L. Lebarillier et al. / Tetrahedron 56 (2000) 7495–7502
7501
yield), separated by silica gel chromatography (elution:
light petroleum/CH2Cl2: 70/30).
rated and the residue was stirred for 3 h in chloroform. After
concentration, the crude product was purified as above.
Ethyl 2-chloro-3-phenylselanylpropanoate 16a. (38%
yield) H NMR d: 7.50–7.56 (2H, m), 7.23–7.37 (3H, m),
4.30 (1H, m), 4.16 (2H, q, J7.0 Hz), 3.17–3.42 (2H, m),
1.27 (3H, t, J7.0 Hz). 13C NMR d: 167.2, 133.9, 129.2,
128.0, 126.2, 62.1, 54.7, 30.4, 13.9.
Method B: Chlorination of b-chloro-a-phenylselanyl esters
5. A solution of N-chlorosuccinimide (0.137 g, 1 mmol) and
ester 17 (1 mmol) in CCl4 (15 ml) was heated at reflux for
2 h under stirring. After cooling, the mixture was filtered on
celite, then rinsed with the same solvent (3×5 ml). The
organic solution was dried and evaporated under reduced
pressure. The oily residue was chromatographed on silica
gel with chloroform as eluent.
1
Ethyl 3-chloro-2-phenylselanylpropanoate 5a. (40%
1
yield) H NMR d: 7.56–7.62 (2H, m), 7.22–7.36 (3H, m),
4.20 (1H, d, J7.2 Hz), 4.13 (1H, d, J7.2 Hz), 3.72–3.92
(3H, m), 1.23 (3H, t, J7.0 Hz). 13C NMR d: 170.0, 136.0,
129.2, 126.1, 61.5, 43.7, 43.4, 13.9.
Ethyl 2,3-dichloro-2-phenylselanylpropanoate 22a. (51%
yield, method B). 1H NMR d: 7.65–7.70 (2H, m), 7.30–7.45
(3H, m), 4.16 (2H, m), 4.11 (1H, J11.5 Hz), 3.97 (1H, d,
J11.5 Hz), 1.21 (3H, t, J7.0 Hz). 13C NMR d: 166.1,
137.8, 130.4, 129.1, 125.8, 67.2, 63.1, 50.6, 13.6. MS:
Mϩ326. Anal. Calcd for C11H12O2Cl2Se: C, 40.51; H,
3.71. Found: C, 40.58; H, 3.88.
Ethyl 2,3-dichloro-3-phenylpropanoate 1724
Ethyl cinnamate (0.176 g, 1 mmol) was added to PhSeCl
(0.384 g, 2 mmol) and ZnCl2 (0.137 g, 1 mmol) in benzene
(10 ml). The mixture was heated on reflux for 17 h, washed
three times with water, dried and evaporated under reduced
pressure. The oily residue was purified by silica gel chro-
matography (elution: light petroleum/CH2Cl2: 70/30).
Compound 17 was obtained in 65% yield (63/37 erythro/
threo mixture of diastereoisomers).
Ethyl 2,3-dichloro-2-phenylselanylbutanoate 22b. (94%
yield, method A, 46/54 diast. ratio; 78% yield, method B,
1
40/60 diast. ratio). H NMR: A diast.: 7.67–7.72 (2H, m),
7.350–7.45 (3H, m), 4.83 (1H, q, J6.4 Hz), 3.91 (2H, m),
1.56 (3H, d, J6.4 Hz), 1.06 (3H, t, J7.1 Hz). B diast.:
7.60–7.65 (2H, m), 7.30–7.45 (3H, m), 4.79 (1H, q,
J6.6 Hz), 4.02 (2H, m), 1.86 (3H, d, J6.6 Hz), 1.11
(3H, t, J7.0 Hz). 13C NMR (CDCl3) d: A diast.: 165.9,
137.2, 130.2, 128.7, 126.5, 74.5, 62.5, 61.8, 21.1, 13.4. B
diast.: 165.9, 137.2, 130.2, 128.9, 126.4, 74.5, 62.5, 60.4,
20.5, 13.4. Anal. Calcd for C12H14O2Cl2Se: C, 42.38; H,
4.15. Found: C, 42.07; H, 4.10.
Erythro: 1H NMR, d: 7.37 (5H, m), 5.16 (1H, d,
J10.7 Hz), 4.58 (1H, d, J10.7 Hz), 4.33 (2H, q,
J7.1 Hz), 1.35 (35, t, J7.1 Hz). 13C NMR, d: 167.2,
136.2, 128.5, 127.9, 126.6, 62.2, 60.9, 58.8, 13.7.
