.5, 7.5 Hz, CH2),
2.06 (3H, s, ArCH3); 13C NMR d/ppm 19.4 (CH2), 24.9
(CH2), 28.3 (CH3), 63.6 (CH2OH), 125.5 (CH), 125.8 (CH),
126.4 (CH), 126.8 (CH), 127.2 (CH), 127.4 (CH), 129.9
(CH), 130.1 (CH), 135.1 (C), 135.4 (C), 135.5 (C), 135.7
(C), 136.8 (C), 137.7 (C); MS (EI) m/z (%): 251 (MC1, 40),
250 (MC, 100), 235 (66), 232 (26), 219 (59), 218 (27), 217
(74), 216 (20), 215 (44), 204 (38), 203 (47), 202 (53), 179
(23), 178 (27), 159 (30), 129 (36), 128 (25), 119 (34), 115
(29), 105 (52), 101 (20), 91 (43), 43 (39); HRMS calculated
for C18H18O MC 250.1358, found 250.1358.
solid (0.51 g, 100%). MpZ115–116 8C; IR nmax (cmK1
)
3421 (m, broad, OH stretch), 1583, 1507 (s, C]C stretch);
1H NMR d/ppm 7.17–7.02 (3H, m, 3!ArH), 6.72 (1H, dd,
JZ7.3, 1.0 Hz, ArH), 6.39 (2H, s, 2!ArH), 4.12 (2H, s,
CH2OH), 3.89 (3H, s, OCH3), 3.80 (6H, s, 2!OCH3), 2.90
(2H, dd, JZ8.4, 7.6 Hz, CH2), 2.54 (2H, dd, JZ8.4, 7.5 Hz,
CH2), 1.85 (1H, s, CH2OH); 13C NMR d/ppm 25.1 (CH2),
28.1 (CH2), 55.9 (2!OCH3), 60.8 (OCH3), 63.5 (CH2OH),
106.9 (2!CH), 126.1 (CH), 126.2 (CH), 126.8 (CH), 127.1
(CH), 133.9 (C), 135.4 (C), 135.8 (C), 135.9 (C), 136.8 (C),
153.0 (2!C), (one quaternary carbon missing); MS (EI) m/z
(%): 327 (MC1, 22), 326 (MC, 100), 297 (25), 295 (27) 181
(10), 168 (24), 165 (14), 129 (21); HRMS calculated for
C20H22O4 MC 326.1518, found 326.1519.
3.1.16.
[1-(1-Naphthyl)-3,4-dihydronaphthalen-2-
3.1.19. [6,7-Dimethoxy-1-(3,4,5-trimethoxyphenyl)-3,4-
dihydronaphthalen-2-yl]methanol 18a. In a similar man-
ner as described above, NaBH4 (0.06 g, 1.72 mmol) in
EtOH (10 mL) was used to reduce carbaldehyde 17a
(0.53 g, 1.34 mmol) to alcohol 18a, a white semi-solid
(0.46 g, 87%). IR nmax (cmK1) 3517 (s, broad, OH stretch),
1651 (m, C]C stretch); 1H NMR d/ppm 6.66 (1H, s, ArH),
6.33 (2H, s, 20 and 60-H), 6.24 (1H, s, ArH), 4.04 (2H, s,
CH2OH), 3.83 (3H, s, OCH3), 3.81 (3H, s, OCH3), 3.75
yl]methanol 12b. Similarly using NaBH4 (0.05 g,
1.32 mmol) in EtOH (10 mL) carbaldehyde 11b (0.30 g,
1.06 mmol) was reduced to alcohol 12b, a cream white
semi-solid (0.29 g, 94%). IR nmax (cmK1) 3384 (s, broad,
OH stretch), 1648, 1588, 1576 (m, C]C stretch); 1H NMR
d/ppm 7.87 (2H, t, JZ7.3 Hz, 2!ArH), 7.68 (1H, d,
JZ8.5 Hz, ArH), 7.54–7.43 (2H, m, 2!ArH), 7.38–7.29
(2H, m, 2!ArH), 7.24–7.20 (1H, m, ArH), 7.07–7.12

S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
2837
(6H, s, 2!OCH3), 3.54 (3H, s, OCH3), 2.78 (2H, dd, JZ
8.4, 7.6 Hz, CH2), 2.46 (2H, dd, JZ8.5, 7.6 Hz, CH2); 13C
NMR d/ppm 25.5 (CH2), 27.9 (CH2), 55.9 (OCH3), 56.1
(3!OCH3), 60.9 (OCH3), 63.8 (CH2OH), 106.9 (20 and
60-C), 110.7 (CH), 110.9 (CH), 128.5 (C), 128.6 (C), 133.6
(C), 133.9 (C), 135.8 (C), 136.9 (C), 146.9 (C), 147.9 (C),
153.4 (2!C); MS (EI) m/z (%): 387 (MC1, 63), 386
(MC, 100), 357 (22), 355 (44), 189 (21), 164 (18), 152 (16),
31 (12); HRMS calculated for C22H24O6 MC 386.1729,
found 386.1729.
(C), 147.9 (C); MS (EI) m/z (%): 311 (MC1, 19), 310 (MC,
80), 309 (23), 308 (75), 294 (33), 293 (35), 279 (56), 191
(26), 189 (26), 166 (40), 148 (100), 83 (30), 57 (38), 43 (27),
41 (22); HRMS calculated for C20H22O3 MC 310.1569,
found 310.1569.
3.1.23.
[1-(3,4,5-Trimethoxyphenyl)-3,4-dihydro-
naphthalen-2-yl]methyl acetate 13a. A mixture of alcohol
12a (0.38 g, 1.16 mmol), pyridine (5 mL) and acetic
anhydride (5 mL) was refluxed under nitrogen for 16 h
during which time the mixture turned black. After cooling to
room temperature, excess solvent was removed under
reduced pressure and the resultant oil purified by column
chromatography using 30% ethyl acetate/hexane as eluent
to afford the acetate 13a as yellow crystalline solid (0.42 g,
98%). MpZ81–83 8C; IR nmax (cmK1) 1734 (s, C]O
stretch), 1584 (s, C]C stretch); 1H NMR d/ppm 7.16–7.07
(3H, m, 3!ArH), 6.74 (1H, d, JZ7.3 Hz, ArH), 6.41 (2H, s,
20 and 60-H), 4.61 (2H, s, CH2OAc), 3.90 (3H, s, OCH3),
3.82 (6H, s, 2!OCH3), 2.92 (2H, dd, JZ8.4, 7.7 Hz, CH2),
3.1.20. [6,7-Dimethoxy-1-(1-naphthyl)-3,4-dihydro-
naphthalen-2-yl]methanol 18b. Similarly NaBH4 (0.03 g,
0.19 mmol) in EtOH (10 mL), reduced carbaldehyde 17b
(0.25 g, 0.73 mmol) to alcohol 18b, obtained as a light
brown oil (0.25 g, 100%). IR nmax (cmK1) 3481 (m, broad,
1
OH stretch), 1604 (m, C]C stretch); H NMR d/ppm 7.76
(2H, t, JZ7.3 Hz, 2!ArH), 7.58 (1H, d, JZ8.4 Hz, ArH),
7.42–7.31 (2H, m, 2!ArH), 7.27–7.19 (2H, m, 2!ArH),
6.67 (1H, s, ArH), 5.89 (1H, s, ArH), 3.78 (2H, s, CH2OH),
3.77 (3H, s, OCH3), 3.23 (3H, s, OCH3), 2.91–2.84 (2H, m,
CH2), 2.59–2.54 (2H, m, CH2); 13C NMR d/ppm 25.3
(CH2), 28.1 (CH2), 55.8 (OCH3), 55.9 (OCH3), 63.7
(CH2OH), 110.5 (CH), 110.9 (CH), 125.4 (CH), 125.7
(CH), 125.8 (CH), 126.1 (CH), 127.3 (CH), 127.6 (CH),
128.2 (CH), 128.8 (C), 132.5 (C), 133.4 (C), 133.6 (C),
135.5 (2!C), 135.9 (C), 146.9 (C), 147.9 (C); MS (EI) m/z
(%): 347 (MC1, 43), 346 (MC, 100), 345 (21), 344 (53),
330 (25), 315 (34), 239 (24), 226 (18), 215 (19); HRMS
calculated for C23H22O3 MC 346.1569, found 346.1569.
2.46 (2H, dd, JZ8.4, 7.7 Hz, CH2), 2.07 (3H, s, OAc); 13
C
NMR d/ppm 20.9 (CH2), 25.4 (OAc), 27.9 (CH2), 56.0 (2!
OCH3), 60.8 (OCH3), 65.6 (CH2OAc), 106.8 (20 and 60-C),
126.3 (CH), 126.3 (CH), 127.1 (CH), 127.2 (CH), 131.0 (C),
133.4 (C), 135.4 (C), 135.6 (C), 137.0 (C), 138.3 (C), 153.1
(2!C), 170.9 (OCOCH3); MS (EI) m/z (%): 369 (MC1,
11), 368 (MC, 51), 309 (12), 308 (18), 293 (22), 278 (33),
277 (100), 246 (17); HRMS calculated for C22H24O5 MC
368.1624, found 368.1620.
3.1.24.
