Synthesis of functionalized triarylmethanes by combination of FeCl3-catalyzed benzylations of acetylacetone with [3+3] cyclocondensations

Article abstract of DOI:10.1016/j.tet.2010.01.022

Functionalized triarylmethanes are prepared in two steps by FeCl₃-catalyzed benzylation of acetylacetone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes

Full text of DOI:10.1016/j.tet.2010.01.022

Tetrahedron 66 (2010) 1643–1652
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Synthesis of functionalized triarylmethanes by combination of FeCl3-catalyzed
benzylations of acetylacetone with [3þ3] cyclocondensations
,
Rasheed Ahmad Khera a, Ihsan Ullah a, Rasheed Ahmad a, Abdolmajid Riahi a b, Nguyen Thai Hung a,
,
b
,
,b,
*
Muhammad Sher a c, Alexander Villinger a, Christine Fischer b, Peter Langer a
a
¨
Institut fu¨r Chemie, Universitat Rostock, Albert-Einstein-Str. 3a, 18059 Rostock, Germany
b Leibniz-Institut fu¨r Katalyse e. V. an der Universita¨t Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
c Department of Chemistry, Allama Iqbal Open University, Islamabad, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
Functionalized triarylmethanes are prepared in two steps by FeCl3-catalyzed benzylation of acetylace-
tone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3þ3] cyclization of the latter
with 1,3-bis(trimethylsilyloxy)-1,3-dienes.
Received 19 October 2009
Received in revised form 30 December 2009
Accepted 5 January 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Available online 11 January 2010
Keywords:
Arenes
Catalysis
Cyclizations
Silyl enol ethers
OH
OH
1. Introduction
O
S
O
S
Triarylmethanes are of considerable pharmacological rele-
vance, which includes, for example, oestrogen receptor binding
affinity,1a inhibition of hepatic cholesterol,1b inhibition of aldose
reductase 2,1c antiproliferative activity,1d antiviral and cytotoxic
activity,1e antifungal activity,1f anti-HIV activity,1g,h and CNS acti-
vity.1i (1,1-Diphenylmethyl)salicylates and related structures have
been reported to possess anti-HIV activity,3a,1g and antibacterial
activity.3b Naturally occurring triarylmethanes, containing a (1,1-
diphenylmethyl)phenol substructure, include mohsenone, cha-
maechromone and a number of related molecules.2 Products A
and B were isolated as natural products formed by metabolism of
commercial preparations of phenol red, a pH indicator dye often
used in cell culture media (Scheme 1).1a The isolation of some
substituted triphenylmethanes, such as C and D, from the leaves
of the cajeput tree Melaleuca quinqueneruia (Myrtaceae) was also
reported.2
H
N
O
O
O
HO
HO
B
A
Me
OMe
MeO
OMe
OMe
MeO
MeO
MeO
OMe
MeO
MeO
OMe
OMe
D
C
Scheme 1. Triarylmethane natural products.
The scope of classic syntheses of di- and triarylmethanes, based
on Friedel–Crafts alkylations, is limited by the drastic reaction
conditions and by the formation of regioisomeric mixtures or
isomerization products. These problems can be overcome by novel
FeCl3$6H2O-catalyzed Friedel–Crafts type benzylations of arenes
using simple benzylic alcohols under mild conditions and with high
region- and chemoselectivity.4 In this context, FeCl3-catalyzed
conjugate additions of 1,3-dicarbonyl compounds to enones5 and
condensation of 1,3-dicarbonyl compounds to simple benzylic
alcohols have been reported.6,7
* Corresponding author. Institut fu¨ r Chemie, Universita¨t Rostock, Albert-Einstein-
Str. 3a, 18059 Rostock, Germany. Fax: þ49 381 4986412.
E-mail address: peter.langer@uni-rostock.de (P. Langer).
0040-4020/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.01.022

1644
R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
All attempts to directly prepare sterically encumbered and
Me3SiO
R3
OSiMe3
OR4
functionalized triarylmethanes and diarylmethanes, such as 2,6-
disubstituted or hydroxylated derivatives, by Fe-catalyzed reaction
of arenes with benzylalcohols failed in our hands. In addition, the
synthesis of the starting materials, highly substituted and func-
tionalized arenes, proved to be not an easy task. Therefore, we
have envisaged an alternative approach to triarylmethanes by
OH O
TiCl4
CH2Cl2
R3
OR4
5a-l
+
Me3SiO
Me
O
Me
Me
_
78 to 20 °C
14 h
R1
R2
Me
R1
R2
development of
a building block strategy. Some years ago,
6a-af
4a-g
Chan et al. developed8 a convenient approach to salicylates by
formal [3þ3] cyclizations9 of 1,3-bis(trimethylsilyloxy)-1,3-di-
enes10 with 3-trimethylsilyloxy-2-en-1-ones. Recently, we have
reported the synthesis of sterically encumbered and functionalized
triarylmethanes by a combined FeCl3-catalyzed benzylation/[3þ3]
cyclocondensation approach.11 Herein, we report full details and
a comprehensive study related to the scope. The products reported
herein are not readily available by other methods and have, to the
best of our knowledge, not yet been prepared.
TiCl4
_
H2O
O
O
R3
TiCl4
OR4
Me3SiO
O
+
OTiCl3
Me
Me
Me
Me
R1
R2
R1
R2
H
E
5a-l
2. Results and discussion
Me3SiCl
Me3SiCl
The FeCl3$6H2O-catalyzed benzylation of acetylacetone (2) with
benzylalcohols 1a–g, following conditions reported by Beller et al.,6
afforded products 3a–g in very good yields (Scheme 2, Table 1).11
The silylation of 3a–g afforded the 3-silyloxy-2-en-1-ones 4a–g.
O
O
Me3SiO
R3
OR4
TiCl3
Me3SiO
R3
OR4
TiCl4
Me3SiCl
O
O
Me3SiO
Me
R1
Me
O
O
Me
(Me3Si)2O
Me
O
O
R2
R1
R2
Me
Me
2
Me
Me
F
i
G
OH
R1 R2
3a-g
Scheme 3. Possible mechanism of the formation of 6(a–af).
+
R1 R2
1a-g
Table 2
Synthesis of di- and triarylmethanes 6a–af
ii
Me3SiO
Me
O
4
5
6
R1
R2
R3
R4
% (6)a
Me
a
a
a
a
a
a
a
a
a
a
b
b
b
b
b
b
b
b
c
c
c
c
c
c
c
c
d
d
e
f
g
g
a
b
c
d
e
f
g
h
i
a
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
H
H
H
Me
Me
Et
Me
Et
PhCH2
Me
Et
42
45
65
31
40
42
43
46
50
57
33
37
68
39
41
53
53
55
50
53
69
40
43
42
53
57
32
37
55
72
46
47
R1 R2
4a-g
b
c
Ph
Ph
d
e
Ph
Ph
Scheme 2. Synthesis of 4a–g, i: FeCl3$6H2O, NO2CH3, 50 ꢀC, 4 h; ii: Me3SiCl, NEt3,
C6H6, 20 ꢀC, 72 h.
f
Ph
Me
Et
g
Ph
Et
h
i
Ph
Ph
nBu
nOct
nDec
H
H
H
Me
Et
nBu
nNon
nDec
H
Me
Me
Me
Me
Et
Table 1
Ph
Ph
Synthesis of 3a–g and 4a–g
j
j
Ph
a
b
c
e
f
h
k
j
a
b
c
d
e
f
k
l
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-(MeO)C6H4
4-(MeO)C6H4
Me
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-FC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-(MeO)C6H4
4-(MeO)C6H4
Ph
3,4
R1
R2
% (3)a
% (4)a
a
b
c
d
e
f
Ph
Ph
91
87
85
88
94
95
86
90
89
92
91
81
90
90
m
n
o
p
q
r
s
t
u
v
w
x
PhCH2
Et
4-FC6H4
4-ClC6H4
4-(MeO)C6H4
Me
4-FC6H4
4-ClC6H4
4-(MeO)C6H4
Ph
4-BrC6H4
4-(MeO)C6H4
Me
Me
Me
Me
Me
Et
PhCH2
Me
Et
Me
Me
Me
Me
Et
Me
PhCH2
Et
Me
Me
g
a
Isolated yields.
H
H
Me
Me
Et
nPent
nDec
H
H
H
H
H
The TiCl4-mediated formal [3þ3] cyclocondensation of 4a–g
with 1,3-bis(silyloxy)-1,3-dienes 5a–l, available from the corre-
sponding 1,3-dicarbonyl compounds in two steps,8 afforded the
triarylmethanes 6a–af (Scheme 3, Table 2). During the optimiza-
tion, it proved to be important to carry out the reactions in a highly
concentrated solution.
The formation of 6a–af can be explained by reaction of 4a–g
with TiCl4 to give intermediates E. The attack of the terminal
carbon atom of 5a–l onto E afforded intermediates F. The elimi-
nation of hexamethyldisiloxane (intermediates G) and subsequent
cyclization gave intermediates H. The elimination of titanium
hydroxide (before or during the aqueous work-up) and aromati-
zation resulted in the formation of products 6a–af. Due to the
symmetrical structure of E, the attack of 5a–l on either terminal
l
j
y
z
a
b
a
c
b
g
aa
ab
ac
ad
ae
af
Me
Me
Me
4-BrC6H4
4-(MeO)C6H4
4-(MeO)C6H4
Et
Me
a
Isolated yields.
allylic carbon atom would result in the formation of the same
products (6a–af). The yields depended on the type of substrate
employed. The best yields were obtained for those products

R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
1645
derived from diene 5c (prepared from benzyl acetoacetate). The
yields of triarylmethanes derived from C4-unsubstituted dienes
5a,b were similar to those derived from substituted dienes 5d–l.
The yield of diarylmethanes 6ac–af were similar to those of tri-
arylmethanes 6a–ab (comparing the same type of diene and aryl
group R2). The aryl groups seem to have no major influence on the
yield.
The structures of 6a–af were established by spectroscopic
methods. The structures of 6n, 6s and 6ad were independently
confirmed by X-ray crystal structure analyses (Figs. 1–3).12 Triar-
ylmethanes 6n and 6s adopt a propeller-type structure, due to
steric interaction of the aryl with the methyl groups. Intramolecular
hydrogen bonds O–H/O are observed in solution and in the solid
state.
In conclusion, a variety of functionalized and sterically encum-
bered triarylmethanes were prepared by combination of FeCl3-
catalyzed benzylations of 1,3-diketones and formal [3þ3] cyclo-
condensation reactions. The products are not readily available by
other methods.
Figure 3. Ortep plot of 6ad.
3. Experimental section
3.1. General comments
All solvents were dried by standard methods and all reactions
were carried out under an inert atmosphere. For 1H and 13C NMR
spectra the deuterated solvents indicated were used. Mass spec-
trometric data (MS) were obtained by electron ionization
(EI, 70 eV), chemical ionization (CI, isobutane) or electrospray
ionization (ESI). For preparative scale chromatography silica gel 60
(0.063–0.200 mm, 70–230 mesh) was used.
3.1.1. General procedure for the synthesis of 3-substituted pentane-
2,4-diones (3a–g). In a pressure tube, FeCl3$6H2O (5 mol %), 1a–g
(5.0 mmol) and acetylacetone (20.0 mmol) were dissolved in 10 mL
of nitromethane. After stirring for 4 h at 50 ꢀC, the reaction was
quenched with water followed by extraction with dichloro-
methane. The combined organic layers were dried over Na2SO4.
Then, products 3a–g were purified by column chromatography
(heptanes/ethyl acetate¼1:1).
3.1.2. 3-Benzhydrylpentane-2,4-dione (3a). Starting with FeCl3$6H2O
(0.067 g, 5 mol %), 1a (0.92 g, 5.0 mmol), acetylacetone (2.0 g,
20.0 mmol), 3a was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a colourless oil (1.21 g, 91%). 1H NMR (250 MHz,
Figure 1. Ortep plot of 6n.
CDCl3):
d
¼2.02 (s, 6H, CH3), 4.75 (d, J¼11.5 Hz, CH), 4.84 (d, J¼11.6 Hz,
CH), 7.17–7.29 (m, 10H, CHAr). 13C NMR (62 MHz, CDCl3):
d¼29.6
(CH3), 51.2, 74.5 (CH), 127.0, 127.7, 128.9 (CHAr),141.2 (CAr), 202.9 (CO).
