Table 1 The reaction of methyl coumalate with alkenes
Entry Substrate Yield (%) R group
29.7, 29.6, 29.5, 23.5, 14.4; HRMS (FAB) m/z exact mass calc.
for C17H26O2 (MH+) 263.2006, found 263.2005.
Product
Methyl 4-benzylbenzoate (4d). Spectral data matches that in
1
2
3
4
5
6
1-Nonene
1-Decene
1-Undecene
Allyl benzene
Allyl phenyl ether 61
Allyl heptyl ether 51
52
70
63
83
–(CH2)6CH3
4a
4b
4c
4d
4e
the literature.8
–(CH2)7CH3
–(CH2)8CH3
–CH2Ph
–CH2OPh
–CH2O(CH2)6CH3 4f
Mehyl
(300 MHz, CDCl3): d 8.05 (d, J = 7 Hz, 2H), 7.51 (d,
J = 7 Hz, 2H), 7.31–6.91 (m, 5H), 5.13 (s, 2H), 3.92 (s, 3H); 13
4-(phenoxymethyl)benzoate
(4e). 1H
NMR
C
NMR (400 MHz, CDCl3): d 167.1, 158.6, 142.5, 129.1, 128.9,
127.2, 121.4, 115.0, 69.5, 52.4; HRMS (FAB) m/z exact mass
calc. for C15H14O3 243.1016 (MH+), found 243.1009.
Table 2 The reaction of coumalic acid with alkenes
Entry Substrate Yield (%) R group
Product
Methyl 4-(heptyloxymethyl)benzoate (4f). 1H NMR
(300 MHz, CDCl3): d 8.03 (d, J = 7 Hz, 2H), 7.39 (d, J = 7 Hz,
2H), 4.55 (s, 2H), 3.75 (m, 2H), 1.53–1.28 (m), 0.88; 13C NMR
(400 MHz, CDCl3): d 167.2, 144.3, 130.3, 128.9, 127.8, 72.0,
70.7, 52.3, 32.1, 29.9, 29.4, 26.4, 22.9, 14.3; HRMS (FAB) m/z
exact mass calc. for C16H24O3 265.1798 (MH+), found 265.1804.
1
2
3
4
5
6
1-Heptene
1-Decene
1-Undecene
Allyl benzene
Allyl phenyl ether 65
Allyl heptyl ether 66
85
72
69
79
–(CH2)6CH3
8a
8b
8c
8d
8e
–(CH2)7CH3
–(CH2)8CH3
–CH2Ph
–CH2OPh
–CH2O(CH2)6CH3 8f
4-Pentylbenzoic acid (8a). 1H NMR (400 MHz, CDCl3): d
12.06–11.6 (br, 1 H), 8.05 (d, J = 7 Hz, 2H), 7.29 (d, J = 7 Hz, 2H)
2.70 (t, J = 7 Hz, 2H), 1.73–1.53 (m, 2H) 1.53–1.22 (m, 4H), 0.93
(t, J = 7 Hz, 3H); 13C NMR (100 MHz, CDCl3): d 172.8, 149.8,
130.5, 128.8, 127.1, 36.3, 31.7, 31.1, 22.8, 14.3; HRMS (QTOF)
m/z exact mass calc. for C12H16O2 192.115, found 191.1078 (M–
H)-.
ambient temperature, the reaction became homogeneous at
around 140 ◦C. The results are shown in Table 2.
The rationale for the remarkable regioselectivity is unclear.
The result may simply be due to non-bonded steric interactions
favoring the formation of adduct 6. However, we cannot rule out
the production of both 6 and 7 in equilibrium with the starting
materials, followed by the selective oxidation by Pd/C of 6.
4-Octylbenzoic acid (8b). 1H NMR (300 MHz, CDCl3): d
12.54–12.12 (br, 1 H), 8.02 (d, J = 7 Hz, 2H), 7.27 (d, J = 7 Hz,
2H), 2.67 (t, J = 7 Hz, 2H), 1.70–1.51 (m, 2H), 1.37–1.17 (m,
10H), 0.88 (t, J = 7 Hz); 13C NMR (100 MHz, CDCl3): d 178.7,
149.8, 130.5, 128.8, 115.6, 36.4, 32.1, 31.4, 29.9, 29.7, 29.5, 22.9,
14.4; HRMS (QTOF) m/z exact mass calc. for C15H22O2 234.162,
found 233.1547 (M–H)-.
