S. R. Waldvogel et al.
FULL PAPER
1
), 125.2 (C-3), 128.5 (C-6), 130.0 (C-5), 132.0 (C-4), 149.2 (C-2)
Conclusions
+
·
ppm. MS (EI, 70 eV): m/z (%) = 242 (100) [M] , 227 (29), 209 (11),
By simple anodic oxidation employing basic media 2,4- 199 (18), 173 (5), 115 (3), 91 (5), 77 (3) ppm. C H O (242.13):
1
6
18
2
dimethylphenol gives a facile access to novel pentacyclic calcd. C 79.31, H 7.49; found C 79.21, H 7.35.
structures. Besides a major pentacyclic scaffold 4 three
minor pentacyclic components were isolated and fully char-
acterized. Since the novel structure 4 is easily prepared and nol, ref. m.p. 137 °C). IR (KBr): ν = 2966, 2986, 1679, 1475, 1369,
obtained diastereomerically pure, it might serve as ad- 1210, 990, 868 cm . H NMR (400 MHz, CDCl ): δ = 1.51 (s, 3
(
3
4aRS,9bRS)-4a,9b-Dihydro-2,6,8,9b-tetramethyl-4H-dibenzofuran-
-one (3): 1.94 g, 8 mmol, 32%. Colourless solid, m.p. 138 °C (etha-
[8]
˜
–
1 1
3
3 3 3
dressable scaffold for further chemical modifications. The H, 9b-CH ), 1.71 (s, 3 H, 2-CH ), 2.14 (s, 3 H, 8-CH ), 2.28 (s, 3
2
3
A
3
H, 6-CH ), 2.77 (dd, J = 17.6, J = 3.9 Hz, 1 H, 4-H ), 3.06 (dd,
construction of the pentacyclic architecture most likely in-
volves Pummerer’s ketone 3 as a synthetic intermediate.
Based on the proposed mechanism the direct synthesis of
mixed pentacyclic aggregates of different phenols will be
reported in due course.
2
3
B
3
3
J = 17.6, J = 3.9 Hz, 1 H, 4-H ), 4.61 (dd, J = 3.9, J = 3.9 Hz,
H, 4a-H), 6.21 (s, 1 H, 1-H), 6.80 (s, 1 H, 7-H), 6.82 (s, 1 H, 9-
H) ppm. C NMR (100 MHz, CDCl
CH ), 20.5 (9b-CH ), 21.7 (8-CH ), 37.8 (C-4), 45.2 (C-9b), 86.6
C-4a), 120.0 (C-9a), 120.1 (C-6), 130.6 (C-9), 130.8 (C-7), 131.9
C-8), 132.3 (C-2), 145.4 (C-1), 155.3 (C-5a), 195.0 (C-3) ppm. MS
1
1
3
3 3
): δ = 14.7 (6-CH ), 15.7 (2-
3
3
3
(
(
(
+
·
EI, 70 eV): m/z (%) = 242 (100) [M] , 227 (96), 199 (49) ppm.
Experimental Section
16 18 2
C H O (242.13): calcd. C 79.31, H 7.49; found C 79.15, H 7.52.
General Remarks: All reagents were used in analytical grades. Sol-
vents were desiccated if necessary by standard methods. Column
chromatography was performed on silica gel (particle size 63–
(1SR,3aSR,8aRS)-3a,8a-dihydro-2,3a,5,7,5Ј,7Ј-hexamethylspiro-
[cyclopenta[b]benzo[d]furan-1,3Ј(3ЈH)-benzofuran]-2Ј-one (4): 1.07 g,
3 mmol, 18%. Colourless solid, m.p. 133 °C (methanol). IR (KBr):
–
1
2
00 μm, Merck, Darmstadt, Germany) using mixtures of cyclohex-
ane with ethyl acetate as eluents. TLC was done on silica gel 60
254 on glass (Merck, Darmstadt, Germany). Melting points were
ν˜ = 2972, 2921, 1794, 1628, 1481, 1227, 1191, 1120, 1087, 858 cm .