(IR (KBr), cmꢁ1): 3081 (w), 3019 (w), 2962 (w), 2925 (w), 2870 (w),
1651 (s), 1598 (m), 1563 (m), 1494 (m), 1444 (m), 1603 (s), 1507 (s),
1297 (m), 1246 (s), 1159 (m), 1095 (m), 1014 (w), 849 (s), 786 (s), 506
(w). MS (EI, 70 eV): m/z (%)¼266 ([M]þ, 64), 251 (45), 165 (43), 148
(34), 143 (100), 129 (6), 95 (48), 85 (15), 75 (26), 69 (54), 50 (45), 43
(26). HRMS (EI): Calcd for C18H18O2 ([M]þ): 266.13068; found:
266.130655.
3.1.3. 3-(Bis(4-fluorophenyl)methyl)pentane-2,4-dione
(3b). Starting with FeCl3$6H2O (0.067 g, 5 mol %), 1b (1.10 g,
5.0 mmol), acetylacetone (2.0 g, 20.0 mmol), 3b was isolated as
a white crystalline solid (1.31, 87%), mp 102–104 ꢀC. 1H NMR
(250 MHz, CDCl3):
(d, J¼11.6 Hz, CH), 6.95–7.01 (m, 4H, CHAr), 7.19–7.24 (m, 4H, CHAr).
13C NMR (62 MHz, CDCl3):
d
¼2.02 (s, 6H, CH3), 4.65 (d, J¼11.7 Hz, CH), 4.82
d
¼29.6 (CH3), 49.5, 74.8 (CH), 115.9 (d,
JC,F¼21.6 Hz, CHAr), 129.2 (d, JC,F¼8.1 Hz, CHAr), 136.9 (d, JC,F¼3.1 Hz,
CAr), 162.2 (d, JC,F¼245.8 Hz, CAr), 202.4 (CO). (IR (KBr), cmꢁ1): 2954
(w), 2922 (w), 2855 (w), 1650 (s), 1661 (m), 1573 (m), 1612 (s), 1527
Figure 2. Ortep plot of 6s.

1646
R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
(m), 1297, 1245 (m), 1212 (s), 1134 (m), 1023 (w), 1014 (m), 848 (s),
788 (s), 545 (w). MS (EI, 70 eV): m/z (%)¼302 ([M]þ, 64), 287 (66),
259 (6),183 (100),109 (16), 95 (48), 85 (14), 75 (50), 69 (54), 50 (45),
43 (53). HRMS (EI): Calcd for C18H16F2O2 ([M]þ): 302.11184; found:
302.111765.
13C NMR (75 MHz, CDCl3):
d¼20.9, 29.6, 29.8, 39.7 (CH3), 55.2 (OCH3),
76.6 (CH), 114.6, 128.2 (CHAr), 134.9, 158.4 (CAr), 203.5, 203.6 (CO). (IR
(KBr), cmꢁ1): 2957 (w), 2935 (w), 2834 (w),1712 (s),1554,1529,1456,
1324 (m),1277(s),1246 (s),1157 (m),1095 (s),1056 (w), 847 (s), 773 (s),
645(w). MS (EI, 70 eV): m/z (%)¼234 ([M]þ, 64), 165 (66), 138 (6), 123
(100), 109 (6), 95 (48), 85 (11), 75 (20), 69 (50), 50 (5), 43 (23). HRMS
(EI): Calcd for C14H18O2 ([M]þ): 234.12559; found: 234.125855.
3.1.4. 3-(Bis(4-chlorophenyl)methyl)pentane-2,4-dione
(3c). Starting with FeCl3$6H2O (0.067 g, 5 mol %), 1c (1.26 g,
5.0 mmol), acetylacetone (2.0 g, 20.0 mmol), 3c was isolated as
a white crystalline solid (1.41, 85%), mp 142–144 ꢀC. 1H NMR
3.1.9. General procedure for the synthesis of silyl enol ethers (4a–g). To
a stirred benzene solution (2.5 L/1.0 mol of 3a–g), of (5.0 mmol) and
triethylamine (7.5 mmol) was added. After stirring of the solution for
2 h, trimethylchlorosilane (9.0 mmol) was added. After stirring of the
solution for 72 h, the solvent was removed in vacuo and hexane
(25 mL) was added to the residue to give a suspension. The latter was
filtered under argon atmosphere. The filtrate was concentrated in
vacuo to give silyl enol ethers 4a–g. Due to their unstable nature,
compounds 4 could only be characterized by 1H NMR spectroscopy.
(250 MHz, CDCl3):
4.79 (d, J¼11.7 Hz, 1H, CH), 7.14–7.18 (m, 4H, CHAr), 7.22–7.27 (m,
4H, CHAr). 13C NMR (62 MHz, CDCl3):
d
¼2.01 (s, 6H, CH3), 4.63 (d, J¼11.8 Hz, 1H, CH),
d
¼29.6 (CH3), 49.7, 74.9 (CH),
114.2, 128.6 (CHAr), 133.7, 158.3 (CAr), 203.2 (CO). (IR (KBr), cmꢁ1):
2928 (w), 2855 (w), 1735 (w), 1659 (s), 1609 (s), 1407 (m), 1324 (m),
1309 (m),1297 (s),1254 (m),1243 (m),1158 (m),1088 (m),1022 (w),
846 (s), 754 (s), 554 (w). MS (EI, 70 eV): m/z (%)¼334 ([M]þ, 84), 319
(34), 291 (65), 165 (54), 135 (6), 123 (43), 109 (100), 96 (48), 87 (11),
75 (67), 69 (26), 50 (5), 43 (23). HRMS (EI): Calcd for C18H16Cl2O2
([M]þ): 334.05274; found: 334.052365.
3.1.10. 3-Benzhydryl-4-(trimethylsilyloxy)pent-3-en-2-one
(4a). Starting with benzene (12.5 mL), 3a (1.33 g, 5.0 mmol), trie-
thylamine (0.76 g, 7.5 mmol) and trimethylchlorosilane (0.98 g,
9.0 mmol), 4a was isolated as a reddish oil (1.52 g, 90%). 1H NMR
3.1.5. 3-(Bis(4-methoxyphenyl)methyl)pentane-2,4-dione
(3d). Starting with FeCl3$6H2O (0.067 g, 5 mol %), 1d (1.22 g,
5.0 mmol), acetylacetone (2.0 g, 20.0 mmol), 3d was isolated as
a white crystalline solid (1.43 g, 88%), mp 125–127 ꢀC. 1H NMR
(250 MHz, CDCl3):
CH3), 5.48 (s, 1H, CH), 7.17–7.27 (m, 10H, CHAr).
d
¼0.19 (s, 9H, 3 CH3),1.91 (s, 3H, CH3), 2.17 (s, 3H,
(250 MHz, CDCl3):
J¼11.8 Hz, 1H, CH), 4.63 (d, J¼11.7 Hz, 1H, CH), 6.70–6.73 (m, 4H,
CHAr), 7.06–7.09 (m, 4H, CHAr). 13C NMR (62 MHz, CDCl3):
¼29.6
d
¼1.92 (s, 6H, CH3), 3.67 (s, 6H, OCH3), 4.54 (d,
3.1.11. 3-(Bis(4-fluorophenyl)methyl)-4-(trimethylsilyloxy)-pent-3-
en-2-one (4b). Starting with benzene (12.5 mL), 3a (1.51 g,
5.0 mmol), triethylamine (0.76 g, 7.5 mmol) and trimethyl-
chlorosilane (0.98 g, 9.0 mmol), 4a was isolated as a reddish oil
d
(CH3), 49.7 (CH), 55.1 (OCH3), 74.9 (CH), 114.2, 128.6 (CHAr), 133.7,
158.3 (CAr), 203.2 (CO). (IR (KBr), cmꢁ1): 2951 (w), 2928 (w), 2830
(w), 1608 (s), 1547 (m), 1287(m), 1246 (s), 1159 (m), 1145 (m), 1095
(s), 1014 (w), 849 (s), 743 (m), 506 (w). MS (EI, 70 eV): m/z (%)¼326
([M]þ, 64), 283 (34) 265 (66), 238 (100), 183 (32), 108 (63), 95 (48),
85 (13), 75 (24), 69 (53), 50 (25), 43 (53). HRMS (EI): Calcd for
C20H22O4 ([M]þ): 326.15181; found: 326.151265.
(1.66 g, 89%). 1H NMR (250 MHz, CDCl3):
d
¼0.19 (s, 9H, CH3), 2.02 (s,
3H, CH3), 2.06 (s, 3H, CH3), 5.55 (s, 1H, CH), 7.01–7.22 (m, 2H, CHAr),
7.19–7.31 (m, 4H, CHAr).
3.1.12. 3-(Bis(4-chlorophenyl)methyl)-4-(trimethylsilyloxy)-pent-3-
en-2-one (4c). Starting with benzene (12.5 mL), 3a (1.67 g,
5.0 mmol), triethylamine (0.76 g, 7.5 mmol) and trimethyl-
chlorosilane (0.98 g, 9.0 mmol), 4a was isolated as a reddish oil
3.1.6. 3-(1-Phenylethyl)pentane-2,4-dione
(3e). Starting
with
FeCl3$6H2O (0.067 g, 5 mol %), 1e (0.61 g, 5.0 mmol), acetylacetone
(2.0 g, 20.0 mmol), 3e was isolated as a white crystalline solid (0.96,
(1.87 g, 92%). 1H NMR (250 MHz, CDCl3):
3H, CH3), 2.03 (s, 3H, CH3), 5.68 (s, 1H, CH), 7.85–7.89 (m, 2H, CHAr),
7.89–7.96 (m, 2H, CHAr).
d
¼0.18 (s, 9H, CH3), 2.01 (s,
94%), mp 112–114 ꢀC.1H NMR (250 MHz, CDCl3):
d
¼1.19 (d, J¼7.0 Hz,
3H, CH3), 1.80 (s, 3H, CH3), 2.23 (s, 3H, CH3), 3.55–3.63 (m, 1H, CH),
4.02 (d, J¼11.5 Hz, 1H, CH), 7.13 (–CH), 126.9, 127.2, 128.7 (CHAr),
143.0 (CAr), 203.3, 203.4 (CO). (IR (KBr), cmꢁ1): 2950 (w), 2927 (w),
2829 (w),1608 (s),1547 (m),1605 (s),1534,1434,1389 (m),1283(m),
1254 (w),1146 (m),1097 (s),1033 (w), 845 (s), 785 (s), 576(w). MS(EI,
70 eV): m/z (%)¼204 ([M]þ,44),189 (34),175 (36),138 (46),125 (100),
109 (65), 95 (48), 85 (11), 75 (20), 69 (50), 43 (23). HRMS (EI): Calcd
for C13H16O2 ([M]þ): 204.11503; found: 204.115651.
3.1.13. 3-(Bis(4-methoxyphenyl)methyl)-4-(trimethylsilyloxy)-pent-
3-en-2-one (4d). Starting with benzene (12.5 mL), 3d (1.63 g,
5.0 mmol), triethylamine (0.76 g, 7.5 mmol) and trimethyl-
chlorosilane (0.98 g, 9.0 mmol), 4a was isolated as a reddish oil(1.81 g,
91%).1HNMR(250 MHz, CDCl3):
d¼0.16(s,9H, CH3),3.79(s, 6H, OCH3),
5.39 (s, 1H, CH), 6.96–7.06 (m, 4H, CHAr), 7.35–7.45 (m, 4H, CHAr).
