Trifluoromethylthiocomanic acid
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 4, April, 2010
847
mixed with conc. HCl (100 mL). The precipitate that formed
was filtered off, washed with conc. HCl, dried, and recrystalꢀ
lized from toluene. The yield was 3.78 g (42%), light gray crysꢀ
tals, m.p. 157 °C. Found (%): C, 37.54; H, 1.24. C7H3F3O3S.
Calculated (%): C, 37.51; H, 1.35. IR, ν/cm–1: 1718, 1609, 1562,
1422. 1H NMR (DMSOꢀd6), δ: 3.00—7.00 (br.s, 1 H, OH); 7.53
(d, 1 H, H(3), J = 1.6 Hz); 7.57 (quint, 1 H, H(5), J = 1.0 Hz).
a Würtz flask. The distilled product was collected as an oily liquid
solidifying into large crystals upon cooling. The yield was 2.52 g
(80%), colorless crystals, m.p. 21 °C (cf. Ref. 2: m.p. 21—22 °C).
1H NMR (CDCl3), δ: 6.46 (dd, 1 H, H(5), J = 5.9 Hz, J = 2.5 Hz);
6.75 (d, 1 H, H(3), J = 2.5 Hz); 7.84 (d, 1 H, H(6), J = 5.9 Hz).
2ꢀDifluoromethylꢀ4Hꢀpyranꢀ4ꢀone (7b) was obtained from
acid 2b (1.5 g, 7.9 mmol) as described above for pyrone 7a. The
yield was 0.88 g (77%), light yellow crystals, m.p. 33—34 °C.
Found (%): C, 49.55; H, 2.69. C6H4F2O2. Calculated (%):
C, 49.33; H, 2.76. IR, ν/cm–1: 1625, 1269, 1188, 1130. 1H NMR
(CDCl3), δ: 6.37 (td, 1 H, CHF2, J = 53.6 Hz, J = 0.4 Hz); 6.40
(dd, 1 H, H(5), J = 5.9 Hz, J = 2.5 Hz); 6.61 (d, 1 H, H(3),
J = 2.5 Hz); 7.80 (d, 1 H, H(6), J = 5.9 Hz). 19F NMR (CDCl3),
δ: –124.9 (dd, CHF2, 2JH,F = 53.6 Hz, 4JH,F = 0.4 Hz).
4
19F NMR (DMSOꢀd6), δ: –62.9 (d, CF3, JH,F = 0.9 Hz). MS,
m/z (Irel (%)): 224 [M]+ (100), 196 [M – CO]+ (47), 179
[M – COOH]+ (98). Found: m/z 223.97516 [M]+. C7H3F3O3S.
Calculated: M = 223.97550.
2ꢀTrifluoromethylꢀ4Hꢀthiopyranꢀ4ꢀone (4a). A (solventꢀfree
thermal decarboxylation). Acid 3a (1.0 g, 4.5 mmol) was heated
on a Wood´s alloy bath (260 °C) in a Würtz flask. The distilled
product was collected as an oily liquid solidifying into colorless
crystals upon cooling. The yield was 0.66 g (82%), m.p. 38—39 °C.
B (decarboxylation in the presence of H2SO4). Acid 3a (1.5 g,
6.7 mmol) was added to 70% H2SO4 (1 mL). The resulting mixꢀ
ture was refluxed with stirring for 1 h and cooled to 20 °C. The
product was extracted with ether (20 mL), the extract was conꢀ
centrated, and the residue was recrystallized from light petroꢀ
leum. The yield was 0.85 g (71%), colorless crystals, m.p. 38.5 °C.
IR, ν/cm–1: 1630, 1270, 1188, 1147. 1H NMR (CDCl3), δ: 7.09
(dd, 1 H, H(5), J = 10.3 Hz, J = 1.7 Hz); 7.34 (dq, 1 H, H(3),
J = 1.7 Hz, J = 0.8 Hz); 7.80 (d, 1 H, H(6), J = 10.3 Hz).
19F NMR (250 MHz, CDCl3), δ: –65.0 (s, CF3). MS, m/z (Irel (%)):
180 [M]+ (100), 152 [M – CO]+ (59), 133 [M – 47]+ (30). Found:
m/z 179.98529 [M]+. C6H3F3OS. Calculated: M = 179.98567.