[1-(1-Naphthyl)-3,4-dihydronaphthalen-2-
3.1.21. (6,7-Dimethoxy-1-phenyl-3,4-dihydronaphtha-
len-2-yl)methanol 18c. Using the same procedure as
described above, NaBH4 (0.03 g, 0.81 mmol) in EtOH
(10 mL) reduced aldehyde 17c (0.17 g, 0.65 mmol) to
alcohol 18c obtained as a light yellow oil (0.20 g, 100%).
IR nmax (cmK1) 3449 (m, broad, OH stretch), 1573, (m,
C]C stretch); 1H NMR d/ppm 7.41–7.30 (3H, m, 3!ArH),
7.18–7.15 (2H, m, 2!ArH), 6.72 (1H, s, ArH), 6.19 (1H, s,
ArH), 4.06 (2H, s, CH2OH), 3.88 (3H, s, OCH3) 3.56 (3H, s,
OCH3), 2.85 (2H, t, JZ8.1 Hz, CH2), 2.54 (2H, t, JZ
8.1 Hz, CH2); 13C NMR d/ppm 25.5 (CH2), 28.0 (CH2), 55.8
(OCH3), 55.9 (OCH3), 63.7 (CH2OH), 110.8 (CH), 110.9
(CH), 127.1 (CH), 128.2 (2!CH), 128.5 (C), 128.8 (C),
129.9 (2!CH), 133.8 (C), 135.8 (C), 138.4 (C), 146.9 (C),
147.9 (C); MS (EI) m/z (%): 296 (MC, 12), 263 (14), 219
(69), 154 (43), 131 (22), 87 (23), 57 (100), 41 (23); HRMS
calculated for C19H20O3 MC 296.1412, found 296.1403.
yl]methyl acetate 13b. In a similar manner as described
above alcohol 12b (0.25 g, 0.87 mmol) gave 13b as a yellow
oil (0.27 g, 94%). IR nmax (cmK1) 1734 (s, C]O stretch),
1593 (m, C]C stretch); 1H NMR d/ppm 7.86–7.82 (2H, m,
2!ArH), 7.65 (1H, d, JZ8.5 Hz, ArH), 7.52–7.42 (2H, m,
2!ArH), 7.39–7.29 (2H, m, 2!ArH), 7.18 (1H, d,
JZ7.3 Hz, ArH), 7.08 (1H, t, JZ7.4 Hz, ArH), 6.87
(1H, t, JZ7.5 Hz, ArH), 6.41 (1H, d, JZ7.7 Hz, ArH), 4.42
(2H, s, CH2OAc), 3.02(2H, m, CH2), 2.60–2.54 (2H, m, CH2),
1.92 (3H, s, OAc); 13C NMR d/ppm 20.8 (CH2), 25.5 (OAc),
28.2 (CH2), 65.6 (CH2OAc), 125.6 (CH), 125.9 (CH), 126.0
(CH), 126.1 (CH), 126.2 (CH), 126.3 (CH), 127.3 (2!CH),
127.6 (CH), 128.0 (CH), 128.4 (CH), 132.5 (C), 133.0 (C),
133.8 (C), 135.3 (C), 135.6 (C), 135.8 (C), 136.3 (C), 171.0
(OCOCH3); MS (EI) m/z (%): 329 (MC1, 25), 328 (MC, 77),
270 (29), 269 (100), 268 (53), 267 (56), 266 (58), 265 (74), 263
(21), 255 (41), 254 (52), 253 (99), 252 (97), 249 (22), 241 (25),
240 (31), 239 (67), 228 (25), 226 (23), 165 (23), 141 (60), 133
(20), 129 (32), 128 (29), 127 (25), 126 (51), 117 (26), 115 (28),
91 (30), 43 (63); HRMS calculated for C23H20O2 MC
328.1463, found 328.1463.
3.1.22. [6,7-Dimethoxy-1-(o-tolyl)-3,4-dihydronaphtha-
len-2-yl]methanol 18d. Similarly NaBH4 (0.05 g,
1.29 mmol) in EtOH (10 mL) was used to reduce aldehyde
17d (0.32 g, 1.04 mmol) to alcohol 18d obtained as a yellow
semi-solid (0.28 g, 87%). IR nmax (cmK1) 3508 (m, broad,
OH stretch), 1605, 1573 (m, C]C stretch); 1H NMR d/ppm
7.27–7.19 (3H, m, 3!ArH), 7.06 (1H, d, JZ6.7 Hz, ArH),
6.74 (1H, s, ArH), 6.06 (1H, s, ArH), 3.97 (2H, s, CH2OH),
3.87 (3H, s, OCH3), 3.54 (3H, s, OCH3), 2.89–2.84 (2H, m,
CH2), 2.57–2.52 (2H, m, CH2), 2.06 (3H, s, ArCH3); 13C
NMR d/ppm 19.5 (CH3), 25.2 (CH2), 28.1 (CH2), 55.9
(OCH3), 56.0 (OCH3), 63.8 (CH2OH), 110.0 (CH), 111.1
(CH), 125.8 (CH), 127.5 (CH), 128.2 (C), 128.4 (C), 130.0
(2!C), 133.5 (C), 135.0 (C), 136.7 (C), 137.8 (C), 147.2
3.1.25. (1-Phenyl-3,4-dihydronaphthalen-2-yl)methyl
acetate 13c. Similarly alcohol 12c (0.25 g, 1.06 mmol
afforded acetate 13c as a yellow oil (0.24 g, 82%). IR nmax
(cmK1) 1735 (s, C]O stretch), 1656, 1598 (m, C]C
stretch); 1H NMR d/ppm 7.39–7.33 (3H, m, 3!ArH), 7.18–
7.09 (5H, m, 5!ArH), 7.02 (1H, t, JZ7.3 Hz, ArH), 6.63
(1H, d, JZ7.6 Hz, ArH), 4.56 (2H, s, CH2OAc), 2.92 (2H,
dd, JZ8.3, 7.7 Hz, CH2), 2.46 (2H, dd, JZ8.3, 7.7 Hz,
CH2), 2.04 (3H, s, OAc); 13C NMR d/ppm) 20.9 (CH2), 25.7
(OAc), 27.6 (CH2), 65.5 (CH2OAc), 126.2 (CH), 126.4

2838
S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
(CH), 127.2 (CH), 127.2 (CH), 127.3 (CH), 128.3 (2!CH),
129.9 (2!CH), 131.1 (C), 135.6 (C), 135.8 (C), 137.9 (C),
138.3 (C), 170.9 (OCOCH3); MS (EI) m/z (%): 278 (MC,
55), 266 (20), 234 (22), 220 (29), 219 (100), 218 (62), 217
(62), 216 (75), 215 (76), 205 (42), 204 (55), 203 (95), 202
(92), 191 (40), 189 (41), 179 (23), 178 (51), 165 (33), 141
(26), 129 (37), 128 (31), 127 (21), 115 (44), 101 (23), 91
(89), 77 (22), 43 (73); HRMS calculated for C19H18O2 MC
278.1307, found 278.1307.
(OCOCH3); MS (EI) m/z (%): 389 (MC1, 29), 388 (MC,
100), 329 (32), 328 (71), 327 (23), 298 (25), 297 (54), 239
(24), 141 (19); HRMS calculated for C25H24O4 MC
388.1675, found 388.1675.
3.1.29. (6,7-Dimethoxy-1-phenyl-3,4-dihydronaphtha-
len-2-yl)methyl acetate 19c. Similarly alcohol 18c
(0.15 g, 0.58 mmol) gave acetate 19c as a yellow solid
(0.17 g, 88%). MpZ106 8C; IR nmax (cmK1); 1732 (s, C]O
1
stretch), 1605, 1573 (m, C]C stretch); H NMR d/ppm
3.1.26. [1-(o-Tolyl)-3,4-dihydronaphthalen-2-yl]methyl
acetate 13d. Similarly alcohol 12d (0.20 g, 0.80 mmol)
gave acetate 13d as a light brown oil (0.22 g, 94%). IR nmax
(cmK1) 1725 (s, C]O stretch), 1605, 1575 (m, C]C
stretch); 1H NMR d/ppm 7.27–7.01 (7H, m, 7!ArH), 6.52
(1H, d, JZ7.6 Hz, ArH), 4.50 (1H, d, JZ14.4 Hz, one of
CH2OAc), 4.43 (1H, d, JZ14.4 Hz, one of CH2OAc), 2.93
(2H, dd, JZ8.4, 7.7 Hz, CH2), 2.47 (2H, dd, JZ8.4, 7.5 Hz,
CH2), 2.06 (3H, s, ArCH3)a, 2.03 (3H, s, OCOCH3)a,
assignments with the same superscript may be interchanged;
13C NMR d/ppm 19.4 (ArCH3), 20.9 (CH2), 25.1 (OAc),
28.1 (CH2), 65.4 (CH2OAc), 125.6 (CH), 125.8 (CH), 126.4
(CH), 127.1 (CH), 127.2 (CH), 127.7 (CH), 130.0 (2!CH),
131.0 (C), 135.0 (C), 135.4 (C), 136.7 (C), 137.2 (C), 137.4
(C), 170.9 (OCOCH3); MS (EI) m/z (%): 292 (MC, 10), 232
(24), 217 (100), 105 (6), 91 (5), 43 (9); HRMS calculated for
C20H20O2 MC 292.1463, found 292.1425.
