J.-N. Volle, M. Schlosser
FULL PAPER
Dimethyl 4-Bromo-5-(trifluoromethyl)phthalate (6): This compound
was prepared analogously with diene 5 (4.9 g, 20 mmol) and isol-
1.18 g (24%). The yield, as determined by gas chromatography (30
m, DB-FFAP, 100 °C; 30 m, DB-1701, 120 °C), increased to 38%,
ated as colorless needles (from hexanes); m.p. 24Ϫ25 °C; b.p. 52% and 60% when a twofold, fourfold and sixfold excess of cyano-
97Ϫ99 °C/0.3 Torr; yield: 3.8 g (56%). 1H NMR: δ ϭ 8.11 (s, 1 H), formate was used, respectively. The pyridine ester 4 was isolated
8.00 (s, 1 H), 3.95 (s, 3 H), 3.94 (s, 3 H). 19F NMR: δ ϭ Ϫ63.7 (s). in 45% yield (2.2 g) from the last reaction. 1H NMR: δ ϭ 8.96
MS: m/z (%) ϭ 360 (100) [M ϩ NH4ϩ], 343 (80), 342 (48) [Mϩ]. (d, J ϭ 5.1 Hz, 1 H), 8.37 (s, 1 H), 7.23 (d, J ϭ 5.1 Hz, 1 H), 4.06
C11H8BrF3O4 (341.08): calcd. C 38.74, H 2.36; found C 38.74, H
2.28.
(s, 3 H). 13C NMR: δ ϭ 164.4 (s), 150.8 (s), 149.2 (s), 139.6
(q, J ϭ 35 Hz), 122.4 (s, J ϭ 274 Hz), 122.3 (q, J ϭ 4 Hz), 120.9
(q, J ϭ 4 Hz), 53.2 (s). 19F NMR: δ ϭ Ϫ65.3 (s). MS: m/z (%) ϭ
224 (17), 223 (79) [M ϩ NH4ϩ], 207 (32), 206 (100) [Mϩ ϩ 1], 205
Dimethyl 2-Trifluoromethyl-1,1Ј-biphenyl-4,5-dicarboxylate (10):
This compound was prepared analogously with diene 9 (4.8 g,
20 mmol) and isolated as colorless starlets after chromatography (6) [Mϩ]. C8H6F3NO2 (205.14): calcd. C 46.84, 2.95; found C 46.75,
with a 1:20 (v/v) mixture of ethyl acetate and hexanes as the eluent; H 2.75.
1
m.p. 71Ϫ73 °C (from hexanes); yield: 4.9 g (72%). H NMR: δ ϭ Methyl 5-Phenyl-4-trifluoromethyl-2-pyridinecarboxylate (12): This
8.19 (s, 1 H), 7.64 (s, 1 H), 7.4 (m, 3 H), 7.3 (m, 2 H), 3.97 (s, 3
compound was prepared by reaction between the diene 9 (4.9 g,
H), 3.94 (s, 3 H). 13C NMR: δ ϭ 167.2 (s), 166.2 (s), 144.9 (s), 20 mmol) and methyl cyanoformate (1.6 mL, 1.7 g, 20 mmol),
137.8 (s), 135.4 (s), 132.4 (s), 130.6 (q, J ϭ 31 Hz), 129.9 (2 C), worked up in the same way as specified for the (trifluoromethyl)-
128.6 (s), 128.5 (2 C), 128.1 (s), 127.4 (q, J ϭ 5 Hz), 123.1 (q, J ϭ
phthalic esters above and isolated as slightly yellowish needles after
275 Hz), 53.0 (2 C). 19F NMR: δ ϭ Ϫ57.9 (s). C17H13F3O4 chromatography on silica (50 mL) with a 1:20 (v/v) mixture of ethyl
(338.28): calcd. C 60.36, H 3.87; found C 60.29, H 3.84.
acetate and hexanes as the eluent; m.p. 64Ϫ65 °C (from heptanes);
yield: 0.78 g (14%). H NMR: δ ϭ 8.79 (s, 1 H), 8.47 (s, 1 H), 7.5
1
(Trifluoromethyl)benzoic Esters
(m, 3 H), 7.4 (m, 2 H), 4.08 (s, 3 H).). 13C NMR: δ ϭ 164.6 (s),
152.9 (s), 147.6 (s), 138.9 (s), 137.0 (q, J ϭ 32 Hz), 134.8 (s), 129.1
(s), 128.9 (s, 2 C), 128.4 (s, 2 C), 123.2 (q, J ϭ 276 Hz), 121.3 (q,
J ϭ 5 Hz), 53.3 (s). 19F NMR: δ ϭ Ϫ59.8 (s). C14H10F3NO2
(281.23): calcd. C 59.79, H 3.58, N 4.98; found C 59.78, H 3.72,
N 5.00.