3. Experimental
All starting materials were commercially available unless other-
wise noted. Methyl coumalate was prepared via the methylation
of coumalic acid.9 Allyl heptyl ether was prepared from 1-
heptanol and allyl bromide.10
4-Nonylbenzoic acid (8c). 1H NMR (300 MHz, CDCl3): d
12.42–11.99 (br, 1 H), 8.03 (d, J = 7 Hz, 2H), 7.27 (d, J = 7 Hz,
2H), 2.67 (t, J = 7 Hz, 2H), 1.70–1.55 (m, 2H), 1.40–1.20 (m,
12H), 0.89 (t, J = 7 Hz, 3H); 13C NMR (100 MHz, CDCl3):
d 172.8, 149.8, 130.5, 128.8, 127.1, 36.4, 32.2, 31.4, 29.9, 29.7,
29.6, 29.5, 22.9, 14.4; HRMS (QTOF) m/z exact mass calc. for
C16H24O2 248.1776, found 247.1704 (M–H)-.
Typical reaction procedure: Methyl coumalate (200 mg),
olefin (5 equiv.) and 50 mg 10% Pd/C were dissolved in 7 mL
mesitylene. The reaction was heated in a sealable tube in an oil
bath at 200 ◦C for 12–16 h. The reaction vessel was then cooled
R
to rt, the catalyst removed by filtering through a pad of Celiteꢀ
and washed with ether. The filtrate was then concentrated
and purified by silica gel chromatography (10 : 1 hexanes/ethyl
acetate).
4-Benzylbenzoic acid (8d). 1H NMR (300 MHz, CDCl3): d
12.3–11.2 (br, 1H), 8.05 (d, J = 7 Hz, 2H), 7.40–7.21 (m, 7H),
4.06 (s, 2H); 13C NMR (100 MHz, CDCl3): d 172.5, 147.8, 140.2,
129.2, 129.1, 128.8, 128.3, 127.5, 126.7, 42.3; HRMS (QTOF)
m/z exact mass calc. for C14H12O2 212.0837, found 211.0765
(M–H)-.
Methyl 4-heptylbenzoate (4a). 1H NMR (300 MHz, CDCl3):
d 7.95 (d, J = 7 Hz, 2H), 7.23 (d, J = 7 Hz, 2H), 3.90 (s, 3H), 2.65
(m, 2H), 1.59–1.26 (m), 0.88; 13C NMR (400 MHz, CDCl3): d
167.4, 144.3, 129.9, 128.9, 127.3, 52.3, 32.1, 30.0, 29.2, 26.4, 22.9,
14.3; HRMS (FAB) m/z exact mass calc. for C15H22O2 235.1693
(MH+), found 235.1699.
4-(Phenoxymethyl)benzoic acid (8e). 1H NMR (300 MHz,
CDCl3): d 9.94 (br, 1H), 7.36–7.25 (m, 6H), 7.12–6.80 (m, 6H),
5.16 (s, 2H); 13C NMR (100 MHz, CDCl3): d 172.0, 152.6, 141.0,
130.5, 130.0, 129.7, 127.6, 121.1, 115.6, 69.3; HRMS (QTOF)
m/z exact mass calc. for C14H12O3 228.0789, found 227.0714
(M–H)-.
Methyl 4-octylbenzoate (4b). 1H NMR (300 MHz, CDCl3):
d 7.94 (d, J = 7 Hz, 2H), 7.24 (d, J = 7 Hz, 2H), 3.90 (s, 3H),
2.63 (m, 2H), 1.59–1.26 (m), 0.88; 13C NMR (400 MHz, CDCl3):
d; 167.4, 148.7, 129.8, 128.6, 127.4, 52.1, 36.2, 32.1, 31.4, 29.8,
29.7, 29.5, 22.9, 14.3; HRMS (FAB) m/z exact mass calc. for
C16H24O2 249.1849 (MH+), found 249.1815.
4-(Heptyloxy)methyl)benzoic acid (8f). 1H NMR (300 MHz,
CDCl3): d 9.93 (br, 1H), 8.05 (d, J = 7 Hz, 2H), 7.43 (d, J = 7 Hz,
2H), 4.56 (s, 2H), 3.63 (d, J = 7 Hz, 2H), 1,64–1.15 (m, 10 H), 0.87
(t, J = 7 Hz, 3H); 13C NMR (100 MHz, CDCl3): d 171.9, 145.1,
128.8, 128.0, 127.5, 71.5, 71.1, 32.1, 29.9, 29.4, 26.5, 22.9, 14.3;
Methyl 4-nonylbenzoate (4c). 1H NMR (300 MHz, CDCl3):
d 7.96 (d, J = 7 Hz, 2H), 7.24 (d, J = 7 Hz, 2H), 3.90 (s, 3H),
2.64 (m, 2H), 1.59–1.26 (m), 0.88; 13C NMR (400 MHz, CDCl3):
d 167.5, 148.7, 129.8, 128.6, 127.4, 52.1, 36.3, 32.1, 31.4, 29.8,
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The Royal Society of Chemistry 2011
Green Chem., 2011, 13, 2734–2736 | 2735
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