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Organic & Biomolecular Chemistry
Page 10 of 15
DOI: 10.1039/C8OB00409A
ARTICLE
isolated but could only be identified as a complex 7.2 Hz), 4.32 (1 H, dd,
Journal Name
J
= 11.1 Hz, 5.3 Hz), 4.25 (1 H,
mixture of products.
dd, J = 11.2 Hz, 6.2 Hz), 4.08 (1 H, dd, J 11.2 Hz, 6.9
Hz), 3.84 (3 H, s), 3.80 (3 H, s), 3.79 (2 H, s), 3.77 (3 H,
s), 3.72 (2 H, s), 3.69 (2 H, s), 3.41 – 3.35 (1 H, m), 3.32
General Procedure for the Co(III) Catalyzed
Oxidation of 1-4:
(1 H, q,
J = 6.9 Hz), 2.06 (2 H, s), 1.99 (2 H, s), 1.93 (3
H, s), 1.90 (3 H, s). 13CNMR (100 MHz, CDCl3, mixture
of diastereomers): 170.9, 170.7, 169.9, 169.7, 148.5,
148.4, 148.1, 148.0, 146.2, 145.9, 145.6, 145.2, 130.2,
130.2, 130.1, 130.1, 121.1, 121.0, 120.2, 120.1, 114.2,
114.0, 112.1, 112.0, 110.8, 110.8, 110.1, 109.7, 76.3,
75.5, 64.6, 55.8, 55.8, 55.8, 55.8, 55.8, 55.7, 49.8, 49.5,
A mixture of lignin model (1 eq.), Co(OAc)2·4H2O (2
eq.) and AcOH (2 mL/mmol) were stirred under an O2
atmosphere (balloon) at 120 C for 19h. The mixture was
extracted with DCM and the organic layer was washed
with chilled water. The combined organic layers were
dried over Na2SO4 and concentrated under vacuum. The
crude products were purified by column chromatography
on silica gel.
o
21.2, 21.0, 20.9, 20.8. HRMS (ESI, NH4Cl buffer)
m/z
[M + NH4]+ calcd for C22H30NO8 436.1971, found
436.1965.
Co(III) oxidation of 1. Products afforded from a mixture
Ester 22 (mixture of diastereomers): 1HNMR (400 MHz,
CDCl3,): 7.08 ꢀ 7.02 (2 H, m), 6.99 (1 H, s), 6.93 (1 H, d,
of
1 (90 mg, 0.26 mmol) and Co(OAc)2·4H2O (129 mg,
0.52 mmol) were purified by column chromatography on
silica gel (hexane/ethyl acetate = 1:1) to give aldehyde 13
(35 mg, 0.21 mmol, 81.5%).
J
= 8.1 Hz), 6.91 ꢀ 6.88 (2 H, m), 6.88 ꢀ 6.84 (2 H, m),
6.82 (1 H, dd, = 8.2 Hz, 1.8 Hz), 6.77 (1 H, d, = 1.8
Hz), 6.72 (1 H, d, = 8.2 Hz), 6.64 (1 H, dd, = 8.2 Hz,
2.0 Hz), 6.58 (1 H, s), 6.49 (1 H, d, = 1.9 Hz), 5.66 (1
H, s), 5.53 ꢀ 5.51 (1 H, m), 5.15 (2 H, s), 4.87 (2 H, d,
J
J
J
J
J
Co(III) oxidation of 2. Products afforded from a
J
=
mixture of
2 (90 mg, 0.27 mmol) and Co(OAc)2·4H2O
1.2 Hz), 3.93 (3 H, s), 3.91 (3 H, s), 3.90 (3 H, s), 3.89 (3
H, s), 3.76 (3 H, s), 3.54 (3 H, s), 2.06 (3 H, s), 2.06 (2 H,
s). 13CNMR (100 MHz, CDCl3, mixture of
diastereomers): 171.0, 170.7, 149.1, 148.8, 148.8, 148.4,
146.3, 145.7, 145.3, 144.9, 134.2, 133.9, 133.2, 132.4,
131.0, 129.4, 129.0, 128.4, 123.3, 122.4, 121.1, 118.7,
114.4, 113.9, 112.2, 111.4, 111.3, 111.2, 111.1, 109.6,
69.6, 62.2, 55.9, 55.9, 55.9, 55.9, 55.8, 55.4, 29.7, 21.0.
(134 mg, 0.54 mmol) were purified column
chromatography on silica gel (hexane/ethyl acetate = 1:1)
(hexane/ethyl acetate = 3:1) to give a yellow solid
stilbene (19) (7 mg, 0.024 mmol, 9.1%), a yellow oil
diester (20) (1.8 mg, 0.006 mmol, 2.4%), a yellow oil
isomeric diester (21) (31.5 mg, 0.075 mmol, 27.9%) and
a yellow oil isomeric ester (22) (8.5 mg, 0.02 mmol,
7.5%).