7.43–7.34 (3H, m, 3!ArH), 7.19–7.16 (2H, m, 2!ArH),
6.72 (1H, s, ArH), 6.20 (1H, s, ArH), 4.54 (2H, s, CH2OAc),
3.89 (3H, s, OCH3) 3.56 (3H, s, OCH3), 2.85 (2H, dd, JZ
8.5, 7.6 Hz, CH2), 2.44 (2H, dd, JZ8.4, 7.7 Hz, CH2), 2.04
(3H, s, OAc); 13C NMR d/ppm 20.9 (CH2), 25.7 (CH2), 27.7
(CH3), 55.8 (OCH3), 55.9 (OCH3), 65.6 (CH2OH), 110.8
(CH), 110.9 (CH), 127.3 (CH), 128.2 (2!CH), 128.5 (C),
128.8 (C), 129.8 (2!CH), 137.9 (C), 138.1 (C), 146.9 (C),
148.0 (2!C), 171.1 (OCOCH3), (one quaternary carbon
missing); MS (EI) m/z (%): 339 (MC1, 31), 338 (MC, 100),
336 (36), 279 (71), 278 (95), 277 (53), 248 (41), 247 (64),
245 (32), 203 (27), 189 (24), 165 (21), 91 (21), 43 (66);
HRMS calculated for C21H22O4 MC 338.1518, found
338.1519.
3.1.30. [6,7-Dimethoxy-1-(o-tolyl)-3,4-dihydronaphtha-
len-2-yl]methyl acetate 19d. In a similar manner as
described above alcohol 18d (0.28 g, 0.90 mmol) afforded
acetate 19d as cream white semi-solid (0.28 g, 88%). IR
nmax (cmK1); 1731 (s, C]O stretch), 1605, 1510 (s, C]C
stretch); 1H NMR d/ppm 7.26–7.21 (3H, m, 3!ArH), 7.07
(1H, d, JZ6.6 Hz, ArH), 6.73 (1H, s, ArH), 6.08 (1H, s,
ArH), 4.48 (1H, d, JZ12.1 Hz, one of CH2OAc), 4.42 (1H,
d, JZ12.1 Hz, one of CH2OAc), 3.88 (3H, s, OCH3), 3.54
(3H, s, OCH3), 2.90–2.84 (2H, m, CH2), 2.45 (2H, dd, JZ
8.7, 7.4 Hz, CH2), 2.06 (3H, s, OAc)a, 2.03 (3H, s, ArCH3)a,
assignments with the same superscript may be interchanged;
13C NMR d/ppm 19.3 (ArCH3), 20.9 (CH2), 25.4 (OAc),
27.8 (CH2), 55.9 (2!OCH3), 65.5 (CH2OAc), 109.9 (CH),
110.9 (CH), 125.8 (CH), 127.6 (CH), 127.9 (C), 128.4 (C),
128.7 (C), 129.9 (CH), 130.0 (CH), 136.6 (C), 137.1 (C),
137.3 (C), 147.2 (C), 148.1 (C), 171.1 (OCOCH3); 13C
NMR d/ppm 20.1 (CH2), 27.7 (CH2), 125.1 (CH), 125.9
(CH), 126.3 (CH), 126.76 (CH), 126.79 (CH), 127.9 (CH),
128.1 (CH), 128.39 (CH), 128.4 (CH), 128.9 (CH), 130.2
(CH), 132.6 (C), 132.9 (C), 133.5 (C), 135.0 (C), 135.8 (C),
138.1 (C), 153.0 (C), 193.0 (CHO); MS (EI) m/z (%): 353
(MC1, 24), 352 (MC, 40), 351 (10), 292 (53), 277 (100),
245 (33), 201 (27), 115 (27), 43 (44); HRMS calculated for
C22H24O4 MC 352.1675, found 352.1766.
3.1.27. [6,7-Dimethoxy-1-(3,4,5-trimethoxyphenyl)-3,4-
dihydronaphthalen-2-yl]methyl acetate 19a. Using the
same procedure as outlined above alcohol 18a (0.37 g,
0.96 mmol) afforded acetate 19a as light yellow oil (0.33 g,
80%). IR nmax (cmK1) 1731 (s, C]O stretch), 1583 (s,
C]C stretch); 1H NMR d/ppm 6.73 (1H, s, ArH), 6.42 (2H,
s, 20 and 60-H), 6.32 (1H, s, ArH), 4.60 (2H, s, CH2OAc),
3.90 (3H, s, OCH3), 3.89 (3H, s, OCH3), 3.82 (6H, s, 2!
OCH3), 3.62 (3H, s, OCH3), 2.85 (2H, dd, JZ8.4, 7.6 Hz,
CH2), 2.44 (2H, dd, JZ8.4, 7.8 Hz, CH2), 2.07 (3H, s,
OAc); 13C NMR d/ppm 20.9 (CH2), 25.8 (OAc), 27.7 (CH2),
55.8 (OCH3), 55.9 (OCH3), 56.1 (2!OCH3), 60.9 (OCH3),
65.8 (CH2OAc), 106.9 (20 and 60-C), 110.8 (CH), 110.9
(CH), 128.2 (C), 128.5 (C), 128.7 (C), 133.5 (C), 137.0 (C),
138.1 (C), 147.0 (C), 148.2 (C), 153.1 (2!C), 171.0
(OCOCH3); MS (EI) m/z (%): 352 (MC, 54), 188 (28), 87
(14), 57 (77), 43 (100); HRMS calculated for C22H24O4 MC
352.1675, found 352.1743.
3.1.28. [6,7-Dimethoxy-1-(1-naphthyl)-3,4-dihydro-
naphthalen-2-yl]methyl acetate 19b. Similarly alcohol
18b (0.17 g, 0.49 mmol) afforded acetate 19b as yellow
semi-solid (0.17 g, 89%). IR nmax (cmK1) 1730 (s, C]O
stretch), 1605 (m, C]C stretch); 1H NMR d/ppm 7.88–7.84
(2H, m, 2!ArH), 7.65 (1H, d, JZ8.4 Hz, ArH), 7.54–7.42
(2H, m, 2!ArH), 7.37–7.31 (2H, m, 2!ArH), 6.77 (1H, s,
ArH), 5.99 (1H, s, ArH), 4.43 (1H, d, JZ12.2 Hz, one of
CH2OAc), 4.38 (1H, d, JZ12.2 Hz, one of CH2OAc), 3.87
(3H, s, OCH3), 3.33 (3H, s, OCH3), 2.97–2.89 (2H, m, CH2),
2.59–2.53 (2H, m, CH2), 1.95 (3H, s, OAc); 13C NMR d/
ppm 20.8 (CH2), 25.7 (OAc), 27.9 (CH2), 55.8 (OCH3), 55.9
(OCH3), 65.6 (CH2OAc), 110.6 (CH), 110.9 (CH), 125.4
(CH), 125.8 (2!CH), 126.0 (CH), 127.4 (CH), 127.9 (CH),
128.1 (C), 128.2 (CH), 128.5 (C), 130.5 (C), 132.3 (C),
133.6 (C), 135.5 (C), 135.9 (C), 147.0 (C), 148.1 (C), 170.9
3.1.31. [1-(3,4,5-Trimethoxyphenyl)naphthalen-2-yl]-
methyl acetate 14a. To a solution of acetate 13a (0.50 g,
1.46 mmol) in dry CH2Cl2 (30 mL) was added DDQ
(0.85 g, 1.98 mmol) and the mixture immediately turned
green. The reaction mixture was then refluxed under
nitrogen for 16 h over which time it turned pale green.
After allowing to cool to room temperature, the mixture was
poured into an aqueous solution of 5% NaHCO3 (50 mL)
and extracted with CH2Cl2 (3!100 mL). The organic
extracts were combined, washed with brine (20 mL), dried
(MgSO4), filtered through Celite plug and the excess solvent
removed in vacuo. The resultant oil was purified by column

S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
2839
chromatography using 30% ethyl acetate as eluent to obtain
the substituted naphthalene 14a as an orange solid (0.39 g,
78%). MpZ85–87 8C; IR nmax (cmK1) 1734 (s, C]O
stretch), 1582 (s, C]C stretch); 1H NMR d/ppm 7.89–7.85
(2H, m, 2!ArH), 7.60–7.54 (2H, m, 2!ArH), 7.51–7.38
(2H, m, 2!ArH), 6.55 (2H, s, 20 and 60-H), 5.07 (2H, s,
CH2OAc), 3.96 (3H, s, OCH3), 3.82 (6H, s, 2!OCH3), 2.07
(3H, s, OAc); 13C NMR d/ppm 20.9 (OAc), 56.0
(2!OCH3), 60.9 (OCH3), 64.7 (CH2OAc), 107.3 (20 and
60-C), 126.0 (2!CH), 126.2 (CH), 126.7 (CH), 127.7 (CH),
127.9 (CH), 130.8 (C), 132.6 (C), 133.0 (C), 133.2 (C),
137.3 (C), 139.3 (C), 153.0 (2!C), 170.6 (OCOCH3); MS
(EI) m/z (%): 367 (MC1, 66), 366 (MC, 100), 320 (39), 305
(48), 291 (33), 277 (29), 276 (28), 275 (24), 189 (23), 43
(29); HRMS calculated for C22H22O5 MC 366.1467, found
366.1468.