3.1.14. 3-(1-Phenylethyl)-4-(trimethylsilyloxy)pent-3-en-2-one
(4e). Starting with benzene (12.5 mL), 3e (1.02 g, 5.0 mmol), trie-
thylamine (0.76 g, 7.5 mmol) and trimethylchlorosilane (0.98 g,
9.0 mmol), 4e was isolated as a reddish oil (1.12 g, 81%). 1H NMR
3.1.7. 3-(1-(4-Bromophenyl)ethyl)pentane-2,4-dione (3f). Starting
with FeCl3$6H2O (0.067 g, 5 mol %), 1f (1.00 g, 5.0 mmol), acetyla-
cetone (2.0 g, 20.0 mmol), 3f was isolated as a white crystalline
solid (1.35, 95%), mp 112–114 ꢀC. 1H NMR (250 MHz, CDCl3):
d¼1.11
(250 MHz, CDCl3):
d
¼0.15 (m, 9H, CH3), 1.28 (s, 3H, CH3), 1.34
(d, J¼7.0 Hz, 3H, CH3), 1.79 (s, 3H, CH3), 2.18 (s, 3H, CH3), 3.44–3.56
(m, 1H, CH), 3.92 (d, J¼11.7 Hz, 1H, CH), 6.98–7.01 (m, 2H, CHAr),
(s, 3H, CH3), 1.43 (d, J¼8.6 Hz, 3H, CH3), 4.12 (q, J¼8.1 Hz, 1H, CH),
6.82–7.22 (m, 4H, CHAr).
7.33–7.36 (m, 2H, CHAr). 13C NMR (62 MHz, CDCl3):
29.7 (CH3), 39.6, 76.4 (CH), 120.7 (CAr), 129.0, 131.9 (CHAr), 142.1
(CAr), 202.9, 203.0 (CO).
d
¼20.6, 29.5,
3.1.15. 3-(1-(4-Bromophenyl)ethyl)-4-(trimethylsilyloxy)pent-3-en-
2-one (4f). Starting with benzene (12.5 mL), 3f (1.00 g, 5.0 mmol),
triethylamine (0.76 g, 7.5 mmol) and trimethylchlorosilane (0.98 g,
9.0 mmol), 4f was isolated as a reddish oil (1.60 g, 90%). 1H NMR
3.1.8. 3-(1-(4-Methoxyphenyl)ethyl)pentane-2,4-dione
(3g). Starting with FeCl3$6H2O (0.067 g, 5 mol %), 1g (0.76 g,
5.0 mmol), acetylacetone (2.0 g, 20.0 mmol), 3g was isolated as
a white crystalline solid (1.01, 86%), mp 138–140 ꢀC. 1H NMR
(250 MHz, CDCl3):
d
¼0.17 (m, 9H, CH3), 1.44 (d, J¼8.7 Hz, 3H, CH3),
1.62 (s, 3H, CH3),1.72 (s, 3H, CH3), 4.11 (q, J¼8.6 Hz,1H, CH), 7.07–7.11
(m, 4H, CHAr).
(300 MHz, CDCl3):
(s, 3H, CH3), 3.41–3.53 (m, 1H, CH), 3.70 (s, 3H, OCH3), 3.91
d
¼1.11 (d, J¼6.9 Hz, 3H, CH3), 1.76 (s, 3H, CH3), 1.78
3.1.16. 3-(1-(4-Methoxyphenyl)ethyl)-4-(trimethylsilyloxy)pent-3-
(d, J¼11.7 Hz,1H, CH), 6.73–6.77 (m, 2H, CHAr), 7.01–7.04(m, 2H, CHAr).
en-2-one (4g). Starting with benzene (12.5 mL), 3g (0.76 g,

R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
1647
5.0 mmol), triethylamine (0.76 g, 7.5 mmol) and trimethyl-
MS (EI, 70 eV): m/z (%)¼422 (Mþ, 6), 314 (19), 288 (36), 287 (10),
273 (40), 211 (12), 195 (17), 178 (10), 167 (27), 166 (34), 165 (61), 152
(16), 115 (10), 92 (20), 91 (100), 89 (10), 79 (13), 78 (14), 77 (18), 65
(22), 63 (10), 55 (10), 51 (12), 44 (36), 43 (13), 41 (14). HRMS (EI):
calcd for C29H26O3 [M]þ: 422.18765; found: 422.188014.
chlorosilane (0.98 g, 9.0 mmol), 4g was isolated as a reddish oil
(1.53 g, 90%). 1H NMR (250 MHz, CDCl3):
(d, J¼8.6 Hz, 3H, CH3), 1.64 (s, 3H, CH3), 1.73 (s, 3H, CH3), 3.89 (s, 3H,
OCH3), 4.12 (q, J¼8.2 Hz, 1H, CH), 7.06–7.12 (m, 2H, CHAr), 7.16–7.20
(m, 2H, CHAr).
d
¼0.16 (m, 9H, CH3), 1.42
3.1.21. Methyl 3-diphenylmethyl-6-hydroxy-2,4,5-trimethylbenzoate
(6d). Starting with 4a (0.510 g, 1.5 mmol) and 5d (0.452 g,
1.65 mmol), 6d was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a colourless oil (0.167 g, 31%). 1H NMR
(300 MHz, CDCl3): 1.91 (s, 3H, CH3), 2.10 (s, 6H, CH3), 3.81 (s, 3H,
OCH3), 5.99 (s, 1H, CH), 7.00–7.21 (m, 10H, CHAr), 10.77 (s, 1H, OH).
3.1.17. General procedure for the synthesis of 6(a–af). To a CH2Cl2
solution (2 L/1.0 mol of 4a–g) of 4a–g was added 5a–l (1.1 mmol)
and, subsequently, TiCl4 (1.1 mmol) at ꢁ78 ꢀC. The temperature of
the solution was allowed to warm to 20 ꢀC during 14 h with stirring.
To the solution was added hydrochloric acid (10%, 20 mL) and the
organic and the aqueous layer were separated. The latter was
extracted with CH2Cl2 (3ꢂ20 mL). The combined organic layers
were dried (Na2SO4), filtered and the filtrate was concentrated in
vacuo. The residue was purified by chromatography (silica gel,
heptanes/EtOAc) to give 6(a–af).
13C NMR (CDCl3, 75 MHz):
d
¼18.0, 20.0, 28.6 (CH3), 50.1 (CH), 50.9
(OCH3), 111.0, 122.2 (CAr), 124.8, 127.0, 128.0 (CHAr), 132.0, 135.7,
141.4, 142.7 (CAr), 156.8 (COH), 171.6 (CO). IR (neat, cmꢁ1): 3082 (w),
3060 (w), 3024 (w), 2953 (w), 2923 (w), 2853 (w), 1648 (s), 1596
(m), 1563 (m), 1492 (m), 1433 (m), 1394 (m), 1343 (m), 1311 (m),
1231 (s), 1205 (s), 1169 (m), 1097 (m), 1049 (m), 1022 (m), 947 (w),
841 (m), 799 (m), 738 (m), 697 (s), 622 (m), 615 (m), 585 (m) 578
(m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼360 (Mþ, 34), 329 (24), 328
(100), 300 (14), 285 (20), 223 (12), 222 (11), 179 (10), 178 (10), 167
(16), 166 (12), 165 (36), 152 (10), 91 (10). HRMS (EI): calcd for
C24H24O3 [M]þ: 360.17200; found: 360.171717.
3.1.18. Methyl 3-diphenylmethyl-6-hydroxy-2,4-dimethylbenzoate
(6a). Starting with 4a (0.510 g, 1.5 mmol) and 5a (0.429 g,
1.65 mmol), 6a was isolated after chromatography (silica gel, n-
heptane/EtOAc) as a colourless oil (0.22 g, 42%). 1H NMR (300 MHz,
CDCl3):
5.92 (s, 1H, CH), 6.65 (s, 1H, CHAr), 6.99–7.21 (m, 10H, CHAr), 10.51 (s,
1H, OH). 13C NMR (CDCl3, 62 MHz):
¼20.3, 21.7 (CH3), 49.7 (CH),
d¼1.98 (s, 3H, CH3), 2.07 (s, 3H, CH3), 3.79 (s, 3H, OCH3),
d
3.1.22. Ethyl 3-diphenylmethyl-6-hydroxy-2,4,5-trimethylbenzoate
(6e). Starting with 4a (0.510 g, 1.5 mmol) and 5e (0.476 g,
1.65 mmol), 6e was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a colourless oil (0.234 g, 40%). 1H NMR
(300 MHz, CDCl3): 1.18 (t, J¼7.1 Hz, 3H, OCH2CH3), 1.79 (s, 3H,
CH3), 2.00 (s, 3H, CH3), 2.03 (s, 3H, CH3), 4.20 (q, J¼7.1 Hz, 2H,
OCH2CH3), 5.90 (s, 1H, CH), 6.91–7.12 (m, 10H, CHAr), 10.73 (s, 1H,
52.0 (OCH3), 111.7 (CAr), 117.8 (CHAr), 126.0, 128.2, 129.1 (CHAr),
132.2, 139.3 141.0, 144.3 (CAr), 158.8 (COH), 170.9 (CO). IR (neat,
cmꢁ1): 3084 (w), 3026 (w), 2959 (w), 2918 (w), 1663 (s), 1599 (m),
1564 (m), 1492 (m), 1435 (m), 1341 (m), 1265 (m), 1210 (m), 1143
(m), 1069 (m), 942 (m), 914 (w), 857 (m), 801 (m), 736 (m), 719 (s),
696 (s), 613 (m), 571 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼346 (Mþ,
66), 315 (34), 314 (100), 299 (21), 285 (14), 237 (18), 167 (14), 166
(24), 165 (49), 115 (10). HRMS (EI): calcd for C23H22O3 [M]þ:
346.15635; found: 346.156966.
OH). 13C NMR (CDCl3, 62 MHz):
d
¼13.4, 15.2, 20.2, 22.1 (CH3), 52.2
(CH), 62.6 (OCH2CH3), 113.3, 124.4 (CAr), 127.0, 129.2, 130.2 (CHAr),
134.0, 137.9, 143.6, 144.7 (CAr), 159.0 (COH), 173.3 (CO). IR (neat,
cmꢁ1): 3082 (w), 3060 (w), 3023 (w), 2981 (w), 2927 (w), 1727
(w), 1642 (s), 1596 (m), 1563 (m), 1492 (m), 1442 (m), 1379 (m),
1230 (s), 1195 (m), 1081 (m), 1025 (m), 802 (m), 721 (m), 695 (s),
665 (m), 580 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼374 (Mþ, 32), 329
(28), 328 (100), 327 (10), 300 (16), 285 (20), 223 (12), 222 (11), 179
(10), 178 (10), 167 (32), 166 (14), 165 (43), 152 (12), 91 (11). HRMS
(EI): calcd for C25H26O3 [M]þ: 374.18765; found: 374.187695.
3.1.19. Ethyl3-diphenylmethyl-6-hydroxy-2,4-dimethylbenzoate(6b).
Starting with 4a (0.510 g, 1.5 mmol) and 5b (0.452 g, 1.65 mmol), 6b
was isolated after chromatography (silica gel, n-heptane/EtOAc) as
a colourless oil (0.242 g, 45%). 1H NMR (300 MHz, CDCl3):
d
¼1.19
(t, J¼7.1 Hz, 3H, OCH2CH3),1.90 (s, 3H, CH3), 2.03 (s, 3H, CH3), 4.22 (q,
J¼7.1 Hz, 2H, OCH2CH3), 5.85 (s, 1H, CH), 6.57 (s, 1H, CHAr), 6.95–7.12
(m, 10H, CHAr), 10.52 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
d¼13.1,
20.2, 21.7 (CH3), 49.7 (CH), 60.5 (OCH2CH3), 111.8 (CAr), 116.8, 124.9,
127.1, 128.0 (CHAr), 132.1, 139.3, 141.1, 144.2 (CAr), 158.9 (COH), 170.5
(CO). IR (neat, cmꢁ1): 3082 (w), 3058 (w), 2961 (w), 2924 (w), 2871
(w),1726 (w),1654 (m),1598 (m),1568 (w),1492 (m),1449 (w),1370
(m), 1258 (s), 1224 (m), 1141 (m), 1068 (s), 1013 (s), 860 (m), 799 (s),
736 (w), 696 (s), 622 (m), 578 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼360
(Mþ, 88), 315 (66), 314 (100), 299 (26), 285 (15), 271 (10), 237 (33),
209 (10), 167 (35), 166 (26), 165 (51). HRMS (EI): calcd for C24H24O3
[M]þ: 360.17200; found: 360.171717.
