E. Masson, M. Schlosser
FULL PAPER
= 0.00 ppm) and coupling constants J are given in Hz. Coupling
solution of sec-butyllithium (50 mmol) in cyclohexane (40 mL) and
patterns are abbreviated as s (singlet), d (doublet), t (triplet), q tetrahydrofuran (40 mL) cooled in a dry ice/toluene bath for
(quadruplet), m (multiplet), symm. m (symmetrical multiplet), dd
(doublet of doublets), dt (doublet of triplets), etc. Elementary
analyses were performed by the laboratory of I. Beetz (96301 Kron-
ach, Germany). The expected percentages were calculated with the
atomic weight numbers listed in the 1993 IUPAC recommenda-
tions.
45 min. At –75 °C, the yellow suspension was transferred through
Teflon tubing into furan (73 mL, 68 g, 1.0 mol) whilst stirring. The
mixture was diluted with hexanes (0.25 L) and filtered through a
pad of alumina. After evaporation of the solvents, the residue was
distilled to give a viscous yellow oil. Yield: 4.50 g (42%). B.p. 83–
86 °C/1 Torr. 1H NMR: δ = 7.25 (symm. m, 1 H), 7.09 (dd, J =
7.7, 1.0 Hz, 1 H), 7.03 (dd, J = 5.5, 1.8 Hz, 1 H), 7.01 (dd, J = 5.5,
1.8 Hz, 1 H), 6.95 (t, J = 7.3 Hz, 1 H), 5.84 (symm. m, 1 H), 5.70
(symm. m, 1 H), 0.33 (s, 9 H) ppm. 13C NMR: δ = 155.0, 147.5,
143.2, 142.8, 132.0, 129.6, 124.0, 120.9, 82.6, 82.0, –0.4 (3 C) ppm.
C13H16OSi (216.35): calcd. C 72.17, H 7.45; found C 72.23, H 7.40.
Starting Materials
(2-Fluorophenyl)trimethylsilane: sec-Butyllithium (0.25 mol) in cy-
clohexane (0.20 L) was added to a solution of fluorobenzene
(24 mL, 24 g, 0.25 mol) in tetrahydrofuran (0.25 L) at –75 °C in the
course of 15 min. After 15 min, the white suspension was treated
with chlorotrimethylsilane (32 mL, 27 g, 0.25 mol) and, when the
temperature had reached +25 °C, the mixture was poured into
water (20 mL). After evaporation of the solvents from the filtered
solution, distillation afforded a colorless oil. Yield: 35.3 g (84%).
B.p. 60–62 °C/20 Torr (ref.[28]: b.p. 60 °C/15 Torr). n2D0 = 1.4760
1,4-Epoxy-1,4-dihydro-5-fluoro-8-(trimethylsilyl)naphthalene (3): A
solution of (2-chloro-4-fluorophenyl)trimethylsilane (2.0 g,
10 mmol) in tetrahydrofuran (10 mL) was treated with a solution
of butyllithium (10 mmol) in tetrahydrofuran (10 mL) at –75 °C.
After 2 h, the solution was transferred through Teflon tubing into
furan (15 mL, 14 g, 0.20 mol). The reaction mixture was diluted
with hexanes (50 mL) and filtered through a pad of alumina.
Chromatography using alumina as the support (50 mL) and hex-
anes as the eluent afforded a yellow oil. Yield: 0.87 g (73%). 1H
NMR: δ = 7.1 (m, 3 H), 6.67 (t, J = 8.4 Hz, 1 H), 5.97 (symm. m,
1 H), 5.84 (symm. m, 1 H), 0.31 (s, 9 H) ppm. 13C NMR: δ = 158.9
(d, J = 4 Hz), 158.1 (s), 155.6 (s), 142.8 (d, J = 8 Hz), 132.5 (d, J
= 5 Hz), 132.3 (s), 128.6 (d, J = 4 Hz), 112.9 (d, J = 21 Hz), 82.2
(d, J = 2 Hz), 79.0 (s), –0.3 (s, 3 C) ppm. C13H15FOSi (234.34):
calcd. C 66.63, H 6.45; found C 66.40, H 6.54.