1
H NMR (600 MHz, CDCl
H, 3a-CH ), 2.03 (s, 3 H, 7-CH
H, 7Ј-CH ), 2.30 (s, 3 H, 5-CH
3-H), 6.37 (s, 1 H, 4Ј-H), 6.79 (s, 1 H, 6Ј-H), 6.83 (s, 1 H, 4-H),
3
): δ = 1.36 (s, 3 H, 2-CH
), 2.19 (s, 3 H, 5Ј-CH
), 5.02 (s, 1 H, 8a-H), 5.80 (s, 1 H,
3
), 1.67 (s, 3
F
3
3
3
), 2.29 (s, 3
determined on a Melting Point Apparatus SMP3 (Stuart Scientific,
Watford Herts, UK) and were uncorrected. IR spectra were re-
corded on a Perkin–Elmer FT-IR Spectrometer Paragon 500. Mi-
croanalysis was performed using a Vario EL III (Elementar-Ana-
lysensysteme, Hanau, Germany). NMR spectra were recorded on
a Bruker ARX 300, AMX 300, or AMX 400 (Analytische Mes-
stechnik, Karlsruhe, Germany) or on a Varian Unity plus 600 MHz
3
3
1
3
6.93 (s, 1 H, 6-H) ppm. C NMR (150 MHz, CDCl
CH ), 14.9 (7-CH ), 15.0 (7Ј-CH ), 20.8 (5-CH ), 20.9 (5Ј-CH
24.6 (3a-CH ), 60.2 (C-3a), 68.3 (C-1), 95.5 (C-8a), 119.6 (C-7),
3
): δ = 13.3 (2-
3
3
3
3
3
),
3
120.1 (C-7Ј), 120.5 (C-4), 124.8 (C-4Ј), 130.2 (C-6), 130.6 (C-5),
131.3 (C-6Ј), 132.7 (C-3b), 133.1 (C-5Ј), 136.7 (C-3), 136.8 (C-2),
(
Varian Associated, Palo Alto, CA, USA) using TMS as internal
standard or CDCl
with δ = 7.26 ppm for 1H NMR, and δ =
7.0 ppm for 13C NMR spectroscopy. The NMR spectroscopic
data are given in ppm. Mass spectra were obtained on a MAT8200
Finnigan, Bremen, Germany) employing EI, or on a MS50
Kratos, Manchester, England) or MAT95XL (Finnigan, Bremen,
150.2 (C-7aЈ), 154.7 (C-7a), 178.2 (C-2Ј) ppm. MS (EI, 70 eV): m/
+·
z (%) = 360 (100) [M] , 345 (54), 317 (69) ppm. C24
H
24
O
3
(360.17):
3
7
calcd. C 79.97, H 6.71; found C 79.78, H 6.71.
(
6RS,6aSR,11bSR)-6a,11b-Dihydro-1,3,6,8,10,11b-hexamethyl-6H-
(
(
benzofuro[2,3-c]dibenzofuran-5-one (5): 290 mg, 0.8 mmol, 5 %.
Colourless solid, m.p. 226 °C (dichloromethane). IR (KBr): ν˜ =
Germany) employing EI and HRMS.
–1 1
2
923, 1687, 1481, 1214, 1120, 939, 852 cm . H NMR (400 MHz,
3
Anodic Oxidation of 2,4-Dimethylphenol: 2,4-Dimethylphenol
(
drate in methanol (25 mL) and transferred into a non-divided stan-
CDCl
CH
CH
3
): δ = 1.59 (d, J = 7.0 Hz, 3 H, 6-CH
), 2.09 (s, 3 H, 8-CH ), 2.31 (s, 3 H, 10-CH
), 2.43 (s, 3 H, 1-CH
3
), 1.88 (s, 3 H, 11b-
6.1 g, 50 mmol) was dissolved in 0.1 m barium hydroxide octahy-
3
3
3
3
), 2.38 (s, 3 H, 3-
3
3
3
), 3.03 (qd, J = 7.0, J = 3.2 Hz, 1 H,
[
12]
3
dard electrolysis cell equipped with two platinum sheets as anode
and cathode, respectively. At 20 °C a galvanostatic electrolysis with
a current density of 12.5 mA/cm² was performed. During the elec-
trolysis vigorous stirring is necessary and the formation of a light
brown precipitate can be observed. After ca. 8300 C (1.7 F/mol)
were applied the mixture was filtered and the precipitate was
washed with methanol (10 mL), dried in vacuo and purified by
sublimation (105 °C, 4.3×10–3 mbar) yielding analytically pure 4.