3.1.23. Methyl 3-diphenylmethyl-5-ethyl-6-hydroxy-2,4-dimethyl-
benzoate (6f). Starting with 4a (0.510 g, 1.5 mmol) and 5f (0.476 g,
1.65 mmol), 6f was isolated after chromatography (silica gel, n-
heptane/EtOAc) as
a
colourless oil (0.235 g, 42%). 1H NMR
(300 MHz, CDCl3): 1.04 (t, J¼7.4 Hz, 3H, CH2CH3), 1.96 (s, 3H, CH3),
2.09 (s, 3H, CH3), 2.61 (q, J¼7.3 Hz, 2H, CH2CH3), 5.97 (s, 1H, CH),
6.94–7.26 (m, 10H, CHAr), 10.81 (s, 1H, OH). 13C NMR (CDCl3,
62 MHz):
d¼12.3, 17.6, 20.1 (CH3), 18.9 (CH2CH3), 50.2 (CH), 60.1
(OCH3), 111.3 (CAr), 124.7, 127.2, 128.5 (CHAr), 128.2, 132.2, 135.8,
141.5, 141.6 (CAr), 156.9 (COH), 171.3 (CO). IR (neat, cmꢁ1): 3082 (w),
3057 (w), 3021 (w), 2964 (w), 2928 (w), 2873 (w), 1728 (w), 1651
(s), 1598 (m), 1563 (m), 1494 (m), 1444 (m), 1371 (m), 1262 (m),
1224 (m), 1190 (s), 1104 (m), 1031 (m), 807 (m), 745 (m), 728 (m),
670 (s), 624 (w), 600 (m), 583 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼374
(Mþ, 33), 329 (26), 328 (43), 327 (100), 300 (12), 285 (10), 179 (15),
178 (17), 167 (30), 166 (16), 165 (44), 152 (14), 91 (13). HRMS (EI):
calcd for C25H26O3 [M]þ: 374.18765; found: 374.187686.
3.1.20. Benzyl 3-diphenylmethyl-6-hydroxy-2,4-dimethylbenzoate
(6c). Starting with 4a (0.510 g, 1.5 mmol) and 5c (0.555 g,
1.65 mmol), 6c was isolated after chromatography (silica gel, n-
heptane/EtOAc) as
(300 MHz, CDCl3):
OCH2), 6.65 (s, 1H, CH), 6.98–7.19 (m, 10H, CHAr), 7.24–7.29 (m, 5H,
CHAr), 10.51 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
a
colourless oil (0.410 g, 65%). 1H NMR
d
¼1.95 (s, 3H, CH3), 2.10 (s, 3H, CH3), 5.27 (s, 2H,
d¼21.4, 22.8
(CH3), 50.7 (CH), 67.3 (OCH2), 112.6 (CAr), 117.9, 126.0, 128.2, 128.4,
128.5,128.6, 129.0 (CHAr), 133.2,135.1, 140.4, 142.0, 145.6 (CAr),160.0
(COH), 171.3 (CO). IR (neat, cmꢁ1): 3082 (w), 3058 (w), 3023 (w),
2973 (w), 2928 (w), 1729 (w), 1654 (s), 1598 (m), 1566 (m), 1493
(m), 1450 (m),1379 (m),1320 (m), 1289 (m),1260 (m), 1209 (s), 1141
(m), 1140 (s), 1064 (s), 1026 (m), 969 (w), 949 (w), 908 (w), 850 (m),
3.1.24. Ethyl 3-diphenylmethyl-5-ethyl-6-hydroxy-2,4-dimethylben-
zoate (6g). Starting with 4a (0.510 g, 1.5 mmol) and 5g (0.476 g,
1.65 mmol), 6g was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a colourless oil (0.250 g, 43%). 1H NMR
(300 MHz, CDCl3): 1.03 (t, J¼7.4 Hz, 3H, CH2CH3), 1.28 (t, J¼7.2 Hz,
3H, OCH2CH3), 1.95 (s, 3H, CH3), 2.10 (s, 3H, CH3), 2.63 (q, J¼7.4 Hz,
800 (m), 748 (m), 734 (m), 717 (m), 694 (s), 614 (m), 578 (m) cmꢁ1
.

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R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
2H, CH2CH3), 4.31 (q, J¼7.1 Hz, 2H, OCH2CH3), 6.00 (s, 1H, CH), 7.02–
30.9, 31.2, 33.0 (CH2), 52.3 (CH), 53.1 (OCH3), 113.3 (CAr), 127.0, 129.3
(CHAr), 129.4 (C(Ar)), 130.3 (CHAr), 134.3, 138.0, 143.6, 144.3 (CAr),
159.0 (COH), 173.8 (CO). IR (neat, cmꢁ1): 3059 (w), 3023 (w), 2952
(m), 2921 (s), 2852 (m), 1933 (w), 1752 (m), 1703 (m), 1656 (s), 1598
(m),1493 (m),1438 (s),1377 (w),1322 (m),1293 (m),1229 (m),1201
(s),1120 (m),1047 (m),1030 (m), 959 (w), 903 (w), 841 (m), 806 (m),
746 (m), 724 (m), 698 (s), 623 (m), 615 (m), 583 (m) cmꢁ1. HRMS
(ESI): calcd for C33H43O3 [MþH]þ: 487.32067; found: 487.32048.
7.21 (m, 10H, CHAr), 10.79 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
d¼12.3, 13.1, 17.1, 20.1 (CH3), 18.9 (CH2CH3), 50.2 (CH), 60.4
(OCH2CH3), 111.3 (CAr), 124.8, 127.1, 128.1 (CHAr), 128.3, 132.1, 135.9,
141.5, 141.8 (CAr), 156.8 (COH), 171.1 (CO). IR (neat, cmꢁ1): 3083 (w),
3058 (w), 3022 (w), 2963 (w), 2929 (w), 2871 (w), 1726 (w), 1651
(s),1597 (m),1562 (m),1493 (m),1443 (m),1370 (m),1261 (m),1223
(m), 1188 (s), 1106 (m), 1033 (m), 805 (m), 743 (m), 726 (m), 698 (s),
622 (w), 599 (m), 584 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼388 (Mþ,
46), 343 (30), 342 (100), 341 (17), 314 (22), 299 (15), 251 (10), 236
(12),179 (12), 178 (11), 167 (56),166 (13), 165 (39), 152 (15), 115 (10),
91 (22), 77 (10), 43 (12). HRMS (ESI-Tof): calcd for C26H28O3
[MþH]þ: 388. 20384; found: 387.20297.
3.1.28. Methyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
benzoate (6k). Starting with 4b (0.564 g, 1.5 mmol) and 5a (0.429 g,
1.65 mmol), 6k was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a colourless oil (0.188 g, 33%). 1H NMR
(300 MHz, CDCl3):
OCH3), 5.84 (s, 1H, CH), 6.68 (s, 1H, CHAr), 6.86–6.99 (m, 8H, CHAr),
10.50 (s, 1H, OH). 13C NMR (CDCl3, 75 MHz):
d
¼1.98 (s, 3H, CH3), 2.05 (s, 3H, CH3), 3.82 (s, 3H,
3.1.25. Methyl 3-diphenylmethyl-5-butyl-6-hydroxy-2,4-dimethyl-
benzoate (6h). Starting with 4a (0.510 g,1.5 mmol) and 5h (0.521 g,
1.65 mmol), 6h was isolated after chromatography (silica gel, n-
heptane/EtOAc) as a colourless oil (0.277 g, 46%).1H NMR (300 MHz,
d
¼21.2, 22.6 (CH3), 49.3
(CH), 52.0 (OCH3), 112.9 (CAr), 115.1 (d, JC,F¼21.1 Hz, CHAr), 118.0
(CHAr), 130.5 (d, JC,F¼7.5 Hz, CHAr), 132.8 (CAr), 137.5 (d, JC,F¼3.5 Hz,
CAr), 140.1, 145.0 (CAr), 160.0 (COH), 161.2 (d, JC,F¼245.0 Hz, CAr), 171.8
CDCl3):
d
¼0.75 (t, J¼6.9 Hz, 3H, (CH2)2(CH2)CH3), 1.21–1.31 (m, 4H,
2ꢂCH2), 1.84 (s, 3H, CH3), 1.95 (s, 3H, CH3), 2.49 (t, J¼7.1 Hz,
(CO). 19F NMR (282 MHz, CDCl3):
d
¼ꢁ116.8. IR (neat, cmꢁ1): 2949
CH2(CH2)2CH3), 3.69 (s, 3H, OCH3), 5.89 (s, 1H, CH), 6.90–7.09 (m,
(w), 2918 (w), 2850 (w), 1650 (s), 1661 (m), 1573 (m), 1503 (s), 1468
(m), 1440 (m), 1349 (m), 1299 (m), 1229 (s), 1155 (m), 1072 (m), 955
(m), 865 (m), 830 (m), 795 (m), 724 (m) 648 (m), 609 (m), 555 (m),
529 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼382 (Mþ, 57), 351 (35), 350
(100), 335 (30), 321 (15), 255 (18), 203 (18), 202 (15), 201 (28), 184
(10), 183 (24). HRMS (EI): calcd for C23H20O3F2 [M]þ: 382.13750;
found: 382.137228.
10H, CHAr), 10.62 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
d¼15.1, 19.5,
22.4 (CH3), 24.2, 27.7, 30.8 (CH2), 52.3 (CH), 53.1 (OCH3), 113.3 (CAr),
127.0,129.3, 130.3 (CHAr), 130.6, 134.3, 138.0,143.6, 144.3 (CAr), 159.1
(COH), 173.8 (CO). IR (neat, cmꢁ1): 3083 (w), 3058 (w), 3022 (w),
2952, 2870 (w), 2855 (w),1737 (w),1655 (s),1596 (w),1493 (w),1437
(s), 1348 (w), 1313 (w), 1231 (w), 1200 (s), 1115 (w), 1044 (w), 1022
(w), 965 (w), 842 (w), 805 (w), 746 (w), 725 (w), 697 (s), 582 (w)
cmꢁ1. MS (EI, 70 eV): m/z (%)¼402 (Mþ, 100), 371 (26), 370 (83), 369
(12), 355 (24), 353 (22), 342 (15), 341 (14), 328 (37), 327 (25), 285
(10), 279 (16),167 (15),165 (14). HRMS (EI): calcd for C27H30O3 [M]þ:
402.21895; found: 402.218714.
3.1.29. Ethyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
benzoate (6l). Starting with 4b (0.564 g, 1.5 mmol) and 5b (0.452 g,
1.65 mmol), 6l was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a solid (0.220 g, 37%), mp 76–77 ꢀC. 1H NMR
(300 MHz, CDCl3):
d
¼1.28 (t, J¼7.1 Hz, 3H, OCH2CH3), 1.97 (s, 3H,
3.1.26. Methyl 3-diphenylmethyl-6-hydroxy-2,4-dimethyl-5-octylben-
zoate (6i). Starting with 4a (0.510 g, 1.5 mmol) and 5i (0.614 g,
1.65 mmol), 6i was isolated after chromatography (silica gel, n-
heptane/EtOAc) as a as a colourless oil (0.343 g, 50%). 1H NMR
CH3), 2.07 (s, 3H, CH3), 4.30 (t, J¼7.1 Hz, 2H, OCH2CH3), 5.84 (s, 1H,
CH), 6.65 (s, 1H, CHAr), 6.85–7.18 (m, 8H, CHAr), 10.59 (s, 1H, OH).
13C NMR (CDCl3, 75 MHz):
d
¼14.1, 21.2, 22.7 (CH3), 49.3 (CH), 61.6
(OCH2CH3), 113.0 (CAr), 115.0 (d, JC,F¼21.1 Hz, CHAr), 118.0 (CHAr),
130.3 (d, JC,F¼7.5 Hz, CHAr), 132.7 (CAr), 137.6 (d, JC,F¼3.1 Hz, CAr),
140.1, 145.0 (CAr), 160.0 (COH), 161.1 (d, JC,F¼245.0 Hz, CAr), 171.3
(300 MHz, CDCl3):
d
¼0.70 (t, J¼7.1 Hz, 3H, (CH2)6(CH2)CH3), 1.05–
1.08 (m, 10H, 5ꢂCH2), 1.24–1.29 (m, 2H, CH2), 1.84 (s, 3H, CH3), 1.95
(s, 3H, CH3), 2.48 (t, J¼7.2 Hz, 2H, CH2(CH2)(CH2)5CH3), 3.70 (s, 3H,
OCH3), 5.89 (s, 1H, CH), 6.90–7.12 (m, 10H, CHAr), 10.61 (s, 1H, OH).