Ethyl 4ꢀoxoꢀ6ꢀtrifluoromethylꢀ4Hꢀthiopyranꢀ2ꢀcarboxylate
(5). Acid 3a (0.15 g, 0.7 mmol) was dissolved in ethanol (5 mL)
saturated with HCl. The resulting mixture was kept at 20 °C for
48 h and then diluted with water (20 mL). The product was
extracted with ether (20 mL), the extract was concentrated, and
the residue was recrystallized from ethanol. The yield was 0.026 g
(15%), light yellow crystals, m.p. 41—42 °C. 1H NMR (CDCl3),
δ: 1.43 (t, 3 H, Me, J = 7.2 Hz); 4.47 (q, 2 H, CH2, J = 7.2 Hz);
7.37 (m, 1 H, H(5)); 7.77 (d, 1 H, H(3), J = 1.6 Hz). 19F NMR
(CDCl3), δ: –64.8 (d, CF3, 4JH,F = 0.7 Hz).
Methyl 4ꢀoxoꢀ6ꢀtrifluoromethylꢀ4Hꢀthiopyranꢀ2ꢀcarboxylate
(6). Potassium bicarbonate (0.45 g, 4.46 mmol) and MeI (0.95 g,
6.69 mmol) were added to a stirred solution of acid 3a (0.50 g,
2.23 mmol) in acetone—water (3 : 1, 8 mL). The mixture was
kept at 20 °C for 24 h and then diluted with water (20 mL). The
product was extracted with light petroleum (25 mL), the extract
was concentrated, and the residue was recrystallized from light
petroleum. The yield was 0.12 g (23%), light yellow crystals,
m.p. 79 °C. Found (%): C, 40.19; H, 2.28. C8H5F3O3S. Calcuꢀ
lated (%): C, 40.34; H, 2.12. IR, ν/cm–1: 3080, 1740, 1656,
1602, 1576. 1H NMR (CDCl3), δ: 4.02 (s, 3 H, MeO); 7.36 (m, 1 H,
H(5)); 7.77 (d, 1 H, H(3), J = 1.7 Hz). 19F NMR (CDCl3), δ:
–64.8 (d, CF3, 4JH,F = 0.7 Hz).
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 06ꢀ03ꢀ04004ꢀ
NNIO) and the German Scientific and Technical Society
(Deutsche Forschungsgemeinschaft, Grant 436 RUS
113/901/0ꢀ1).
References
1. T. Hiyama, Organofluorine Compounds. Chemistry and Appliꢀ
cation, Springer Verlag, Berlin, 2000.
2. V. I. Tyvorskii, D. N. Bobrov, O. G. Kulinkovich, N. De
Kimpe, K. A. Tehrani, Tetrahedron, 1998, 54, 2819.
3. V. I. Tyvorskii, D. N. Bobrov, O. G. Kulinkovich, W. Aelterꢀ
man, N. De Kimpe, Tetrahedron, 2000, 56, 7313.
4. D. S. Yachevskii, D. L. Chizhov, K. I. Pashkevich, V. N.
Charushin, ARKIVOC, 2004, 11, 71.
5. V. I. Tyvorskii, D. N. Bobrov, O. G. Kulinkovich, K. A.
Tehrani, N. De Kimpe, Tetrahedron, 2001, 57, 2051.
6. D. S. Yachevskii, D. L. Chizhov, V. N. Charushin, Zh. Org.
Khim., 2006, 42, 148 [Russ. J. Org. Chem. (Engl. Transl.),
2006, 42, 142].
7. B. I. Usachev, I. A. Bizenkov, V. Ya. Sosnovskikh, Izv. Akad.
Nauk, Ser. Khim., 2007, 537 [Russ. Chem. Bull., Int. Ed.,
2007, 56, 558].
8. N. G. Rule, M. R. Detty, J. E. Kaeding, J. A. Sinicropi,
J. Org. Chem., 1995, 60, 1665.
9. C. H. Chen, G. A. Reynolds, B. C. Cossar, J. Org. Chem.,
1981, 46, 2752.
10. C. H. Chen, J. J. Doney, G. A. Reynolds, J. Org. Chem.,
1981, 46, 4604.
11. N. W. Boaz, K. M. Fox, J. Org. Chem., 1993, 58, 3042.
2ꢀTrifluoromethylꢀ4Hꢀpyranꢀ4ꢀone (7a). Acid 2a (4.0 g,
19.2 mmol) was heated on a Wood´s alloy bath (260 °C) in
Received February 5, 2009;
in revised form November 24, 2009