The filtrate was diluted with water (100 mL) and extracted with
tert-butyl methyl ether (TBME, 3×30 mL). The combined organic
6-H), 4.76 (d, J = 3.2 Hz, 1 H, 6a-H), 6.78 (s, 1 H, 9-H), 6.88 (s,
1
3
1 H, 2-H), 7.15 (s, 1 H, 11-H), 7.66 (s, 1 H, 4-H) ppm. C NMR
(100 MHz, CDCl ): δ = 10.9 (6-CH ), 14.7 (8-CH ), 14.8 (1-CH ),
20.6 (11b-CH ), 20.9 (10-CH ), 21.2 (3-CH ), 42.0 (C-6), 46.3 (C-
3
3
3
3
3
3
3
11b), 92.4 (C-6a), 114.0 (C-4b), 119.1 (C-4), 120.2 (C-8), 120.8 (C-
1), 121.7 (C-11), 123.1 (C-4a), 127.3 (C-2), 130.0 (C-11a), 130.7 (C-
10), 131.2 (C-9), 134.1 (C-3), 152.8 (C-12a), 154.8 (C-7a), 167.3 (C-
+·
11c), 193.1 (CO) ppm. MS (EI, 70 eV): m/z (%) = 360 (26) [M] ,
345 (21), 302 (22), 256 (100), 241 (56), 213 (29). HRMS: calcd.
360.1725; found 360.1723.
4
layers were washed with brine (50 mL), dried (MgSO ), and con-
centrated in vacuo. Purification by column chromatography (cyclo-
hexane/ethyl acetate, 98:2) yielded 2, 3, 5 and the mixture of 6 and
(
4ЈRS,4aЈRS,9bЈSR)-4aЈ,9bЈ-Dihydro-4,6-dimethylspiro[benzo[1,3]-
dioxol-2,4Ј-dibenzofuran]-3Ј-one (6): 112 mg, 0.3 mmol, 2 %.
Colourless solid, m.p. 201 °C (dichloromethane). IR (KBr): ν˜ =
2
CDCl
CH
CH
7, which was separated by crystallization (dichloromethane/hep-
–
1 1
924, 1701, 1496, 1281, 1193, 1027, 978 cm . H NMR (400 MHz,
tane).
3
3
): δ = 1.71 (s, 3 H, 9bЈ-CH
), 2.17 (s, 3 H, 4-CH ), 2.23 (s, 3 H, 6Ј-CH
), 2.30 (s, 3 H, 8Ј-CH
3
), 1.81 (d, J = 1.3 Hz, 3 H, 2Ј-
), 2.29 (s, 3 H, 6-
3
), 4.68 (d, J = 1.8 Hz, 1 H, 4aЈ-H),
3
,3Ј,5,5Ј-Tetramethyl-2,2Ј-biphenol (2): 195 mg, 0.8 mmol, 3%.
3
3
3
[15]
3
Colourless solid, m.p. 135 °C (cyclohexane, ref.
m.p. 134–
3
1
7
5
35 °C). IR (KBr): ν˜ = 3518, 2918, 1466, 1212, 1185, 1113, 859,
6.34–6.35 (m, 1 H, 1Ј-H), 6.48 (s, 1 H, 5-H), 6.51 (s, 1 H, 7-H),
–1
1
13
84 cm . H NMR (300 MHz, CDCl
.04 (s, 2 H, OH), 6.85 (s, 2 H, 4-H), 6.98 (s, 2 H, 6-H) ppm. 13C
): δ = 16.1 (3-CH ), 20.4 (5-CH ), 122.2 (C- CH
3
): δ = 2.27 (s, 12 H, CH
3
), 6.82 (s, 1 H, 9Ј-H), 6.84 (s, 1 H, 7Ј-H) ppm. C NMR (100 MHz,
CDCl
3
): δ = 14.8 (4-CH
3 3 3
), 14.9 (6Ј-CH ), 16.1 (2Ј-CH ), 20.8 (8Ј-
NMR (75 MHz, CDCl
3
3
3
3
), 21.1 (6-CH
3
), 23.2 (9bЈ-CH
3
), 48.1 (C-9bЈ), 87.6 (C-4aЈ),
244
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Eur. J. Org. Chem. 2006, 241–245