HRMS (ESI)
m/z
[MꢀCH3COO]+ calcd for C18H19O4
299.1283, found 299.1279.
19
1HNMR (400 MHz, CDCl3): 7.04 (1 H, d,
7.02 (2 H, dd, = 4.9 Hz, 3.1 Hz), 7.00 ꢀ 6.98 (1 H, m),
6.91 ꢀ 6.87 (3 H, m), 6.84 (1 H, d, = 8.2 Hz), 5.62 (1 H,
:
(E)-4-(3,4-dimethoxystyryl)-2-methoxyphenol
J
= 1.9 Hz),
Co(III) oxidation of 3. Products afforded from a mixture
J
of
0.57 mmol) were purified by column chromatography on
silica gel (hexane/ethyl acetate = 1:1), gave the ꢀacetate
from as a brown oil (90 mg, 0.25 mmol, 88%).
3 (90 mg, 0.28 mmol) and Co(OAc)2·4H2O (142 mg,
J
s), 3.94 (3 H, s), 3.93 (3 H, s), 3.89 (3 H, s). 13CNMR
(100 MHz, CDCl3): 149.1, 148.6, 146.7, 145.3, 130.7,
130.2, 126.8, 126.3, 120.1, 119.5, 114.5, 111.3, 108.6,
108.0, 55.9, 55.9, 55.8.
γ
3
23:((2-(3,4-dimethoxyphenyl)-7-methoxy-2,3-dihydro-
benzofuran-3-yl)methyl acetate): HNMR (400 MHz,
1
Diester 20
2-diacetate). 1HNMR (400 MHz, CDCl3): 6.94 (1 H,
ddd, = 8.2 Hz, 2.0 Hz, 0.4 Hz), 6.90 (1 H, d, = 2.0
Hz), 6.85 (1 H, d, = 8.3 Hz), 5.97 (1 H, dd, = 6.7 Hz,
: (1-(3,4-dimethoxyphenyl)-1,2-ethanediol-1,
CDCl3): 6.95 ꢀ 6.79 (6 H, m), 5.45 (1 H, d,
4.42 (1 H, dd, = 11.2 Hz, 5.6 Hz), 4.30 (1 H, dd,
= 4.7 Hz),
J = 7.5 Hz),
J
J =
J
J
11.1 Hz, 7.4 Hz), 3.87 (3 H, s), 3.84 (6 H, d,
J
J
J
3.82 ꢀ 3.76 (1 H, m), 2.00 (3 H, s). 13CNMR (100 MHz,
CDCl3): 170.8, 149.1, 149.1, 148.0, 144.5, 133.0, 127.4,
121.5, 118.8, 116.6, 112.1, 110.9, 109.2, 88.2, 65.5, 56.0,
55.9, 55.9, 50.4, 20.8.
5.4 Hz), 4.31 (1 H, s), 4.30 (1 H, s), 3.89 (3 H, s), 3.85 (3
H, s), 2.10 (3 H, s), 2.05 (3 H, s). 13CNMR (100 MHz,
CDCl3): 170.4, 169.8, 149.2, 149.0, 128.9, 119.2, 111.1,
110.0, 73.0, 65.9, 55.8, 55.7, 20.9, 20.6.
Co(III) oxidation of 4. Products afforded from a
mixture of 4 (63 mg, 0.21 mmol) and Co(OAc)2·4H2O
(0.41 mg, 0.41 mmol) were purified by column
chromatography on silica gel (hexane/ethyl acetate = 1:1)
to give a phenyl acetate from 4 as a brown oil (49 mg,
0.13 mmol, 70%). Chromatography immobile products
were also observed.
Diester
diastereomers ): 6.83 – 6.77 (1 H, m), 6.77 ꢀ 6.73 (2 H,
m), 6.72 (1 H, d, = 2.5 Hz), 6.70 ꢀ 6.67 (1 H, m), 6.65
(2 H, dd, = 7.8 Hz, 1.9 Hz), 6.61 (1 H, d, = 1.9 Hz),
6.55 (1 H, dd, = 8.2 Hz, 2.0 Hz), 6.45 (1 H, d, = 2.0
Hz), 6.00 (1 H, d,
(
21): 1HNMR (400 MHz, CDCl3, mixture of
J
J
J
J
J
J
= 7.6 Hz), 5.90 (1 H, d,
J
= 8.7 Hz),
5.61 (1 H, s), 5.53 (1 H, s), 4.47 (1 H, dd,
J = 11.1 Hz,
10 | J. Name., 2012, 00, 1-3
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