(3H, s, OAc)a; 13C NMR d/ppm 19.9 (ArCH3)a, 20.7
(OCOCH3)a, 64.7 (CH2OAc), 125.8 (CH), 126.0 (CH),
126.1 (CH), 126.1 (CH), 126.3 (CH), 127.7 (CH), 127.8
(CH), 127.9 (CH), 129.9 (CH), 130.0 (CH), 130.7 (C), 132.2
(C), 133.1 (C), 136.9 (C), 137.1 (C), 138.7 (C), 170.9
(OCOCH3), assignments with the same superscript may be
interchanged; MS (EI) m/z (%): 291 (MC1, 30), 290 (MC,
85), 231 (80), 229 (89), 216 (75), 215 (100), 202 (50), 189
(22), 149 (31), 43 (71); HRMS calculated for C20H18O2 MC
290.1307, found 290.1307.
3.1.35. [6,7-Dimethoxy-1-(3,4,5-trimethoxyphenyl)-
naphthalen-2-yl]methyl acetate 20a. Using DDQ (0.48 g,
2.10 mmol) in CH2Cl2 (30 mL) according to the same
procedure as outlined above acetate 19a (0.30 g,
0.70 mmol) gave the naphthalene 20a as yellow crystalline
solid (0.22 g, 74%). MpZ150–152 8C; IR nmax (cmK1
)
1
3.1.32. [1-(1-Naphthyl)naphthalen-2-yl]methyl acetate
14b. In a similar manner as described above DDQ (0.21 g,
0.91 mmol) was used to convert acetate 13b (0.20 g,
0.61 mmol) into 14b, obtained as a light yellow oil
(0.19 g, 95%). IR nmax (cmK1) 1738 (s, C]O stretch),
1736 (s, C]O stretch), 1625, 1583 (s, C]C stretch); H
NMR d/ppm 7.64 (1H, d, JZ8.4 Hz, ArH), 7.36 (1H, d,
JZ8.4 Hz, ArH),07.08 (1H, s, ArH), 6.76 (1H, s, ArH), 6.48
(2H, s, 20 and 6 -H), 4.94 (2H, s, CH2OH), 3.93 (3H, s,
OCH3), 3.88 (3H, s, OCH3), 3.76 (6H, s, 2!OCH3), 3.67
(3H, s, OCH3), 1.98 (3H, s, OAc); 13C NMR d/ppm 20.9
(OAc), 55.7 (OCH3), 55.8 (OCH3), 56.1 (2!OCH3), 60.9
(OCH3), 64.9 (CH2OAc), 105.4 (CH), 106.2 (CH), 107.2
(2!CH), 124.8 (CH), 126.2 (CH), 128.2 (C), 129.1 (C),
129.2 (C), 133.6 (C), 137.2 (C), 138.1 (C), 149.5 (C), 149.6
(C), 153.1 (2!C), 170.6 (OCOCH3); MS (EI) m/z (%): 427
(MC1, 19), 426 (MC, 70), 81 (18), 69 (41), 57 (29), 55 (23),
43 (27), 41 (21), 31 (23), 28 (100); HRMS calculated for
C24H26O7 MC 426.1679, found 426.1678.
1
1593, 1587 (m, C]C stretch); H NMR d/ppm 7.98–7.89
(4H, m, 4!ArH), 7.67–7.58 (2H, m, 2!ArH), 7.47–7.39
(3H, m, 3!ArH), 7.24–7.16 (4H, m, 4!ArH), 4.93 (1H, d,
JZ12.5 Hz, one of CH2OAc), 4.84 (1H, d, JZ12.5 Hz, one
of CH2OAc), 1.84 (3H, s, OAc); 13C NMR d/ppm 20.6
(OAc), 64.7 (CH2OAc), 125.4 (CH), 125.9 (CH), 126.1
(2!CH), 126.2 (CH), 126.3 (CH), 126.4 (CH), 126.8 (CH),
127.8 (CH), 127.9 (CH), 128.1 (CH), 128.2 (CH), 128.2
(CH), 132.0 (C), 132.8 (C), 133.1 (C), 133.2 (C), 133.6 (C),
135.4 (C), 137.4 (C), 171.0 (OCOCH3); MS (EI) m/z (%):
327 (MC1, 51), 326 (MC, 97), 284 (21), 268 (20), 267 (60),
266 (85), 265 (100), 263 (27), 262 (43), 253 (40), 251 (64),
249 (21), 238 (23), 43 (19); HRMS calculated for C23H18O2
MC 326.1307, found 326.1307.
3.1.36. [6,7-Dimethoxy-1-(1-naphthyl)naphthalen-2-
yl]methyl acetate 20b. Similarly acetate 19b (0.22 g,
0.57 mmol) gave the substituted arylnaphthalene 20b, as a
yellow solid (0.17 g, 78%) using DDQ (0.13 g, 0.57 mmol)
in CH2Cl2 (15 mL). MpZ110–114 8C; IR nmax (cmK1
)
3.1.33. (1-Phenylnaphthalen-2-yl)methyl acetate 14c.
Similarly acetate 13c (0.14 g, 0.50 mmol) afforded the
arylnaphthalene 14c as light yellow oil (0.13 g, 93%) using
DDQ (0.17 g, 0.75 mmol) in CH2Cl2 (15 mL). IR nmax
(cmK1) 1738 (s, C]O stretch), 1597 (m, C]C stretch); 1H
NMR d/ppm 7.88–7.83 (2H, m, 2!ArH), 7.57 (1H, d,
JZ8.5 Hz, ArH), 7.47–7.43 (5H, m, 5!ArH), 7.30–7.15
(3H, m, 3!ArH), 5.00 (2H, s, CH2OAc), 2.02 (3H, s, OAc);
13C NMR d/ppm) 20.9 (CH3), 64.7 (CH2OH), 125.9 (CH),
126.1 (CH), 126.2 (CH), 126.7 (CH), 127.6 (CH), 127.7
(CH), 127.8 (CH), 128.2 (2!CH), 130.2 (2!CH), 130.8
(C), 132.7 (C), 133.1 (C), 137.8 (C), 139.5 (C), 170.6
(OCOCH3); MS (EI) m/z (%): 277 (MC1, 24), 276 (MC,
100), 234 (23), 215 (78), 202 (34); HRMS calculated for
C19H16O2 MC 276.1150, found 276.1113.
1736 (s, C]O stretch), 1624 (m, C]C stretch); 1H NMR d/
ppm 7.85 (2H, t, JZ7.8 Hz, 2!ArH), 7.72 (1H, d,
JZ8.4 Hz, ArH), 7.53–7.32 (4H, m, 4!ArH), 7.18–7.14
(2H, m, 2!ArH), 7.11 (1H, s, ArH), 6.35 (1H, s, ArH), 4.82
(1H, d, JZ12.3 Hz, one of CH2OAc), 4.69 (1H, d,
JZ12.3 Hz, one of CH2OAc), 3.91 (3H, s, OCH3), 3.36
(3H, s, OCH3), 1.72 (3H, s, OAc); 13C NMR d/ppm 20.6
(OAc), 55.4 (OCH3), 55.8 (OCH3), 64.9 (CH2OAc), 105.5
(CH), 106.2 (CH), 124.9 (CH), 125.4 (CH), 125.9 (CH),
126.0 (2!CH), 126.4 (CH), 127.8 (CH), 128.2 (CH), 128.2
(CH), 128.8 (C), 129.2 (C), 130.3 (C), 132.6 (C), 133.6 (C),
135.7 (C), 136.1 (C), 149.6 (C), 149.7 (C), 170.5
(OCOCH3); MS (EI) m/z (%): 387 (MC1, 25), 386 (MC,
100), 385 (26), 384 (90), 372 (32), 371 (22), 370 (27), 368
(19), 344 (20), 343 (27), 149 (25); HRMS calculated for
C25H22O4 MC 386.1518, found 386.1519.
3.1.34. [1-(o-Tolyl)naphthalen-2-yl]methyl acetate 14d.
Similarly using DDQ (0.46 g, 1.53 mmol) in CH2Cl2
(30 mL) acetate 13d (0.20 g, 0.51 mmol) afforded the
substituted naphthalene 14d as a light brown crystalline
solid (0.20 g, 100%). MpZ86–90 8C; IR nmax (cmK1) 1736
(s, C]O stretch); 1H NMR d/ppm 7.88–7.83 (2H, m,
2!ArH), 7.58 (1H, d, JZ8.5 Hz, ArH), 7.46–7.41 (1H, m,
ArH), 7.35–7.27 (5H, m, 5!ArH), 7.13 (1H, d, JZ7.5 Hz,
ArH), 4.97 (1H, d, JZ12.4 Hz, one of CH2OAc), 4.95 (1H,
d, JZ12.4 Hz, one of CH2OAc), 2.00 (3H, s, ArCH3)a, 1.91
3.1.37. (6,7-Dimethoxy-1-phenylnaphthalen-2-yl)methyl
acetate 20c. Similarly dihydronaphthalene 19c (0.17 g,
0.56 mmol) gave the substituted naphthalene 20c as a
yellow crystalline solid (0.17 g, 100%) using DDQ (0.38 g,
1.66 mmol) in CH2Cl2 (20 mL). MpZ75–78 8C; IR nmax
(cmK1) 1736 (s, C]O stretch), 1624 (m, C]C stretch); 1H
NMR d/ppm 7.62 (1H, d, JZ8.4 Hz, ArH), 7.36–7.33 (4H,
m, 4!ArH), 7.23–7.19 (2H, m, 2!ArH), 7.06 (1H, s, ArH),
6.63 (1H, s, ArH), 4.87 (2H, s, CH2OAc), 3.90 (3H, s,

2840
S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
OCH3) 3.59 (3H, s, OCH3), 1.93 (3H, s, OAc); 13C NMR d/
ppm 20.9 (OAc), 55.4 (OCH3), 55.8 (OCH3), 64.9
(CH2OAc), 105.4 (CH), 106.1 (CH), 124.9 (CH), 126.1
(CH), 127.5 (CH), 128.3 (2!CH), 129.1 (C), 129.1 (C),
129.9 (2!CH), 138.1 (C), 138.3 (C), 149.4 (C), 149.5 (C),
170.6 (OCOCH3), (one quaternary carbon missing); MS
(EI) m/z (%): 337 (MC1, 59), 336 (MC, 100), 265 (19), 246
(37), 245 (56), 215 (24), 203 (26), 202 (33), 191 (22), 189
(40), 43 (42); HRMS calculated for C21H20O4 MC
336.1362, found 336.1362.