(CO). 19F NMR (282 MHz, CDCl3):
d
¼ꢁ116.8. IR (neat, cmꢁ1): 3039
(w), 2994 (w), 2954 (w), 2922 (w), 2851 (w), 1727 (w), 1650 (s),
1598 (m), 1536 (m), 1503 (s), 1463 (m), 1393 (m), 1333 (m), 1292
(m), 1268 (m), 1220 (s), 1210 (s), 1157 (m), 1074 (m), 1013 (m), 863
13C NMR (CDCl3, 62 MHz):
d¼15.2, 19.5, 22.4 (CH3), 27.9, 30.3, 30.4,
30.5, 30.6, 31.2, 33.0 (CH2), 52.3 (s, 1H, CH), 53.1 (OCH3), 113.3 (CAr),
127.0, 129.3 (CHAr), 130.0 (CAr), 130.3 (CHAr), 134.3, 138.0, 143.6,
144.3 (CAr), 159.0 (COH), 173.8 (CO). IR (neat, cmꢁ1): 3082 (w), 3059
(w), 3023 (w), 2952 (m), 2922 (m), 2852 (m), 1933 (w), 1701 (w),
1657 (s), 1597 (m), 1493 (m), 1437 (s), 1350 (w), 1292 (m), 1245 (m),
1200 (s), 1119 (m), 1048 (m), 1029 (m), 965 (w), 919 (w), 841 (m),
806 (m), 746 (m), 724 (m), 697 (s), 623 (m), 583 (m) cmꢁ1. MS (EI,
70 eV): m/z (%)¼458 (Mþ, 84), 427 (33), 426 (100), 425 (16), 411
(19), 409 (26), 370 (10), 369 (29), 355 (14), 341 (22), 336 (16), 335
(76), 329 (14), 328 (67), 327 (44), 301 (12), 300 (28), 299 (10), 285
(23), 251 (10), 249 (11), 223 (16), 222 (14), 221 (11), 209 (14), 179
(15),178 (18),168 (11),167 (65),166 (15),165 (37),152 (13),105 (10),
91 (30), 41 (10). HRMS (EI): calcd for C31H38O3 [M]þ: 458.28155;
found: 458.281976.
(m), 829 (m), 794 (m), 723 (m) 640 (m), 592 (m), 528 (m) cmꢁ1
.
MS (EI, 70 eV): m/z (%)¼396 (Mþ, 45), 351 (32), 350 (100), 335
(20), 321 (12), 255 (13), 203 (16), 202 (12), 201 (20), 183 (20).
HRMS (EI): calcd for C24H22O3F2 [M]þ: 396.15315; found:
396.153067.
3.1.30. Benzyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
benzoate (6m). Starting with 4b (0.564 g, 1.5 mmol) and 5c
(0.555 g, 1.65 mmol), 6m was isolated after chromatography
(silica gel, n-heptane/EtOAc) as a colourless solid (0.466 g, 68%),
mp 112–113 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼1.99 (s, 3H, CH3),
2.12 (s, 3H, CH3), 5.33 (s, 2H, OCH2), 5.87 (s, 1H, CHAr), 6.70 (s, 1H,
CHAr), 6.89–7.01 (m, 8H, CHAr), 7.30–7.37 (m, 5H, CHAr), 10.56 (s,
1H, OH). 13C NMR (CDCl3, 62 MHz):
d
¼21.3, 22.7 (CH3), 49.3 (CH),
3.1.27. Methyl 3-diphenylmethyl-5-decyl-6-hydroxy-2,4-dimethyl-
benzoate (6j). Starting with 4a (0.510 g, 1.5 mmol) and 5j (0.661 g,
1.65 mmol), 6j was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a colourless oil (0.415 g, 57%). 1H NMR
67.4 (OCH2), 112.8 (CAr), 114.6 (d, JC,F¼21.2 Hz, CHAr), 118.5 (CHAr),
128.5 (d, JC,F¼7.7 Hz, CHAr), 128.6 (CAr), 137.5 (d, JC,F¼3.1 Hz, CAr),
140.2, 145.2 (CAr), 160.1 (COH), 161.1 (d, JC,F¼245.1 Hz, CAr), 171.1
(CO). 19F NMR (282 MHz, CDCl3):
d
¼ꢁ116.8. IR (neat, cmꢁ1): 3070
(300 MHz, CDCl3):
d
¼0.70 (t, J¼6.8 Hz, 3H, (CH2)8CH2CH3),1.07–1.12
(w), 3035 (w), 2979 (w), 2931 (w), 2884 (w), 1649 (s), 1598 (m),
1574 (m), 1500 (s), 1426 (m), 1381 (m), 1316 (m), 1292 (m), 1217
(s), 1175 (s), 1145 (m), 1067 (m), 1029 (m), 1012 (m), 953 (m), 860
(m), 829 (m), 817 (m), 794 (s), 748 (s), 698 (s), 647 (m), 598 (m),
528 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼458 (Mþ, 18), 350 (34), 91
(m,14H, 7ꢂCH2),1.24–1.29 (m, 2H, CH2),1.84 (s, 3H, CH3),1.95 (s, 3H,
CH3), 2.48 (t, J¼7.2 Hz, 2H, CH2(CH2)8CH3), 3.70 (s, 3H, OCH3), 5.89 (s,
1H, CH), 6.90–7.09 (m, 10H, CHAr), 10.61 (s, 1H, OH). 13C NMR (CDCl3,
62 MHz):
d
¼15.2, 19.5, 22.4 (CH3), 23.8, 27.9, 30.3, 30.5, 30.6, 30.8,

R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
1649
(100). HRMS (ESI): calcd for C29H25O3F2 [MþH]þ: 459.17663;
MS (EI, 70 eV): m/z (%)¼438 (Mþ 100), 407 (28), 406 (72), 389 (24),
378 (18), 377 (16), 365 (10), 364 (40), 363 (28), 321 (13), 297 (15),
203 (21), 201 (12), 183 (14), 109 (12). HRMS (ESI): calcd for
C27H29O3F2 [MþH]þ: 439.20065; found: 439.20975.
found: 459.17593.
3.1.31. Ethyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4,5-trimethyl-
benzoate (6n). Starting with 4b (0.564 g, 1.5 mmol) and 5e (0.476 g,
1.65 mmol), 6n was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a solid (0.239 g, 39%), mp 63–64 ꢀC. 1H NMR
3.1.34. Methyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
5-nonylbenzoate (6q). Starting with 4b (0.564 g, 1.5 mmol) and 5k
(0.614 g, 1.65 mmol), 6q was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a solid (0.402 g, 53%), mp 147–148 ꢀC. 1H
(300 MHz, CDCl3):
d
¼1.29 (t, J¼7.1 Hz, 3H, OCH2CH3), 1.88 (s, 3H,
CH3), 2.10 (s, 6H, 2ꢂCH3), 4.32 (q,J¼7.1 Hz, 2H, OCH2CH3), 5.90 (s,
1H, CH), 6.86–6.99 (m, 8H, CHAr), 10.83 (s, 1H, OH). 13C NMR
NMR (300 MHz, CDCl3):
d
¼0.70 (t, J¼7.0 Hz, 3H, (CH2)7CH2CH3),
(CDCl3, 75 MHz):
d
¼12.2, 14.1, 19.0, 21.0 (CH3), 49.7 (OCH3), 61.5
1.09–1.16 (m, 12H, 6ꢂCH2), 1.27–1.31 (m, 2H, CH2), 1.82 (s, 3H, CH3),
1.92 (s, 3H, CH3), 2.48 (t, J¼7.1 Hz, 2H, CH2(CH2)7CH3), 3.71 (s, 3H,
OCH3), 5.79 (s, 1H, CH), 6.75–6.88 (m, 8H, CHAr), 10.67 (s, 1H, OH).
(OCH2CH3), 112.3 (CAr), 115.0 (d, JC,F¼21.0 Hz, CHAr), 123.5 (CAr),
130.4 (d, JC,F¼7.8 Hz, CHAr), 132.5, 136.5 (CAr), 137.5 (d, JC,F¼3.2 Hz,
CAr), 143.2 (CAr), 159.5 (COH), 160.4 (d, JC,F¼244.6 Hz, CAr), 172.0
13C NMR (CDCl3, 75 MHz):
d
¼15.2, 23.8, 27.9 (CH3) 28.3, 30.3, 30.5,
(CO). 19F NMR (282 MHz, CDCl3):
d
¼ꢁ117.0. IR (neat, cmꢁ1): 3070
30.7, 30.8, 30.9, 31.2, 33.0 (CH2), 51.0 (CH), 53.2 (OCH3), 113.5 (CAr),
116.1 (d, JC,F¼21.2 Hz, CHAr), 129.6 (CAr), 131.5 (d, JC,F¼7.7 Hz, CHAr),
133.9, 137.8 (CAr), 139.1 (d, JC,F¼3.4 Hz, CAr), 143.9 (CAr), 159.2 (COH),
162.3 (d, JC,F¼244.7 Hz, CPh), 173.6 (CO). 19F NMR (282 MHz, CDCl3):
(w), 3035 (w), 2979 (w), 2931 (w), 2884 (w), 1649 (s), 1598 (m),
1574 (m), 1500 (s), 1426 (m), 1381 (m), 1316 (m), 1292 (m), 1217 (s),
1175 (s), 1145 (m), 1067 (m), 1029 (m), 1012 (m), 953 (m), 860 (m),
829 (m), 817 (m), 794 (s), 748 (s), 698 (s), 647 (m), 598 (m), 528
(m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼410 (Mþ, 30), 365 (29), 364
(100), 336 (22), 321 (28), 241 (18), 240 (10), 203 (26), 202 (11), 201
(25), 197 (11), 196 (11), 183 (32), 109 (16), 91 (14), 44 (21), 43 (18).
HRMS (ESI): calcd for C25H24O3F2 [M]þ: 410.16880; found:
410.169602.
d
¼ꢁ117.1. IR (neat, cmꢁ1): 2952 (w), 2922 (w), 2853 (w), 1751 (m),
1654 (m), 1558 (s), 1506 (m), 1446 (m), 1351 (m), 1227 (s), 1157 (s),
1148 (m), 1030 (m), 1016 (m), 841 (m), 798 (m), 778 (m), 721 (m),
667 (m), 628 (w), 568 (m), 530 (m) cmꢁ1. MS (EI, 70 eV): m/z
(%)¼508 (Mþ 100), 473 (18), 405 (16), 381 (20), 377 (18), 365 (19),
364 (51), 336 (14), 276 (13), 275 (76), 183 (10), 109 (16), 57 (13), 43
(14). HRMS (ESI): calcd for C32H38F2O3 [MþH]þ: 509.2789; found:
509.2787.