Methyl 4-(Trifluoromethyl)benzoate (3): Diene 1 (3.3 g, 20 mmol)
and methyl propiolate (1.7 mL, 1.7 g, 20 mmol) were mixed and
heated for 16 h at 100 °C. The reaction was worked up as described
in the preceding section; colorless liquid; b.p. 84Ϫ86 °C/9 Torr
(ref.:[12] b.p. 94.3Ϫ94.8 °C/21 Torr); yield: 3.1 g (77%). 1H NMR:
δ ϭ 8.16 (d, J ϭ 8.3 Hz, 2 H), 7.71 (d, J ϭ 8.3 Hz, 2 H), 3.96 (s,
3 H). 19F NMR: δ ϭ Ϫ63.6 (s).
Methyl 3-Bromo-4-(trifluoromethyl)benzoate (7) and Methyl 4-
Bromo-3-(trifluoromethyl)benzoate (8): According to NMR spectro-
scopy, the two compounds were obtained as a 5:1 mixture when
diene 5 (4.9 g, 20 mmol) was used under otherwise identical condi-
tions; colorless viscous liquid; b.p. 99Ϫ103 °C/4 Torr; yield: 3.8 g
(28%). 1H NMR: δ ϭ 8.39 (s, 0.85 H), 8.37 (s, 0.15 H), 8.08 (d,
J ϭ 8.3 Hz, 0.85 H), 8.06 (dd, J ϭ 8.3, 1.9 Hz, 0.15 H), 7.83 (d,
J ϭ 8.3 Hz, 0.15 H), 7.79 (d, J ϭ 8.3 Hz, 0.85 H), 3.99 (s, 2.55 H),
3.98 (s, 0.45 H). 19F NMR: δ ϭ Ϫ63.4 (s, 0.45 F), Ϫ63.6 (s, 2.55
F). C9H6BrF3O2 (283.04): calcd. C 38.19, H 2.14; found C 38.33,
H 2.16.
Methyl 2-Trifluoromethyl-1,1Ј-biphenyl-5-carboxylate (11): This
compound was prepared analogously with diene 9 (4.8 g, 20 mmol)
and isolated as a colorless liquid; b.p. 87Ϫ89 °C/0.2 Torr; yield:
4.2 g (75%). 1H NMR: δ ϭ 8.12 (d, J ϭ 8.3 Hz, 1 H), 8.01 (s, 1
H), 7.83 (d, J ϭ 8.3 Hz, 1 H), 7.4 (m, 3 H), 7.3 (m, 2 H), 3.97 (s,
3 H). 13C NMR: δ ϭ 165.8 (s), 141.8 (s), 138.8 (s), 133.1 (s), 132.8
(s), 132.1 (q, J ϭ 30 Hz), 128.9 (s, 2 C), 128.3 (s), 128.0 (s), 127.9
(s, 2 C), 126.4 (q, J ϭ 5 Hz), 123.6 (q, J ϭ 275 Hz), 52.5 (s). 19F
NMR: δ ϭ Ϫ57.8 (s). C15H11F3O2 (338.28): calcd. C 64.29, H 3.96;
found C 64.02, H 4.00.
Acknowledgments
This work was financially supported by the Schweizerische Na-
tionalfonds zur Förderung der wissenschaftlichen Forschung, Bern
(grant 20-55Ј303-98), and the Bundesamt für Bildung und Wissen-
schaft, Bern (grant 97.0083 linked to the TMR project
FMRXCT-970129).
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Methyl 4-Trifluoromethyl-2-pyridinecarboxylate (4): A solution of
1-ethoxy-3-trifluoromethyl-1,3-butadiene (1; 4.8 g, 20 mmol) and
methyl cyanoformate (1.6 mL, 1.7 g, 20 mmol) in toluene (20 mL)
was heated under reflux (to approx. 110 °C) for 24 h before the
product was absorbed on silica gel (50 mL) and eluted with a 1:3
(v/v) mixture of ethyl acetate and hexanes; colorless prisms; m.p.
29Ϫ31 °C (from hexanes at Ϫ75 °C); b.p. 87Ϫ89 °C/13 Torr; yield:
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Received November 30, 2001
[O01565]
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Eur. J. Org. Chem. 2002, 1490Ϫ1492