(0.40 g, 1.39 mmol) into 21b, a brown crystalline solid
(0.31 g, 79%). MpZ116–119 8C; IR nmax (cmK1) 3386
(s, broad, OH stretch), 1592, 1568 (m, C]C stretch); H
1
NMR d/ppm 7.89–7.79 (4H, m, 4!ArH), 7.67 (1H, d, JZ
8.5 Hz, ArH), 7.51–7.46 (1H, m, ArH), 7.38–7.28 (3H, m,
3!ArH), 7.17–7.06 (4H, m, 4!ArH), 4.32 (1H, d, JZ
13.0 Hz, one of CH2OH), 4.27 (1H, d, JZ13.0 Hz, one of
CH2OH); 13C NMR d/ppm 63.3 (CH2OH), 125.4 (CH),
125.7 (2!CH), 125.8 (CH), 126.0 (CH), 126.1 (CH), 126.4
(CH), 126.9 (CH), 127.8 (CH), 127.9 (CH), 128.1 (CH),
128.3 (2!CH), 132.7 (C), 132.8 (C), 133.0 (C), 133.6 (C),
135.5 (C), 135.7 (C), 136.7 (C); MS (EI) m/z (%): 285 (MC
1, 23), 284 (MC, 100), 265 (32), 128 (18); HRMS calculated
for C21H16O MC 284.1201, found 284.1202.
3.1.38. [6,7-Dimethoxy-1-(o-tolyl)naphthalen-2-yl]-
methyl acetate 20d. In a similar manner as described
above dihydronaphthalene 19d (0.31 g, 0.88 mmol) was
converted into naphthalene 20d, which was obtained as a
yellow solid (0.24 g, 78%) using DDQ (0.20 g, 0.88 mmol)
in CH2Cl2 (20 mL). MpZ91–93 8C; IR nmax (cmK1) 1736
(s, C]O stretch), 1624 (m, C]C stretch); 1H NMR d/ppm
7.73 (1H, d, JZ8.4 Hz, ArH), 7.45 (1H, d, JZ8.4 Hz, ArH),
7.36–7.25 (3H, m, 3!ArH), 7.16 (1H, s, ArH), 7.16–7.14
(1H, s, ArH), 6.53 (1H, s, ArH), 4.93 (1H, d, JZ12.2 Hz,
one of CH2OAc), 4.87 (1H, d, JZ12.2 Hz, one of
CH2OAc), 4.00 (3H, s, OCH3), 3.67 (3H, s, OCH3), 2.00
(3H, s, ArCH3), 1.94 (3H, s, OCOCH3); 13C NMR d/ppm
19.5 (ArCH3), 20.8 (OCOCH3), 55.5 (OCH3), 55.8 (OCH3),
64.9 (CH2OAc), 104.8 (CH), 106.3 (CH), 124.9 (CH), 125.9
(CH), 126.0 (CH), 127.9 (CH), 129.0 (C), 129.1 (C), 129.9
(2!CH), 136.8 (C), 137.5 (C), 137.6 (C), 149.6 (C), 149.7
(C), 170.7 (OCOCH3), (one quaternary carbon missing);
MS (EI) m/z (%): 351 (MC1, 44), 350 (MC, 100), 291 (26),
290 (28), 276 (15), 275 (19), 260 (17), 259 (46), 202 (17),
189 (16), 43 (18); HRMS calculated for C22H22O4 MC
350.1518, found 350.1517.
3.1.41. (1-Phenylnaphthalen-2-yl)methanol 21c. Simi-
larly dihydronaphthyl alcohol 12c (0.26 g, 1.10 mmol)
afforded naphthalene 21c as a light yellow oil (0.20 g,
78%) using DDQ (0.25 g, 1.10 mmol) in CH2Cl2 (25 mL).
IR nmax (cmK1) 3420 (m, broad, OH stretch), 1596 (s, C]C
stretch); 1H NMR d/ppm 7.89 (1H, d, JZ8.4 Hz, ArH), 7.87
(1H, d, JZ8.4 Hz, ArH), 7.68 (1H, d, JZ8.5 Hz, ArH),
7.49–7.41 (5H, m, 5!ArH), 7.37–7.34 (3H, m, 3!ArH),
4.56 (2H, s, CH2OH); 13C NMR d/ppm 63.3 (CH2OH),
125.6 (CH), 125.7 (CH), 125.9 (CH), 126.5 (CH), 127.4
(CH), 127.7 (CH), 127.9 (CH), 128.3 (2!CH), 130.0 (2!
CH), 132.6 (C), 132.8 (C), 135.5 (C), 137.8 (C), 138.1 (C);
MS (EI) m/z (%): 235 (MC1, 28), 234 (MC, 100), 215 (50),
205 (46), 202 (35), 157 (14), 129 (22), 108 (16); HRMS
calculated for C17H14O MC 234.1045, found 234.1046.
3.1.42. 1-Bromonaphthalene-2-carbaldehyde 22. 1-
Bromo-3,4-dihydronaphthalene-2-carbaldehyde (0.45 g,
1.898 mmol), selenium powder (0.30 g, 5.694 mmol) and
dimethyl sulfoxide (0.5 mL) were slowly heated to 170 8C.
The reaction mixture was heated at the same temperature for
5 min where sputtering took place. After sputtering had
ceased, the mixture was allowed to cool to room
temperature before being filtered and washed with an
excess amount of CH2Cl2. The excess solvent was removed
on a rotary evaporator to obtain a black oil that was purified
by column chromatography using 5% ethyl acetate/hexane
as eluant to give the desired product 22 as a bright yellow
3.1.39. [1-(3,4,5-Trimethoxyphenyl)naphthalen-2-yl]-
methanol 21a. To a solution of dihydronaphthalenylmetha-
nol 12a (0.11 g, 0.34 mmol) in CH2Cl2 (15 mL) was added
DDQ and a green solution resulted. The resultant mixture
was refluxed for 16 h after which time it turned dark brown.
The mixture was then allowed to cool to room temperature
before being neutralized with 5% NaHCO3 (10 mL) and
being extracted with CH2Cl2 (3!50 mL). The organic
extracts were combined, washed with brine and concen-
trated under reduced pressure to give a brown oil. The oil
was purified by column chromatography using 30%
ethylacetate/hexane as an eluent to give 21a as a yellow
solid (0.09 g, 82%). MpZ90–91 8C; IR nmax (cmK1) 3488
solid (0.31 g, 69%). MpZ106–108 8C; IR nmax (cmK1
)
1
1687 (s, C]O stretch), 1619, 1597 (s, C]C stretch); H
NMR d/ppm 10.67 (1H, s, CHO), 8.53–8.50 (1H, m, ArH),
7.95–7.84 (3H, m, 3!ArH), 7.72–7.67 (2H, m, 2!ArH);
13C NMR d/ppm 124.1 (CH), 128.1 (CH), 128.2 (CH), 128.3
(CH), 128.4 (CH), 128.5 (C), 129.7 (CH), 131.1 (C), 132.1
(C), 137.2 (C), 192.8 (CHO); MS (EI) m/z (%): 235
(MC81Br, 99), 233 (MC79Br, 100), 206 (28), 127 (35), 126
(89), 63 (15); HRMS calculated for C11H7O79Br MC
233.9680, found 233.9708.
1
(s, broad, OH stretch), 1582 (s, C]C stretch); H NMR d/
ppm 7.90 (1H, d, JZ8.4 Hz, ArH), 7.87 (1H, d, JZ8.5 Hz,
ArH), 7.69 (1H, d, JZ8.5 Hz, ArH), 7.54 (1H, d,0JZ8.3 Hz,
ArH), 7.49–7.37 (2H, m, 2!ArH), 6.53 (2H, s, 2 and 60-H),
4.61 (2H, s, CH2OH), 3.95 (3H, s, OCH3), 3.81 (6H, s,
2!OCH3); 13C NMR d/ppm 56.1 (2!OCH3), 60.9
(OCH3), 63.4 (CH2OH), 107.2 (2!CH), 125.7 (2!CH),
126.1 (CH), 126.6 (CH), 127.8 (CH), 128.0 (CH), 132.6 (C),
132.8 (C), 133.6 (C), 135.6 (C), 137.1 (C), 137.9 (C), 153.0
(2!C); MS (EI) m/z (%): 325 (MC1, 10), 324 (MC, 100),
219 (9), 165 (7), 18 (7); HRMS calculated for C20H20O4
MC 324.1361, found 324.1351.