(ref.[28]: n2D0 = 1.4780). H NMR: δ = 7.4 (m, 1 H), 7.3 (m, 1 H),
1
7.12 (tt, J = 7.3, 1.0 Hz, 1 H), 6.98 (td, J = 8.5, 1.0 Hz, 1 H), 0.31
(d, J = 1.0 Hz, 9 H) ppm.
(2-Chloro-4-fluorophenyl)trimethylsilane: A solution of 1-bromo-2-
chloro-4-fluorobenzene (5.2 g, 25 mmol) in tetrahydrofuran
(50 mL) was added dropwise in the course of 45 min to a solution
of butyllithium (25 mmol) in hexanes (50 mL) at –100 °C. The mix-
ture was treated with chlorotrimethylsilane (3.2 mL, 2.7 g,
25 mmol), allowed to reach +25 °C, and washed with water
(50 mL). Upon distillation a colorless oil was collected. Yield:
3.90 g (77%). B.p. 35–36 °C/1 Torr. n2D0 = 1.4931. 1H NMR: δ =
7.42 (dd, J = 8.2, 6.8 Hz, 1 H), 7.10 (dd, J = 9.0, 2.4 Hz, 1 H), 6.98
(td, J = 8.4, 2.4 Hz, 1 H), 0.37 (s, 9 H) ppm. 13C NMR: δ = 164.8
(s), 162.3 (s), 136.8 (d, J = 8 Hz), 134.2 (s), 116.8 (d, J = 23 Hz),
113.2 (d, J = 19 Hz), –0.8 (s, 3 C) ppm. C9H12ClFSi (202.73): calcd.
C 53.32, H 5.97; found C 53.18, H 5.96.
1,4-Epoxy-1,4-dihydro-1-trimethylsilyl-5-fluoronaphthalene (4a): At
dry ice temperature, butyllithium (10 mmol) in hexanes (7.0 mL)
was added to a solution of 1,3-difluorobenzene (0.98 mL, 1.1 g,
10 mmol) and undecane (1.0 g) in tetrahydrofuran (20 mL). After
15 min at –75 °C, the white suspension was transferred through
Teflon tubing into excess 2-(trimethylsilyl)furan (4.0 mL, 3.5 g,
25 mmol) kept at +50 °C. The mixture was washed with water
(50 mL) and separated. According to gas chromatography (30 m,
DB-1, 100 °C; 30 m, DB-WAX, 100 °C; undecane as the “internal
standard” for quantification), the organic layer contained 1,4-ep-
oxy-1,4-dihydro-1-trimethylsilyl-5-fluoronaphthalene (4a) and 1,4-
epoxy-1,4-dihydro-1-trimethylsilyl-8-fluoronaphthalene (4b) in
17% and 8% yield, respectively. As these compounds decomposed
upon attempted separation and purification by column or prepara-
tive gas chromatography, the structures are only tentatively as-
signed. 1H NMR (of the mixture of isomers 4a and 4b): δ = 7.0
(m, 1 H), 6.7 (m, 2 H), 6.41 (dd, J = 3.0, 1.5 Hz, 0.33 H), 5.98 (dd,
J = 2.5, 1.8 Hz, 0.67 H), 0.33 (s, 0.33×9 H), 0.32 (d, J = 1.3 Hz,
0.67×9 H) ppm.
2-(Trimethylsilyl)furan: Butyllithium (0.25 mol) in hexanes (0.15 L)
was transferred into a solution of furan (18 mL, 17 g, 0.25 mol)
and N,NЈ,NЈ,NЈЈ,NЈЈ-pentamethyldiethylenetriamine (52 mL, 43 g,
0.25 mol) in the course of 15 min at 25 °C. At 0 °C, excess chloro-
trimethylsilane (50 mL) was added all at once to the white suspen-
sion. Direct distillation afforded a colorless oil. Yield: 20.5 g (58%).