3.1.32. Methyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
5-ethylbenzoate (6o). Starting with 4b (0.564 g, 1.5 mmol) and 5f
(0.476 g, 1.65 mmol), 6o was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a yellowish solid (0.251 g, 41%), mp
3.1.35. Methyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
5-decylbenzoate (6r). Starting with 4b (0.564 g, 1.5 mmol) and 5j
(0.661 g, 1.65 mmol), 6r was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a yellowish solid (0.429 g, 55%), mp 161–
82–83 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼1.03 (t, J¼7.4 Hz, 3H,
CH2CH3), 1.94 (s, 3H, CH3), 2.03 (s, 3H, CH3), 2.63 (q, J¼7.4 Hz, 2H,
CH2CH3), 3.82 (s, 3H, OCH3), 5.90 (s, 1H, CH), 6.86–6.99 (m, 8H,
162 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼0.75 (t, J¼6.8 Hz, 3H,
CHAr), 10.73 (s, 1H, OH). 13C NMR (CDCl3, 75 MHz):
d
¼12.3, 16.9,
(CH2)8CH2CH3), 1.08–1.12 (m, 14H, 7ꢂCH2), 1.17–1.25 (m, 2H, CH2),
1.82 (s, 3H, CH3), 1.92 (s, 3H, CH3), 2.48 (t, 3J¼7.2 Hz, 2H,
CH2(CH2)8CH3), 3.71 (s, 3H, OCH3), 5.78 (s, 1H, CHAr), 6.76–6.89 (m,
18.9 (CH3), 20.2 (CH2CH3), 48.8 (CH), 51.0 (OCH3), 111.3 (CAr), 114.0
(d, JC,F¼21.2 Hz, CHAr), 128.5 (CAr), 129.4 (d, JC,F¼7.7 Hz, CHAr),
131.7, 135.7 (CAr), 136.8 (d, JC,F¼3.2 Hz, CAr), 141.6 (CAr), 156.9
(COH), 161.1 (d, JC,F¼244.7 Hz, CAr), 171.4 (CO). 19F NMR (282 MHz,
8H, CHAr), 10.61 (s, 1H, OH). 13C NMR (CDCl3, 75 MHz):
d
¼15.2,
19.4, 22.4 (CH3), 23.8, 27.9, 28.3, 30.3, 30.5, 30.7, 30.8, 31.2, 33.0
(CH2), 51.0 (CH), 53.2 (OCH3), 113.5 (CAr), 116.1 (d, JC,F¼21.1 Hz,
CHAr), 129.6 (CAr), 131.5 (d, JC,F¼8.2 Hz, CHAr), 133.9, 137.8 (CAr),
139.1 (d, JC,F¼3.0 Hz, CAr), 144.0 (CAr), 159.2 (COH), 162.3 (d,
JC,F¼245.0 Hz, CAr), 173.6 (CO). 19F NMR (282 MHz, CDCl3):
CDCl3):
d
¼ꢁ117.0. IR (neat, cmꢁ1): 2961 (w), 2929 (w), 2873 (w),
2852 (w), 1732 (w), 1656 (s), 1599 (m), 1563 (w), 1504 (s), 1439
(m), 1398 (m), 1350 (m), 1293 (m), 1258 (s), 1223 (m), 1201 (m),
1157 (s), 1096 (m), 1014 (s), 953 (m), 861 (m), 832 (m), 795 (s),
699 (s), 643 (m), 601 (w), 567 (m), 530 (m) cmꢁ1. MS (EI, 70 eV):
m/z (%)¼410 (Mþ, 46), 380 (10), 379 (32), 378 (100), 377 (16), 363
(14), 353 (21), 352 (67), 351 (10), 350 (31), 338 (24), 337 (86), 336
(12), 335 (25), 324 (16), 323 (45), 321 (18), 257 (14), 241 (12), 227
(17), 226 (14), 203 (15), 202 (20), 201 (24), 196 (15), 189 (10), 183
(25), 109 (12). HRMS (EI): calcd for C25H24O3F2 [M]þ: 410.16880;
found: 410.169602.
d
¼ꢁ117.0. IR (neat, cmꢁ1): 2952 (w), 2922 (w), 2853 (w), 1751 (m),
1658 (m), 1600 (m), 1505 (s), 1437 (m), 1399 (m), 1351 (m), 1294
(m), 1225 (s), 1201 (m), 1157 (s), 1120 (m), 1048 (m), 1015 (m), 907
(m), 840 (m), 797 (s), 733 (m), 671 (m), 628 (m), 568 (s), 530 (m)
cmꢁ1. MS (EI, 70 eV): m/z (%)¼522 (100) (Mþ 100), 490 (83), 473
(17), 405 (15), 381 (23), 377 (14), 365 (11), 364 (51), 363 (34), 336
(13), 321 (11), 276 (12), 275 (80), 203 (59), 201 (10), 183 (11), 109
(14), 57 (10), 43 (13). HRMS (ESI): calcd for C33H41O3F2 [MþH]þ:
523.29465; found: 522.29452.
3.1.33. Methyl 3-(bis(4-fluorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
5-butylbenzoate (6p). Starting with 4b (0.564 g, 1.5 mmol) and 5 h
(0.521 g, 1.65 mmol), 6p was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a solid (0.348 g, 53%), mp 116–117 ꢀC. 1H
3.1.36. Methyl 3-(bis(4-chlorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
benzoate (6s). Starting with 4c (0.614 g, 1.5 mmol) and 5a (0.429 g,
1.65 mmol), 6s was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a solid (0.311 g, 50%), mp 95–97 ꢀC. 1H NMR
NMR (300 MHz, CDCl3):
d
¼0.75 (t, J¼6.9 Hz, 3H, (CH2)2CH2CH3),
1.21–1.28 (m, 4H, 2ꢂCH2), 1.83 (s, 3H, CH3), 1.92 (s, 3H, CH3), 2.49 (t,
J¼7.3 Hz, 2H, CH2(CH2)2CH3), 3.71 (s, 3H, OCH3), 5.79 (s, 1H, CH),
6.75–6.88 (m, 8H, CHAr), 10.62 (s, 1H, OH). 13C NMR (CDCl3,
(300 MHz, CDCl3):
OCH3), 5.82 (s, 1H, CH), 6.66 (s, 1H, CHAr), 6.90–7.19 (m, 8H, CHAr),
10.53 (s, 1H, OH). 13C NMR (CDCl3, 75 MHz):
¼20.4, 21.6 (CH3), 48.6
d
¼1.98 (s, 3H, CH3), 2.03 (s, 3H, CH3), 3.81 (s, 3H,
75 MHz):
d
¼15.2, 18.2, 21.2 (CH3), 23.1, 26.5, 31.3 (CH2), 49.8 (CH),
d
52.08 (OCH3), 113.5 (CAr), 116.1 (d, JC,F¼21.2 Hz, CHAr), 129.6 (CAr),
131.5 (d, JC,F¼7.7 Hz, CHAr), 133.9, 137.8 (CAr), 139.1 (d, JC,F¼3.2 Hz,
(CH), 51.0 (OCH3), 111.9 (CAr), 117.0, 127.4, 129.3 (CHAr), 131.0, 131.2,
139.1, 139.2, 144.0 (CAr), 159.0 (COH), 170.7 (CO). IR (neat, cmꢁ1):
2961 (w), 2918 (w), 1663 (s), 1599 (m), 1564 (m), 1492 (m), 1435
(m), 1341 (m), 1265 (m), 1210 (m), 1143 (m), 1069 (m), 942 (m), 914
(w), 857 (m), 801 (m), 736 (m), 719 (s) 696 (s), 613 (m), 571 (m)
cmꢁ1. MS (EI, 70 eV): m/z (%)¼415 (Mþ, 17), 414 (78), 386 (17), 385
(28), 384 (93), 383 (48), 382 (100), 369 (10), 367 (15), 347 (22), 319
(12), 271 (21), 239 (10), 237 (12), 235 (28), 201 (10), 199 (31), 179
1
CPh), 144.0 (CAr), 159.2 (COH), 162.3 (d, JC,F¼244.7 Hz, CAr), 173.6
(CO). 19F NMR (282 MHz, CDCl3):
d
¼ꢁ117.0. IR (neat, cmꢁ1): 3034
(w), 2954 (w), 2927 (w), 2871 (w), 2858 (w), 1737 (m), 1655 (m),
1504 (s), 1438 (m), 1397 (m), 1350 (m), 1293 (m), 1223 (s), 1200 (s),
1157 (s), 1115 (m), 1044 (m), 1015 (m), 881 (m), 832 (m), 807 (m),
796 (s), 731 (s), 670 (m), 639 (m), 603 (m), 567 (s), 529 (m) cmꢁ1
.

1650
R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
(14), 178 (11), 165 (50). HRMS (ESI): calcd for C23H19Cl2O3 [MꢁH]þ:
(s, 3H, CH3), 1.99 (s, 3H, CH3), 2.00 (s, 3H, CH3), 4.22 (q, J¼7.1 Hz, 2H,
OCH2CH3), 5.78 (s, 1H, CH), 6.82–6.85 (m, 4H, CHAr), 7.06–7.09 (m,
413.07188; found: 413.07167.
4H, CHAr), 10.77 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
d¼12.2, 14.1,
3.1.37. Ethyl 3-(bis(4-chlorophenyl)methyl)-6-hydroxy-2,4-dimethy-
lbenzoate (6t). Starting with 4c (0.614 g, 1.5 mmol) and 5b (0.452 g,
1.65 mmol), 6t was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a white solid (0.340 g, 53%), mp 117–118 ꢀC. 1H
19.0, 21.0 (CH3), 50.0 (CH), 61.6 (OCH2CH3), 112.3, 123.6 (CAr), 128.4,
130.3 (CHAr), 131.8, 136.5, 139.5, 140.5, 143.2 (CAr), 158.1 (COH), 171.9
(CO). IR (neat, cmꢁ1): 3070 (w), 3035 (w), 2979 (w), 2931 (w), 2884
(w), 1649 (s), 1598 (m), 1574 (m), 1500 (s), 1426 (m), 1381 (m), 1316
(m), 1292 (m), 1217 (s), 1175 (s), 1145 (m), 1067 (m), 1029 (m), 1012
(m), 953 (m), 860 (m), 829 (m), 817 (m), 794 (s), 748 (s), 698 (s), 647
(m), 598 (m), 528 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼442 (Mþ, 10),
414 (13), 413 (21), 412 (63), 411 (30), 410 (100), 384 (16), 382 (28),
367 (13), 285 (12), 285 (12), 165 (15), 71 (11), 69 (12), 57 (14), 57
(11), 43 (16). HRMS (ESI): calcd for C25H23 Cl2O3 [MꢁH]þ:
441.10297; found: 441.10289.
NMR (300 MHz, CDCl3):
d
¼1.29 (t, J¼7.1 Hz, 3H, OCH2CH3), 1.97 (s,
3H, CH3), 2.06 (s, 3H, CH3), 4.31 (q, J¼7.1 Hz, 2H, OCH2CH3), 5.82 (s,
1H, CH), 6.66 (s, 1H, CHAr), 6.91–6.94 (m, 4H, CHAr), 7.16–7.19 (m,
4H, CHAr), 10.63 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
d¼13.1, 20.3,
21.7 (CH3), 48.6 (CH), 55.6 (OCH3), 60.6 (OCH2CH3),112.0 (CAr),117.0,
127.4, 129.0 (CHAr), 129.3 131.0, 131.1 (CAr), 139.2, 143.9 (CAr), 159.2
(COH), 170.3 (CO). IR (neat, cmꢁ1): 2981 (w), 2958 (w), 2923 (w),
2852 (w), 1647 (s), 1596 (m), 1572 (m), 1487 (s), 1463 (m), 1395 (m),
1371 (m), 1321 (m), 1292 (m), 1224 (s), 1178 (m), 1143 (m), 1089 (s),
1067 (m), 1009 (s), 861 (m), 815 (m), 784 (m), 734 (m), 686 (m), 627
(m), 593 (m), 583 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼429 (Mþ, 10),
428 (38), 386 (12), 385 (20), 384 (67), 383 (32), 382 (100), 367 (10),
347 (19), 239 (10), 237 (11), 236 (10), 235 (23), 201 (12), 199 (31),
180 (10), 179 (16), 178 (13), 166 (11), 165 (57), 164 (10), 156 (10), 125
(11), 91 (12), 77 (10), 67 (10), 36 (12). HRMS (ESI): calcd for
C24H22Cl2O3 [MꢁH]þ: 428.08732; found: 428.08796.
3.1.41. Methyl 3-(bis(4-chlorophenyl)methyl)-5-ethyl-6-hydroxy-2,4-
dimethylbenzoate (6x). Starting with 4c (0.614 g, 1.5 mmol) and 5f
(0.476 g, 1.65 mmol), 6x was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a yellowish solid (0.278 g, 42%), mp
127–128 ꢀC. 1H NMR (300 MHz, CDCl3):
OCH2CH3), 1.94 (s, 3H, CH3), 2.01 (s, 3H, CH3), 2.63 (q, J¼7.4 Hz, 2H,
OCH2CH3), 3.82 (s, 3H, OCH3), 5.88 (s, 1H, CH), 6.92–6.95 (m, 4H,
CHAr), 7.16–7.19, (m, 4H, CHAr), 10.77 (s, 1H, OH). 13C NMR (CDCl3,
d
¼1.02 (t, J¼7.4 Hz, 3H,
75 MHz):
d
¼12.3, 17.0, 19.0, 20.3 (CH3), 28.6 (CH2), 49.1 (CH), 51.1
3.1.38. Benzyl 3-(bis(4-chlorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
benzoate (6u). Starting with 4c (0.614 g, 1.5 mmol) and 5c (0.429 g,
1.65 mmol), 6u was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a solid (0.507 g, 69%), mp 137–138 ꢀC. 1H NMR
(OCH3), 111.3 (CAr), 127.4 (CHAr), 128.6 (CAr), 129.3 (CHAr), 130.8,
131.1, 135.7, 139.5, 141.5 (CAr), 157.0 (COH), 171.4 (CO). IR (neat,
cmꢁ1): 2953, 2927 (w), 2871 (w), 2854 (w), 1731 (w), 1656 (s), 1593
(m), 1561 (m), 1489 (s), 1439 (m), 1350 (m), 1324 (m), 1290 (m),
1223 (m), 1178 (m), 1106 (m), 1091 (m), 1013 (s), 877 (w), 807 (m),
781 (m), 705 (m), 653 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼443 (Mþ,
10), 442 (42), 414 (10), 413 (17), 412 (63), 411 (31), 410 (100), 384
(17), 382 (27), 367 (12), 285 (13), 285 (13), 165 (14), 71 (10), 69 (10),
57 (16), 57 (10), 43 (17). HRMS (EI): calcd for C25H24Cl2O3 [MþH]þ:
444.18023; found: 444.18011.