3.1.43. 6-Methoxy-1-bromo-3,4-dihydronaphthalene-2-
carbaldehyde 23. Dry DMF (8.0 mL, 102.1 mmol) in dry
CH2Cl2 (60.0 mL) was cooled to 0 8C and phosphorus
tribromide (8.4 mL, 88.52 mmol) was added drop-wise. The
mixture was stirred at 0 8C for 1 h and a cream white
suspension formed. A solution of 6,7-dimethoxy-a-tetralone
(6.00 g, 34.05 mmol) in dry CH2Cl2 (50 mL) was added and
the mixture was heated under reflux for 16 h. After cooling
to 0 8C, aqueous NaHCO3 was added slowly until the
3.1.40. [1-(1-Naphthylnaphthalen-2-yl]methanol 21b. In
a similar manner to that described above DDQ (0.48 g,
2.09 mmol) was used to convert dihydronaphthalene 12b

S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
2841
effervescence had subsided. Extraction of the organic
material into CH2Cl2 (3!100 mL) was followed by drying
the organic layer (MgSO4). The solution was filtered
through a Celite plug and evaporation of the excess solvent
resulted into brown oil. Column chromatography eluting
with 30% ethyl acetate/hexane gave the product 23 as a
(OCH3), 108.2 (2!CH), 121.9 (CH), 123.5 (C), 126.9 (CH),
127.6 (CH), 128.1 (CH), 128.3 (CH), 128.7 (CH), 130.6 (C),
131.1(C), 132.4(C),136.0(C), 146.3(C), 152.9(2!C), 192.7
(CHO);MS(EI)m/z(%):323 (MC1, 22), 322 (MC, 100), 279
(63), 219 (15), 165 (24); HRMS calculated for C20H18O4 MC
322.1205, found 322.1186.
yellow solid (7.79 g, 86%). MpZ61–62 8C; IR nmax (cmK1
)
1659 (s, C]O stretch), 1606, 1586, 1552 (s, C]C stretch);
1H NMR d/ppm 10.20 (1H, s, CHO), 7.83 (1H, d, JZ8.7 Hz,
8-H), 6.82 (1H, dd, JZ8.7, 2.6 Hz, 7-H), 6.72 (1H, d,
JZ2.5 Hz, 5-H), 3.86 (3H, s, OMe), 2.80 (2H, dd, JZ8.4,
7.2 Hz, CH2), 2.60 (2H, dd, JZ8.7, 6.0 Hz, CH2); 13C NMR
d/ppm 22.7 (CH2), 27.7 (CH2), 55.4 (OCH3), 112.1 (CH),
113.3 (CH), 125.9 (C), 130.7 (CH), 132.1 (C), 139.0 (C),
141.2 (C), 162.0 (C), 192.9 (CHO); MS (EI) m/z (%): 267
(MC81Br, 80), 265 (MC79Br, 83), 236 (28), 187 (46), 159
(97), 158 (100), 144 (59), 128 (41), 115 (81); HRMS
calculated for C12H11O279Br MC 265.9942, found 265.9936.
3.1.46. 1-(1-Naphthyl)-naphthalene-2-carbaldehyde 25b.
Using the same procedure as described above, 22 (0.30 g,
1.276 mmol) was reacted with 1-naphthylboronic acid 10b
(0.31 g, 1.914 mmol) under Suzuki coupling conditions to
give 25b as a yellow crystalline solid (0.32 g, 89%). MpZ
112–114 8C; IR nmax (cmK1) 1687 (s, C]O stretch), 1619
1
and 1593 (m, C]C stretch); H NMR d/ppm 9.68 (1H, s,
CHO), 8.15 (1H, d, JZ8.6 Hz, ArH), 8.02–7.92 (4H, m, 4!
ArH), 7.62–7.54 (2H, m, 2!ArH), 7.49–7.44 (2H, m,
2!ArH), 7.36 (1H, d, JZ8.1 Hz, ArH), 7.31–7.25 (2H, m,
2!ArH), 7.20 (1H, d, JZ8.4 Hz, ArH); 13C NMR d/ppm
122.1 (CH), 125.0 (CH), 126.2 (CH), 126.3 (CH), 126.8
(CH), 126.9 (CH), 127.7 (CH), 128.2 (CH), 128.3 (CH),
128.6 (CH), 128.8 (CH), 128.9 (CH), 129.1 (CH), 132.1 (C),
132.9 (C), 133.0 (C), 133.3 (C), 133.5 (C), 136.1 (C), 144.8
(C), 192.4 (CHO); MS (EI) m/z (%): 283 (MC1, 23), 282
(MC, 100), 281 (81), 265 (26), 253 (86), 252 (97), 126 (35),
113 (15); HRMS calculated for C21H14O MC 282.1045,
found 282.1035.
3.1.44. 6-Methoxy-1-bromonaphthalene-2-carbaldehyde
24. Using the same procedure as described above,
6-methoxy-1-bromo-3,4-dihydronaphthalene-2-carbal-
dehyde 23 (3.98 g, 14.90 mmol) was converted into
7-methoxy-1-bromonaphthalene-2-carbaldehyde 24 in the
presence of selenium powder (2.30 g, 29.80 mmol) and
dimethyl sulfoxide (2 mL). The product was obtained as a
light brown solid (2.85 g, 72%). MpZ123–126 8C; IR nmax
1
(cmK1) 1682 (s, C]O stretch), 1620 (s, C]C stretch); H
NMR d/ppm 10.58 (1H, s, CHO), 8.36 (1H, d, JZ9.4 Hz,
8-H), 7.87 (1H, d, JZ8.7 Hz, 3- or 4-H), 7.68 (1H, d,
JZ8.7 Hz, 3- or 4-H), 7.28 (1H, dd, JZ9.4, 2.5 Hz, 7-H),
7.11 (1H, d, JZ2.5 Hz, 5-H), 3.96 (3H, s, OMe); 13C NMR
d/ppm 55.6 (OCH3), 106.4 (CH), 120.7 (CH), 124.7 (CH),
126.9 (CH) 127.2 (C), 129.4 (C), 129.8 (CH), 130.4 (C),
139.0 (C), 160.6 (C), 192.5 (CHO); MS (EI) m/z (%): 265
(MC81Br, 47), 263 (MC79Br, 46), 261 (100), 202 (17), 156
(16), 113 (22), 73 (17); HRMS calculated for C12H9O729Br
MC 263.9786, found 263.9750.
3.1.47. 1-Phenylnaphthalene-2-carbaldehyde 25c. Sub-
stituted naphthalene 25c was obtained as a light yellow oil
(0.26 g, 87%) from the Suzuki coupling of bromonaphtha-
lene carbaldehyde 22 (0.30 g, 1.276 mmol) and 1-phenyl-
boronic acid (0.22 g, 1.914 mmol) using the same procedure
as outlined above. 1H NMR d/ppm 9.89 (1H, s, CHO), 8.06
(1H, d, JZ8.6 Hz, ArH), 7.92 (2H, d, JZ9.7 Hz, 2!ArH)
7.67–7.58 (2H, m, 2!ArH), 7.52–7.51 (3H, m, 3!ArH),
7.47–7.31 (3H, m, 3!ArH); 13C NMR d/ppm 122.1 (CH),
126.8 (CH), 127.7 (CH), 128.2 (CH), 128.2 (2!CH), 128.3
(CH), 128.4 (CH), 128.7 (CH), 130.9 (2!CH), 131.2 (C),
132.4 (C), 135.2 (C), 136.1 (C), 146.5 (C), 192.6 (CHO);
MS (EI) m/z (%): 233 (MC1, 18), 232 (MC, 100), 202 (64),
101 (18); HRMS calculated for C17H12O MC 232.0888,
found 232.0865.
3.1.45. 1-(3,4,5-Trimethoxyphenyl)-naphthalene-2-car-
baldehyde 25a. To [Pd(PPh3)4] (0.14 g, 0.127 mmol)
was added deoxygenated solutions of 22 (0.30 g,
1.276 mmol) in DME (10 mL) and 3,4,5-trimethoxy-1-
phenylboronic acid 10a (0.38 g, 1.914 mmol) in ethanol
(5 mL). This was followed by a deoxygenated solution of
aqueous sodium carbonate (1.06 g, 10.85 mmol in 5.0 mL
water). The resultant mixture was refluxed under nitrogen
for 46 h over which time it turned deep red. After
allowing to cool to room temperature, the mixture was
quenched with water (10 mL) and the organic material
extracted with CH2Cl2 (3!25 mL). The resultant organic
extracts were combined, dried (MgSO4), filtered through
a Celite plug and the excess solvent removed using a
rotary evaporator. The subsequent oil was purified by
column chromatography using 30% ethyl acetate/hexane
as the eluent to afford the desired product 25a as a
yellow solid (0.40 g, 94%). MpZ89–92 8C; IR nmax
(cmK1) 1694 (s, C]O stretch), 1626, 1597 (s, C]C
3.1.48. 1-(o-Tolyl)naphthalene-2-carbaldehyde 25d.