B.p. 50–52 °C/50 Torr. n2D0 = 1.4430 (ref.[29]: n2D0 = 1.447). 1H NMR:
δ = 7.66 (d, J = 1.5 Hz, 1 H), 6.64 (d, J = 3.2 Hz, 1 H), 6.40 (dd,
J = 3.2, 1.5 Hz, 1 H), 0.29 (s, 9 H) ppm.
1,4-Epoxy-1,4-dihydronaphthalenes
1,4-Epoxy-1,4-dihydro-5-fluoronaphthalene
(1):
Butyllithium
(0.10 mol) in hexanes (70 mL) was added to a solution of 1,3-di-
fluorobenzene (9.9 mL, 11 g, 0.10 mol) in tetrahydrofuran (0.10 L)
at –75 °C. After 15 min, the white suspension was transferred
through Teflon tubing into furan (73 mL, 68 g, 1.0 mol) kept at
+25 °C. The reaction mixture was diluted with hexanes (0.25 L)
and filtered through a pad of alumina. After evaporation of the
solvents, the residue was distilled. A slightly yellow oil was ob-
tained. Yield: 7.30 g (45%). B.p. 57–58 °C/1 Torr. 1H NMR: δ =
7.0 (m, 3 H), 6.96 (symm. m, 1 H), 6.68 (td, J = 8.3, 0.6 Hz, 1 H),
5.97 (br. s, 1 H), 5.74 (br. s, 1 H) ppm. 13C NMR: δ = 157.1 (s),
154.6 (s), 152.7 (d, J = 5 Hz), 142.8 (d, J = 55 Hz), 133.6 (d, J =
21 Hz), 127.6 (d, J = 6 Hz), 116.3 (d, J = 3 Hz), 113.8 (d, J =
22 Hz), 82.5 (d, J = 1 Hz), 79.4 (d, J = 1 Hz) ppm. C10H7FO
(162.05): calcd. C 74.07, H 4.35; found C 74.01, H 4.21.
1,4-Epoxy-1,4-dihydro-1-trimethylsilyl-5-chloronaphthalene (5a): In
an analogous manner to that described for compounds 4a and 4b,
starting from 1,3-dichlorobenzene (1.1 mL, 1.5 g, 10 mmol) instead
of 1,3-difluorobenzene, 1,4-epoxy-1,4-dihydro-1-trimethylsilyl-5-
chloronaphthalene (5a) and 1,4-epoxy-1,4-dihydro-1-trimethylsilyl-
8-chloronaphthalene (5b) were formed in 15% and 8% yield,
1
respectively. H NMR (of the mixture of isomers 5a and 5b): δ =
7.0 (m, 1 H), 6.9 (m, 2 H), 5.87 (dd, J = 1.8, 1.0 Hz, 0.33 H), 5.71
(d, J = 1.8 Hz, 0.67 H), 0.35 (s, 0.67×9 H), 0.30 (s, 0.33×9 H)
ppm.
1,4-Epoxy-1,4-dihydro-1-trimethylsilyl-5-fluoro-8-(trimethylsilyl)-
naphthalene (6): A solution of 2-chloro-4-(fluorophenyl)trimethyl-
silane (5.1 g, 25 mmol) and butyllithium (25 mmol) in tetra-
hydrofuran (50 mL) was kept at –75 °C for 2 h, before excess 2-
(trimethylsilyl)furan (8.0 mL, 7.0 g, 50 mmol) was added all at
1,4-Epoxy-1,4-dihydro-5-(trimethylsilyl)naphthalene (2): (2-Fluo-
rophenyl)trimethylsilane (8.4 g, 50 mmol) was added dropwise to a
4404
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2005, 4401–4405