(300 MHz, CDCl3):
d
¼1.95 (s, 3H, CH3), 2.05 (s, 3H, CH3), 5.28 (s, 2H,
OCH2), 5.80 (s, 1H, CH), 6.66 (CHAr), 6.89–6.93 (m, 4H, CHAr), 7.14–
7.18 (m, 4H, CHAr), 7.26–7.31 (m, 5H, CH), 10.54 (s, 1H, OH). 13C NMR
(CDCl3, 62 MHz):
d
¼21.4, 22.8 (CH3), 49.6 (CH), 67.4 (OCH2), 112.8
(CAr), 118.1, 128.2, 128.4, 128.6, 128.7, 130.3 (CHAr), 132.0, 133.2,
135.0, 140.1, 140.2, 145.2 (CAr), 160.2 (COH), 171.1 (CO). IR (neat,
cmꢁ1): 3031 (w), 2979 (w), 2928 (w), 1660 (s), 1598 (m), 1567 (m),
1487 (m), 1462 (m), 1387 (m), 1341 (m), 1270 (m), 1257 (m), 1231
(m), 1208 (m), 1144 (m), 1089 (m), 1068 (s), 1012 (m), 949 (w), 838
3.1.42. Methyl 3-(bis(4-chlorophenyl)methyl)-6-hydroxy-2,4-dimethyl-
5-pentylbenzoate (6y). Starting with 4c (0.614 g, 1.5 mmol) and 5l
(0.545 g, 1.65 mmol), 6y was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a yellowish solid (0.385 g, 53%), mp
(m), 801 (m), 749 (m), 737 (m), 693 (s), 636 (m), 583, 539 (m) cmꢁ1
.
MS (EI, 70 eV): m/z (%)¼490 (Mþ, 60), 401 (10), 399 (16), 385 (15),
384 (75), 383 (28), 382 (100), 165 (15), 92 (22), 91 (40), 57 (13), 54
(16), 43 (11). HRMS (EI): calcd for C29H25Cl2O3 [MþH]þ: 491.11996;
found: 491.11201.
131–132 ꢀC. 1H NMR (300 MHz, CDCl3):
d
¼0.86 (t, J¼6.9 Hz, 3H,
(CH2)4CH3), 1.18–1.23 (m, 4H, 2ꢂCH2), 1.31–1.38 (m, 2H, CH2), 1.93
(s, 3H, CH3), 2.01 (s, 3H, CH3), 2.59 (t, J¼7.3 Hz, 2H, CH2(CH2)3CH3),
3.82 (s, 3H, OCH3), 5.87 (s, 1H, CH), 6.91–6.94 (m, 4H, CHAr), 7.16–
7.19 (m, 4H, CHAr), 10.75 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
3.1.39. Methyl 3-(bis(4-chlorophenyl)methyl)-6-hydroxy-2,4,5-tri-
methylbenzoate (6v). Starting with 4c (0.614 g, 1.5 mmol) and 5d
(0.452 g, 1.65 mmol), 6v was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a yellowish solid (0.255 g, 40%), mp
113–114 ꢀC. 1H NMR (300 MHz, CDCl3): 1.89 (s, 3H, CH3), 2.06
(s, 3H, CH3), 2.10 (s, 3H, CH3), 3.83 (s, 3H, OCH3), 5.88 (s, 1H, CH),
6.92–6.95 (m, 4H, CHAr), 7.16–7.19 (m, 4H, CHAr), 10.81 (s, 1H, OH).
d
¼12.9, 13.1, 17.2 (CH3), 20.3, 21.6, 22.0, 25.5, 28.6 (CH2), 49.1 (s, 1H,
CH), 51.0 (OCH3), 111.2, 127.3 (CAr), 127.4, 129.3 (CHAr), 130.8, 131.1,
135.7, 139.5, 141.7, 144.3 (CAr), 157.2 (COH), 171.4 (CO). IR (neat,
cmꢁ1): 3059 (w), 3023 (w), 2952 (m), 2922 (m), 2852 (m), 1933 (w),
1701 (w), 1657 (s), 1597 (m), 1493 (m), 1437 (s), 1350 (w), 1292 (m),
1245 (m), 1200 (s), 1119 (m), 1048 (m), 1029 (m), 965 (w), 919 (w),
13C NMR (CDCl3, 62 MHz):
d
¼13.0, 21.6, 28.6 (CH3), 49.0 (CH), 51.1
841 (m), 806 (m), 746 (m), 724 (m), 697 (s), 623 (m), 583 (m) cmꢁ1
.
(OCH3), 111.2, 116.4 (CAr), 127.4, 129.3, 130.8 (CHAr), 134.0, 137.9,
143.6, 144.7 (CAr), 159.0 (COH), 173.3 (CO). IR (neat, cmꢁ1): 2921
(w), 2852 (w), 1731 (w), 1659 (s), 1592 (m), 1565 (m), 1489 (m),
1456 (m), 1439 (m), 1398 (m), 1377 (m), 1347 (m), 1280 (m), 1260
(m), 1201 (m), 1164 (m), 1091 (m), 1013 (m), 925 (w), 822 (m),
756 (w), 698 (m), 596 (m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼429 (10),
428 (38), 400 (10), 399 (15), 398 (62), 397 (26), 396 (100), 199
(11), 57(32). HRMS (ESI): calcd for C24H22Cl2O3 [MꢁH]þ:
427.08732; found: 427.08657.
MS (EI, 70 eV): m/z (%)¼484 (100), 439 (17), 423 (11), 411 (15), 409
(12), 399 (33) 398 (48) 397 (10), 396 (36), 395 (20), 368 (15), 355
(17), 285 (14), 257 (18), 235 (30), 201 (15), 199 (14), 166 (12), 165
(32), 139 (14), 127 (12), 97 (17), 95 (10), 85 (15), 71 (19), 67 (22), 57
(37), 56 (10), 43 (30). HRMS (EI): calcd for C28H30Cl2O3 [MþH]þ:
485.15723; found: 485.12623.
3.1.43. Methyl 3-(bis(4-chlorophenyl)methyl)-5-decyl-6-hydroxy-2,4-
dimethylbenzoate (6z). Starting with 4c (0.614 g, 1.5 mmol) and 5j
(0.661 g, 1.65 mmol), 6z was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a solid (0.474 g, 57%), mp 141–142 ꢀC. 1H
3.1.40. Ethyl 3-(bis(4-chlorophenyl)methyl)-6-hydroxy-2,4,5-trimethyl-
benzoate (6w). Starting with 4c (0.614 g, 1.5 mmol) and 5e (0.476 g,
1.65 mmol), 6w was isolated after chromatography (silica gel, n-
heptane/EtOAc) as a yellowish solid (0.285 g, 43%), mp 111–112 ꢀC.
NMR (300 MHz, CDCl3):
d
¼0.70 (t, J¼6.9 Hz, 3H, CH2(CH2)8CH3),
1.03–1.08 (m, 14H, 7ꢂCH2), 1.23–1.30 (m, 2H, CH2), 1.82 (s, 3H, CH3),
1.91 (s, 3H, CH3), 2.48 (t, J¼7.0 Hz, 2H, CH2(CH2)8CH3), 3.71 (s, 3H,
OCH3), 5.77 (s, 1H, CH), 6.81–6.84 (m, 4H, CHAr), 7.05–7.08 (m, 4H,
1H NMR (300 MHz, CDCl3):
d¼1.19 (t, J¼7.1 Hz, 3H, OCH2CH3), 1.78

R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
1651
(CHAr)), 10.65 (s, 1H, OH). 13C NMR (CDCl3, 62 MHz):
d
¼15.2, 19.4,
165 (21). HRMS (EI): calcd for C18H20O3 [M]þ: 284.14070; found:
284.140521.
22.5 (CH3), 23.8, 28.0, 28.3, 30.3, 30.5, 31.2 (CH2), 51.3 (CH), 53.2
(OCH3), 113.5 (CAr), 129.6, 131.5 (CHAr), 133.0, 133.3, 137.8, 141.7,
144.0 (CAr), 159.3 (COH), 173.6 (CO). IR (neat, cmꢁ1): 2952 (m), 2922
(s), 2852 (m), 1933 (w), 1745 (m), 1702 (m), 1658 (s), 1594 (m), 1562
(m), 1489 (m), 1455 (m), 1437 (m), 1377 (w), 1323 (m), 1278 (m),
1244 (m), 1235 (s), 1201 (m), 1178 (m), 1120 (w), 1091 (m), 1013 (m),
3.1.47. Benzyl 3-(1-(4-bromophenyl)ethyl)-6-hydroxy-2,4-dimethyl-
benzoate (6ad). Starting with 4f (0.535 g, 1.5 mmol) and 5c (0.429 g,
1.65 mmol), 6ad was isolated after chromatography (silica gel, n-
heptane/EtOAc) as a solid (0.475 g, 72%), mp 147–148 ꢀC. 1H NMR
(300 MHz, CDCl3): 1.53 (d, J¼7.2 Hz, 3H, CH3), 2.10 (s, 3H, CH3), 2.12 (s,
3H, CH3), 4.45 (q, J¼7.2 Hz, 1H, CH), 5.28 (s, 2H, OCH2), 6.63 (s, 1H,
CHAr), 6.89–6.92 (m, 2H, CHAr), 7.26–7.30 (m, 7H, CHAr), 10.45 (s, 1H,
906 (w), 840 (s), 807 (m), 766 (m), 732 (m), 627 (m), 578 (m) cmꢁ1
.
MS (EI, 70 eV): m/z (%)¼555 (Mþ, 22), 54 (69), 526 (12), 525 (22),
524 (62), 523 (40), 522 (89), 521 (10), 509 (11), 507 (27), 505 (19),
457 (10), 439 (16), 437 (22), 423 (10), 411 (12), 409 (17), 40 (10) 399
(31) 398 (45) 397 (100), 396 (45), 395 (30), 370 (13), 369 (15) 368
(19), 355 (12), 353 (10), 333 (10), 285 (13), 257 (14), 256 (15), 243
(17), 237 (21), 235 (32), 201 (14), 199 (12), 180 (10), 178 (10), 166
(10), 165 (30), 139 (12), 127 (10), 125 (24), 97 (14), 95 (1), 85 (12), 83
(16), 81 (13), 71 (17), 69 (20), 67 (12), 57 (31), 56 (11), 55 (29), 45
(12), 44 (57) 43 (52) 41 (29). HRMS (EI): calcd for C33H41Cl2O3
[MþH]þ: 555.2364; found: 555.2454.
OH).13CNMR(CDCl3, 62 MHz):
d¼16.3,19.3,21.1(CH3),36.2(CH), 66.3
(OCH2), 111.7, 116.7 (CHAr), 118.1 (CAr), 128.1, 128.5, 128.6, 128.7, 131.2
(CHAr), 134.1, 138.2, 143.3, 143.4 (CAr),158.7 (COH),170.0 (CO). IR (neat,
cmꢁ1): 3063 (w), 3034 (w), 2941 (w), 2880 (w), 1650 (s), 1596 (m),
1567 (m), 1482 (m), 1463 (m), 1453 (m), 1383 (m), 1343 (m), 1328 (m),
1291 (m),1222 (s),1162 (m),1069 (m),1017 (m),1005 (s), 909 (w), 866
(w), 843 (w) 817 (m), 749 (m), 733 (m), 698 (s), 644 (m), 582 (m), 546
(m) cmꢁ1. MS (EI, 70 eV): m/z (%)¼440 (Mþ, 3), 438 (3), 291 (10), 289
(11), 195 (10), 92 (13), 91 (100), 77 (10), 65 (12), 44 (12). HRMS (EI):
calcd for C24H23O3Br79 [M]þ: 438.08251; found: 438.082911, calcd for
C24H23O3Br81 [M]þ: 440.08046; found: 440.081149.