Using the same procedure as outlined above, tolylnaphtha-
lene carbaldehyde 25d was synthesized as a yellow
crystalline solid (0.29 g, 94%) from the Suzuki coupling
of carbaldehyde 22 (0.30 g, 1.276 mmol) and o-tolylboronic
acid 10d. MpZ60–61 8C; IR nmax (cmK1) 1687 (s, C]O
1
stretch), 1626, 1618, 1596 (s, C]C stretch); H NMR d/
ppm 9.82 (1H, s, CHO), 8.07 (1H, d, JZ8.6 Hz, ArH), 7.93
(2H, d, JZ9.1 Hz, 2!ArH), 7.64–7.59 (1H, m, ArH), 7.48–
7.31 (5H, m, 5!ArH), 7.24 (1H, d, JZ6.6 Hz, ArH), 1.96
(3H, s, ArCH3); 13C NMR d/ppm 20.0 (ArCH3), 122.0 (CH),
125.7 (CH), 126.9 (CH), 127.2 (CH), 128.3 (CH), 128.4
(CH), 128.6 (CH), 128.8 (CH) 130.1 (CH), 130.9 (CH),
131.0 (C), 132.1 (C), 134.8 (C), 136.2 (C), 137.3 (C), 146.3
(C), 192.6 (CHO); MS (EI) m/z (%): 246 (MC, 100), 231
(38), 218 (88), 202 (43), 130 (39), 99 (10), 68 (74);
HRMS calculated for C18H14O MC 246.1045, found
246.1049.
1
stretch); H NMR d/ppm 9.96 (1H, s, CHO), 8.05 (1H, d,
JZ8.6 Hz, ArH), 7.93 (2H, d, JZ8.4 Hz, 2!ArH), 7.76
(1H, d, JZ8.2 Hz, ArH), 7.65–7.61 (1H, m, ArH),
7.52–7.48 (1H, m, ArH), 6.63 (2H, s, 20 and 60-H), 3.85 (9H,
s, 3!OCH3); 13C NMR d/ppm 56.2 (2!OCH3), 60.8

2842
S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
3.1.49. 1-(3,4,5-Trimethoxyphenyl)-6-methoxynaphtha-
lene-2-carbaldehyde 26a. In the same way as outlined
above, 7-methoxy-1-bromonaphthalene 24 (0.30 g,
1.132 mmol) and 3,4,5-trimethoxy-1-phenylboronic acid
10a (0.36 g, 1.697 mmol) were subjected to Suzuki
coupling reaction conditions to give the desired product
26a, as a light yellow crystalline solid (0.32 g, 80%). MpZ
132–134 8C; IR nmax (cmK1) 1690 (s, C]O stretch), 1623,
1599 (s, C]C stretch); 1H NMR d/ppm 9.89 (1H, s, CHO),
8.02 (1H, d, JZ8.6 Hz, 4-H), 7.80 (1H, d, JZ8.6 Hz, 3-H),
7.65 (1H, d, JZ9.2 Hz, 8-H), 7.21 (1H, d, JZ2.5 Hz, 5-H),
7.13 (1H, dd, JZ9.2, 2.5 Hz, 7-H), 6.61 (2H, s, 20 and 60-H),
3.96 (6H, s, 2!OCH3), 3.84 (6H, s, 2!OCH3); 13C NMR
d/ppm 55.4 (OCH3), 56.2 (2!OCH3), 61.0 (OCH3), 106.3
(CH), 108.2 (2!CH), 119.5 (CH), 122.7 (CH), 127.0 (CH),
127.4 (C), 129.3 (CH), 129.5 (C), 130.8 (C), 137.7 (C),
137.9 (C), 146.4 (C), 152.9 (2!C), 159.9 (C), 192.4 (CHO);
MS (EI) m/z (%): 352 (MC, 57), 309 (23), 304 (25), 246
(100), 231 (36), 215 (37), 202 (35), 185 (30), 115 (19);
HRMS calculated for C21H20O5 MC 352.1311, found
352.1341.
3.1.52. 6-Methoxy-1-(o-tolyl)naphthalene-2-carbal-
dehyde 26d. 1-Bromo-7-methoxynaphthalene-2-carbalde-
hyde 24 (0.30 g, 1.132 mmol) and o-tolylboronic 10d
(0.22 g, 1.697 mmol) were coupled in the same manner as
described above to give the desired product 26d, as a light
yellow oil (0.22 g, 71%). IR nmax (cmK1) 1674 (s, C]O
stretch), 1618 (s, C]C stretch); 1H NMR d/ppm 9.74 (1H, s,
CHO), 8.04 (1H, d, JZ8.6 Hz, 4-H), 7.80 (1H, d, JZ8.6 Hz,
3-H), 7.44–7.29 (4H, m, 4!ArH), 7.25–7.21 (2H, m, 2!
ArH), 7.07 (1H, dd, JZ9.2, 2.5 Hz, 7-H), 3.95 (3H, s,
OCH3), 1.96 (3H, s, ArCH3); 13C NMR d/ppm 19.9
(ArCH3), 55.4 (OCH3), 106.4 (CH), 119.4 (CH), 122.8
(CH), 125.6 (CH), 126.9 (CH), 128.5 (CH), 128.9 (CH)
129.3 (C), 130.0 (CH), 130.7 (CH), 130.9 (C), 134.9 (C),
137.2 (C), 138.0 (C), 146.3 (C), 160.0 (C), 192.3 (CHO);
MS (EI) m/z (%): 277 (MC1, 21), 276 (MC, 100), 261 (32),
245 (16), 215 (22), 202 (24); HRMS calculated for
C19H16O2 MC 276.1150, found 276.1156.
3.1.53. [1-(3,4,5-Trimethoxyphenyl)naphthalen-2-yl]-
methanol 21a. To a solution of carbaldehyde 25a (0.17 g,
0.527 mmol) in ethanol (5 mL) was added NaBH4 (0.03 g,
0.659 mmol). The reaction mixture was stirred at room
temperature for 5 min after which time it turned cream
white. The mixture was quenched with water (5 mL) before
being extracted with CH2Cl2 (3!15 mL). The organic
extracts were combined, dried (MgSO4), and then filtered
through a Celite plug and concentrated in vacuo. The
subsequent colourless oil was purified by column chroma-
tography using 30% ethyl acetate/hexane as eluent to afford
21a as light yellow crystalline solid (0.14 g, 82%)
with identical spectroscopic data to that described
previously.
3.1.50. 6-Methoxy-1-(1-naphthyl)naphthalene-2-carbal-
dehyde 26b. Using the same procedure as described above,
bromonaphthalene carbaldehyde 24 (0.30 g, 1.132 mmol)
and 1-naphthylboronic acid 10b (0.29 g, 1.697 mmol) were
coupled to give biaryl 26b, as a yellow solid (0.26 g, 74%).
MpZ181–184 8C; IR nmax (cmK1) 1676 (s, C]O stretch),
1619 (m, C]C stretch); 1H NMR d/ppm 9.61 (1H, s, CHO),
8.12 (1H, d, JZ8.6 Hz, ArH), 8.01 (1H, d, JZ8.3 Hz, ArH),
7.96 (1H, d, JZ8.3 Hz, ArH), 7.89 (1H, d, JZ8.7 Hz, ArH),
7.63–7.58 (1H, m, ArH), 7.50–7.46 (2H, m, 2!ArH), 7.32–
7.19 (4H, m, 4!ArH), 6.96 (1H, dd, JZ9.2, 2.6 Hz, 7-H),
3.93 (3H, s, OCH3); 13C NMR d/ppm 55.4 (OCH3), 106.3
(CH), 119.5 (CH), 122.8 (CH), 124.9 (CH), 126.1 (CH),
126.2 (CH), 126.7 (CH), 127.3 (CH), 128.1 (C), 128.2 (CH),
128.8 (CH), 129.0 (CH), 129.4 (CH), 130.4 (C), 133.0 (C),
133.2 (C), 133.4 (C), 138.0 (C), 144.9 (C), 159.9 (C), 192.2
(CHO); MS (EI) m/z (%): 313 (MC1, 23), 312 (MC, 100),
239 (33), 218 (43), 144 (13), 130 (19), 68 (33);
HRMS calculated for C22H16O2 MC 312.1150, found
312.1174.
3.1.54. [1-(1-Naphthyl)naphthalen-2-yl]methanol 21b. In
the same manner as outlined above, carbaldehyde 25b
(0.30 g, 1.062 mmol) was converted to a biaryl alcohol 21b,
as a brown solid (0.28 g, 93%) using sodium borohydride
(0.05 g, 1.328 mmol) with identical spectroscopic data to
that described previously.
3.1.55. (1-Phenylnaphthalen-2-yl)methanol 21c. Using
sodium borohydride (0.05 g, 1.238 mmol) in the manner
as outlined above, phenylnaphthyl carbaldehyde 25c
(0.23 g, 0.990 mmol) was converted into alcohol 21c, as a
yellow sticky oil (0.21 g, 91%) with identical spectroscopic
data to that described previously.
3.1.51. 6-Methoxy-1-phenylnaphthalene-2-carbaldehyde
26c. In the same manner as detailed above, carbaldehyde
26c was synthesized as a thick yellow oil (0.27 g, 90%)
from the Suzuki coupling of carbaldehyde 24 (0.30 g,
3.1.56. [1-(o-Tolyl)naphthalen-2-yl]methanol 21d. The
desired product 21d, was synthesized as a thick yellow oil
(0.19 g, 95%) from carbaldehyde 25d (0.20 g, 0.812 mmol)
using sodium borohydride (0.04 g, 1.015 mmol) in the same
way as described above. IR nmax (cmK1) 3408 (s, broad, OH
1.132 mmol)
and
phenylboronic
10c
(0.20 g,
1.697 mmol). IR nmax (cmK1) 1681 (s, C]O stretch),
1616, 1573 (s, C]C stretch); H NMR d/ppm 9.81 (1H,
1
s, CHO), 8.04 (1H, d, JZ8.7 Hz, 4-H), 7.79 (1H, d,
JZ8.7 Hz, 3-H) 7.51–7.49 (4H, m, 4!ArH), 7.38–7.35
(2H, m, 2!ArH), 7.21–7.19 (1H, m, ArH), 7.08 (1H, dd,
JZ9.3, 2.6 Hz, 7-H), 6.92–6.83 (1H, m, ArH), 3.93 (3H,
s, OCH3); 13C NMR d/ppm 55.4 (OCH3), 106.3 (CH),
119.3 (CH), 120.3 (C), 122.8 (CH), 127.0 (CH), 127.4
(C), 128.1 (2!CH) 129.3 (CH), 129.5 (CH), 130.8 (2!
CH), 135.2 (C), 137.9 (C), 146.7 (C), 159.9 (C), 192.5
(CHO); MS (EI) m/z (%): 263 (MC1, 33), 262 (MC,
40), 218 (100), 130 (61), 99 (11), 68 (82); HRMS
calculated for C18H14O2 MC 262.0993, found 262.0991.
1
stretch), 1621, 1596, 1572 (s, C]C stretch); H NMR d/
ppm 7.90 (1H, d, JZ8.4 Hz, ArH), 7.87 (1H, d, JZ7.5 Hz,
ArH), 7.70 (1H, d, JZ8.4 Hz, ArH), 7.48–7.43 (1H, m,
ArH), 7.35–7.24 (5H, m, 5!ArH), 7.14 (1H, d, JZ7.3 Hz,
ArH), 4.48 (2H, s, CH2OH), 1.91 (3H, s, ArCH3); 13C NMR
d/ppm 19.7 (ArCH3), 63.4 (CH2OH), 125.7 (2!CH), 125.9
(CH), 126.0 (CH), 126.1 (CH), 127.9 (2!CH), 128.0 (CH),
130.0 (CH), 130.1 (CH), 132.2 (C), 132.9 (C), 135.4 (C),
136.9 (C), 137.1 (C), 137.6 (C); MS (EI) m/z (%): 248 (MC,
60), 230 (100), 218 (20), 215 (69), 202 (34), 82 (19);

S. S. Moleele et al. / Tetrahedron 62 (2006) 2831–2844
2843
HRMS calculated for C18H16O MC 248.1201, found
248.1248.
235 (26), 202 (24), 159 (12), 94 (32), 82 (85); HRMS
calculated for C18H16O2 MC 264.1150, found 264.1146.
3.1.60. [6-Methoxy-1-(o-tolyl)naphthalen-2-yl]methanol
27d. In the same way as described above, sodium
borohydride (0.02 g, 0.678 mmol) was used to convert
carbaldehyde 26d (0.15 g, 0.543 mmol) in ethanol (5 mL)
into the alcohol 27d, produced as a light yellow oil (0.14 g,
93%). IR nmax (cmK1) 3405 (s, broad, OH stretch), 1625,
1598, 1576 (s, C]C stretch); 1H NMR d/ppm 7.78 (1H, d,
JZ8.4 Hz, 4-H), 7.64 (1H, d, JZ8.4 Hz, 3-H), 7.36–7.24
(3H, m, 3!ArH), 7.18–7.12 (3H, m, 3!ArH), 7.00 (1H,
dd, JZ9.2, 2.6 Hz, 7-H), 4.45 (2H, s, CH2OH), 3.91 (3H, s,
OCH3), 1.91 (3H, s, ArCH3); 13C NMR d/ppm 19.7
(ArCH3), 55.3 (OCH3), 63.3 (CH2OH), 105.9 (CH), 118.7
(CH), 125.8 (CH), 126.5 (CH), 126.7 (CH), 127.7 (CH),
127.8 (CH), 129.9 (CH), 130.0 (CH), 133.2 (C), 134.2 (C),
136.9 (C), 137.2 (C), 137.7 (C), 157.5 (C) (one quaternary
carbon missing); MS (EI) m/z (%): 278 (MC, 19), 260 (14),
129 (15), 108 (43), 84 (63), 82 (100), 46 (20);
HRMS calculated for C19H18O2 MC 278.1306, found
278.1297.
3.1.57. [6-Methoxy-1-(3,4,5-trimethoxyphenyl)naphtha-
len-2-yl]methanol 27a. Using the same procedure as
described above, carbaldehyde 26a (0.18 g, 0.511 mmol)
in ethanol (5 mL) was converted into the alcohol 27a
produced as white flakes (0.16 g, 89%) using sodium
borohydride (0.02 g, 0.638 mmol). MpZ163–164 8C; IR
nmax (cmK1), 1690 (s, C]O stretch), 1623 (s, C]C
stretch); 1H NMR d/ppm 7.79 (1H, d, JZ8.5 Hz, 4-H),
7.63 (1H, d, JZ8.5 Hz, 3-H), 7.44 (1H, d, JZ9.2 Hz,
8-H), 7.17 (1H, d, JZ2.5 Hz, 5-H), 7.06 (1H, dd, JZ9.2,
2.6 Hz, 7-H), 6.52 (2H, s, 20 and 60-H), 4.58 (2H, s,
CH2OH), 3.95 (3H, s, OCH3), 3.92 (3H, s, OCH3), 3.82
(6H, s, 2!OCH3); 13C NMR d/ppm 55.3 (OCH3), 56.1
(2!OCH3), 60.9 (OCH3), 63.4 (CH2OH), 105.7 (CH),
107.1 (2!CH), 118.7 (CH), 126.5 (CH), 126.8 (CH),
128.0 (C), 128.2 (CH), 133.3 (C), 133.7 (C), 134.1 (C),
137.1 (C), 138.0 (C), 153.1 (2!C), 157.5 (C); MS (EI)
m/z (%): 354 (MC, 42), 304 (100), 264 (23), 213 (35),
175 (21), 152 (11); HRMS calculated for C21H22O5 MC
354.1467, found 354.1448.
Acknowledgements
3.1.58. [6-Methoxy-1-(1-naphthyl)naphthalen-2-yl]-
methanol 27b. Sodium borohydride (0.03 g, 0.880 mmol)
was used as explained above to convert carbaldehyde 26b
(0.22 g, 0.704 mmol) in ethanol (8 mL) into the alcohol
27b, as a light brown solid (0.21 g, 95%). MpZ142–
143 8C; IR nmax (cmK1) 3366 (s, broad, OH stretch), 1625,
This work was supported by the National Research
Foundation (NRF, GUN 2053652), Pretoria, and the
University of the Witwatersrand (University and Science
Faculty Research Councils). Dr. W. A. L. van Otterlo is
thanked for many helpful discussions. Dr. E. M. Mmutlane
is thanked for helping with some of the initial experimen-
tation. We also gratefully acknowledge the Mellon
Postgraduate Mentoring Programme (sponsored by the
Andrew W. Mellon Foundation) for generous funding for
Mr. S. S. Moleele. Mr. R. Mampa and Mr. T. van der Merwe
are also thanked for providing the NMR and MS
spectroscopy services, respectively.
1
1598, 1579 (m, C]C stretch); H NMR d/ppm 7.96–7.92
(2H, m, 2!ArH), 7.87 (1H, d, JZ8.5 Hz, ArH), 7.73
(1H, d, JZ8.5 Hz, ArH), 7.59 (1H, d, JZ7.1 Hz, ArH),
7.57 (1H, d, JZ8.2 Hz, ArH), 7.48–7.43 (1H, m, ArH),
7.39 (1H, d, JZ7.0 Hz, ArH), 7.28–7.18 (3H, m, 3!
ArH), 7.07 (1H, d, JZ9.2 Hz, 8-H), 6.90 (1H, dd, JZ9.2,
2.5 Hz, 7-H), 4.37 (2H, s, CH2OH), 3.91 (3H, s, OCH3);
13C NMR d/ppm 55.3 (OCH3), 63.4 (CH2OH), 105.8
(CH), 118.7 (CH), 125.4 (CH) 125.8 (CH), 126.0 (CH),
126.4 (CH), 126.6 (CH), 127.1 (CH), 127.8 (CH), 128.0
(CH), 128.2 (CH), 128.3 (CH), 128.5 (C), 132.8 (C),
133.6 (C), 134.2 (C), 134.5 (C), 135.8 (C), 135.9 (C),
157.5 (C); MS (EI) m/z (%): 315 (MC1, 24), 314 (MC,
100), 252 (16), 239 (17), 218 (39), 130 (14), 68 (28);
HRMS calculated for C22H18O2 MC 314.1307, found
314.1352.
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