3.1.44. Methyl 3-(bis(4-methoxyphenyl)methyl)-6-hydroxy-2,4-di-
methylbenzoate (6aa). Starting with 4d (0.600 g, 1.5 mmol) and 5a
(0.429 g, 1.65 mmol), 6aa was isolated after chromatography (silica
gel, n-heptane/EtOAc)asasolid(0.194 g, 32%),mp119–120 ꢀC.1HNMR
(300 MHz, CDCl3): 1.98 (s, 3H, CH3), 2.07 (s, 3H, CH3), 3.72 (s, 3H,
OCH3), 3.81 (s, 6H, OCH3), 5.81 (s,1H, CH), 6.64 (s,1H, CHAr), 6.72–6.75
(m, 2H, CHAr), 6.90–6.93 (m, 2H, CHAr), 10.47 (s, 1H, OH). 13C NMR
3.1.48. Ethyl 6-hydroxy-3-(1-(4-methoxyphenyl)ethyl)-2,4-dimethyl-
benzoate (6ae). Starting with 4g (0.462 g, 1.5 mmol) and 5b
(0.452 g, 1.65 mmol), 6ae was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a colourless oil (0.225 g, 46%). 1H NMR
(300 MHz, CDCl3): 1.26 (d, J¼7.1 Hz, 3H, OCH2CH3), 1.53 (d, J¼7.2 Hz,
3H, CH3), 2.09 (s, 3H, CH3), 2.14 (s, 3H, CH3), 3.67 (s, 3H, OCH3), 4.28
(q, J¼7.1 Hz, 2H, OCH2CH3), 4.48 (q, J¼7.2 Hz, 1H, CH), 6.59 (s, 1H,
CHAr), 6.69–6.72 (m, 2H, CHAr), 6.92–6.95 (m, 2H, CHAr),10.44 (s,1H,
(CDCl3, 62 MHz):
d¼21.2,22.7(CH3), 49.1(CH), 52.0(OCH3), 65.2(s, 6H,
OCH3), 112.7 (CAr), 117.7, 129.9, 133.6 (CHAr), 133.6, 134.4, 140.2, 145.3,
157.7 (CAr),159.7 (COH),172.0 (CO). IR (neat, cmꢁ1): 3027 (w), 2997 (w),
2951 (w), 2834 (w), 1728 (w), 1658 (s), 1606 (m), 1568 (m), 1506 (s),
1461 (m),1438 (m),1347 (m),1286 (s),1240 (m),1172 (s),1029 (s), 949
(m), 854 (m), 802 (m), 778 (m), 700 (m), 640 (m), 573 (m) cmꢁ1. HRMS
(ESI): calcd for C25H26O5 [MþH]þ: 407.1853; found: 407.18548.
OH). 13C NMR (CDCl3, 62 MHz):
d
¼14.1, 17.5, 20.0, 22.1 (CH3), 36.8
(CH), 55.2 (OCH3), 112.9 (CAr), 113.6 (CHAr), 117.5 (CAr), 127.31 (CHAr),
135.8, 137.4, 139.2, 144.1, 157.3 (CAr), 159.3 (COH), 171.5 (CO). IR (neat,
cmꢁ1): 2975 (w), 2935 (w), 2834 (w), 1736 (w), 1655 (s), 1607 (m),
1568 (m), 1509 (s), 1462 (m), 1393 (m), 1370 (m), 1299 (m), 1242 (s),
1224 (s), 1117 (m), 1153 (m), 1074 (m), 1030 (m), 953 (w), 859 (w),
830 (m), 755 (m), 743 (m), 607 (m), 562 (m) cmꢁ1. MS (EI, 70 eV):
m/z (%)¼328 (Mþ, 40), 313 (21), 283 (16), 282 (45), 268 (18), 267
(100). HRMS (EI): calcd for C20H24O4 [M]þ: 328.16691; found:
328.167020.
3.1.45. Ethyl 3-(bis(4-methoxyphenyl)methyl)-6-hydroxy-2,4-dimethyl-
benzoate (6ab). Starting with 4d (0.600 g,1.5 mmol) and 5b (0.452 g,
1.65 mmol), 6ab was isolated after chromatography (silica gel, n-
heptane/EtOAc) as a yellowish solid (0.232 g, 37%), mp 121–122 ꢀC.
1H NMR (300 MHz, CDCl3): 1.28 (t, J¼7.1 Hz, 3H, OCH2CH3), 1.97 (s,
3H, CH3), 2.10 (s, 3H, CH3), 3.72 (s, 6H, OCH3), 4.30 (q, J¼7.1 Hz, 2H,
OCH2CH3), 5.81 (s,1H, CH), 6.64 (s,1H, CHAr), 6.72–6.75 (m, 2H, CHAr),
6.90–6.94 (m, 2H, CHAr),10.56 (s,1H, OH).13C NMR (CDCl3, 75 MHz):
3.1.49. Methyl 5-ethyl-6-hydroxy-3-(1-(4-methoxyphenyl)-ethyl)-2,4-
dimethylbenzoate (6af). Starting with 4g (0.462 g, 1.5 mmol) and 5f
(0.476 g, 1.65 mmol), 6af was isolated after chromatography (silica
gel, n-heptane/EtOAc) as a colourless oil (0.240 g, 47%). 1H NMR
(300 MHz, CDCl3): 1.03 (t, J¼7.4 Hz, 3H, CH2CH3), 1.18 (s, 3H, CH3),
1.57 (d, J¼7.2 Hz, 3H, CH3), 1.58 (s, 3H, CH3), 2.63 (q, J¼7.4 Hz, 2H,
CH2CH3), 3.71 (s, 3H, OCH3), 3.83 (s, 3H, OCH3), 4.59 (q, J¼7.2 Hz,1H,
CHAr), 6.71–6.74 (m, 2H, CHAr), 6.94–6.98 (m, 2H, CHAr), 10.54 (s, 1H,
d¼14.1, 21.1, 22.8 (CH3), 49.1 (CH), 55.2 (OCH3), 61.2 (OCH3), 61.4
(OCH2CH3), 112.9 (CAr), 113.5, 117.8, 129.9 (CHAr), 134.4, 140.2, 145.2,
157.7 (CAr), 159.7 (COH), 171.5 (CO). IR (neat, cmꢁ1): 2952 (w), 2930
(w), 2833 (w), 1726 (w),1651 (s), 1606 (m), 1581 (m), 1568 (m),1506
(s), 1461 (m), 1393 (m), 1371 (m), 1324 (m), 1298 (m), 1240 (s), 1227
(s), 1172 (s), 1142 (s), 1109 (m), 1068 (m), 1029 (s), 838 (m), 800 (m),
778 (m), 724 (m), 700 (m), 640 (m), 608 (m) cmꢁ1. HRMS (ESI): calcd
for C26H29O5 [MþH]þ: 421.19372; found: 421.18461.
OH). 13C NMR (CDCl3, 62 MHz):
d¼12.3, 16.1, 16.7, 18.8 (CH3), 28.6
(CH2), 36.1 (CH), 50.9 (OCH3), 54.2 (OCH3), 112.6,126.2 (CHAr), 134.7,
136.8, 140.9, 156.0 (CAr), 156.3 (COH), 171.6 (CO). IR (neat, cmꢁ1):
2953 (w), 2925 (w), 2871 (w), 2853 (w), 2871 (w), 2853 (w), 1736
(w), 1655 (s), 1596 (m), 1562 (m), 1509 (s), 1438 (m), 1398 (m), 1371
(m), 1303 (m), 1274 (m), 1244 (s), 1176 (s), 1106 (m), 1033 (m), 1008
(m), 951 (w), 829 (m), 807 (m), 732 (m), 636 (m), 566 (m) cmꢁ1. MS
(EI, 70 eV): m/z (%)¼342 (Mþ, 95), 327 (21), 311 (28), 310 (100), 309
(10), 296 (14), 295 (69), 284 (13), 283 (15), 282 (70), 281 (10), 269
(26), 267 (39), 253 (11), 239 (11), 238 (16), 209 (10), 155 (10), 135
(11),127 (11),119 (13),105 (10), 77 (11), 32 (12). HRMS (EI): calcd for
C21H26O4 [M]þ: 342.18256; found: 342.182444.
3.1.46. Methyl 6-hydroxy-2,4-dimethyl-3-(1-phenylethyl)benzoate
(6ac). Starting with 4e (0.417 g, 1.5 mmol) and 5a (0.429 g,
1.65 mmol), 6ac was isolated after chromatography (silica gel,
n-heptane/EtOAc) as a colourless oil (0.233 g, 55%). 1H NMR
(300 MHz, CDCl3): 1.58 (d, J¼7.0 Hz, 3H, CH3), 2.12 (s, 3H, CH3),
2.14 (s, 3H, CH3), 3.82 (s, 3H, OCH3), 4.57 (q, J¼7.4 Hz, 1H, CH), 6.63
(s, 1H, CHAr), 7.04–7.11 (m, 3H, CHAr), 10.41 (s, 1H, OH). 13C NMR
(CDCl3, 75 MHz):
d
¼17.2, 20.1, 22.1 (CH3), 37.6 (CH), 51.9 (OCH3),
112.7 (CAr), 117.6, 125.4, 126.3, 128.2 (CHAr), 135.9, 139.2, 144.5,
145.4 (CAr), 159.4 (COH), 172.0 (CO). IR (neat, cmꢁ1): 3083 (w), 3024
(w), 2953 (w), 2876 (w), 1729 (w), 1659 (s), 1600 (m), 1570 (m),
1494 (m), 1460 (m), 1439 (m), 1348 (m), 1327 (m), 1266 (m), 1227
(s), 1195 (m), 1154 (m), 1072 (m), 1020 (m), 950 (w), 859 (w), 804
(m), 723 (m), 698 (m), 647 (m), 565 (w) cmꢁ1. MS (EI, 70 eV): m/z
(%)¼284 (Mþ, 54), 253 (26), 252 (95), 238 (19), 237 (100), 166 (11),
Acknowledgements
We are grateful for Mr. Obaid-Ur-Rahman Abid for his help.
Financial support from the State of Pakistan (HEC scholarship for

1652
R.A. Khera et al. / Tetrahedron 66 (2010) 1643–1652
Singh, S.; Sharma, S. K.; Gupta, S.; Malhotra, S.; Tyagi, O. D.; Vardhan, A.; Pati, H.
N. Indian J. Chem., Sect. B 1996, 35, 220.
R.A. and I.U.) and from the DAAD (scholarships for R.A. K. and I.U.) is
gratefully acknowledged.
4. (a) Jovel, I.; Mertins, K.; Kischel, J.; Zapf, A.; Beller, M. Angew. Chem. 2005,117, 3981;
Angew. Chem., Int. Ed. 2005, 44, 3913; (b) Mertins, K.; Jovel, I.; Kischel, J.; Zapf, A.;
Beller, M. Angew. Chem. 2005, 117, 242; Angew. Chem., Int. Ed. 2005, 44, 238.
5. (a) Christoffers, J. J. Chem. Soc., Perkin Trans. 11997, 3141; (b) Christoffers, J. Eur. J.
Org. Chem. 1998, 7, 1259; (c) Christoffers, J.; Oertling, H. Tetrahedron 2000, 56,
1339.
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12. CCDC-756115, 756,116, and 756,117 contain all crystallographic details of this
publication and is available free of charge at www.ccdc.cam.ac.uk/conts/re-
trieving.html or can be ordered from the following address: Cambridge Crys-
tallographic Data Centre, 12 Union Road, GB-Cambridge CB21EZ; Fax: þ44 1223
336 033; or deposit@ccdc.cam.ac.uk.