1
Threo: H NMR, d 7.37 (5H, m), 5.27 (1H, d, J8.6 Hz),
4.63 (1H, d, J8.6 Hz), 4.03 (2H, q, J7.1 Hz), 1.05 (3H, t,
J7.1 Hz). 13C NMR, d: 166.3, 136.4, 129.2, 128.5, 127.9,
63.4, 62.4, 60.9, 13.5.
Ethyl 2,3-dichloro-2-phenylselanylhexanoate 22d. (92%
yield, method A, 60/40 diast. ratio; 45% yield, method B,
27/73 diast. ratio): 1H NMR d: A diast.: 7.64–7.73 (2H, m),
7.25–7.40 (3H, m), 4.70 (1H, dd, J0.8, 9.0 Hz), 3.88 (2H,
m), 1.30–2.10 (4H, m), 0.85–1.15 (6H, m). B diast.: 7.58–
7.68 (2H, m), 7.30–7.45 (3H, m), 4.57 (1H, dd, J1.0,
11 Hz), 4.00 (2H, m), 2.30 (1H, m), 1.30–2.10 (3H, m),
0.85–1.15 (6H, m). 13C NMR d: A and B diast. mixture:
166.0, 137.4, 130.2, 130.0, 128.9, 128.7, 74.9, 67.0, 65.9,
62.7, 36.8, 35.5, 19.6, 13.5, 13.2, 13.0. Anal. Calcd for
C14H18O2Cl2Se: C, 45.67; H, 4.93. Found: C, 45.23; H, 4.87.
Reaction of ethyl cyclohexylideneacetate with PhSeCl
Ethyl cyclohexylideneacetate 15f (0.168 g, 1 mmol)
dissolved in CH2Cl2 (10 ml) containing ZnCl2 (0.137 g,
1 mmol) was treated with PhSeCl (0.384 g, 2 mmol). The
mixture was stirred at room temperature for 10 h. The solu-
tion was washed with water (3×10 ml), dried, evaporated
under reduced pressure. The oily residue was purified by
silica gel chromatography (elution: light petroleum/
CH2Cl2: 70/30). The chloroester 20 was isolated as an oil.
The stereochemistry was not assigned.
Ethyl chloro (1-chlorocyclohexyl) phenylselanylacetate
1
22f. (94% yield, method A). H NMR d: 7.65–7.70 (2H,
m), 7.18–7.45 (3H, m), 4.01 (2H, m), 2.73 (1H, m), 2.48
(1H, m), 1.95–2.20 (2H, m), 1.60–1.85 (6H, m), 1.11 (3H, t,
J7.2 Hz). 13C NMR d: 166.9, 138.0, 130.0, 128.6, 82.7,
79.8, 62.7, 36.4, 36.3, 24.5, 22.2, 13.5. Anal. Calcd for
C16H20O2Cl2Se: C, 48.75; H, 5.11. Found: C, 48.72; H, 5.08.
Ethyl (2-chlorocyclohexylidene)acetate 20. (51% yield).
1H NMR d: 5.87 (1H, s), 4.52 (1H, m), 4.13 (2H, q,
J7.2 Hz), 3.01–3.15 (1H, m), 2.74–2.90 (1H, m), 1.35–
2.10 (6H, m), 1.25 (3H, t, J7.2 Hz). 13C NMR d: 165.1,
157.5, 114.6, 62.8, 59.2, 36.7, 26.3, 25.1, 21.2, 16.2 IR
(cmϪ1): 1718, 1609. MS: Mϩ202–204. Anal. Calcd for
C10H15O2Cl: C, 59.25; H, 7.46. Found: C, 58.96; H, 7.62.
References
a,b-Dichloro-a-phenylselanyl esters 22
1. Lebarillier, L.; Outurquin, F.; Paulmier, C. Tetrahedron, 2000,
56, 7483.
Method A: Decomposition of dichloro-adducts derived from
esters 4. Sulfuryl chloride (0.135 g, 1 mmol) was added to
ester 4 (1 mmol) dissolved in cold hexane and the mixture
was stirred for 15 min at Ϫ40ЊC. The solvent was evapo-
2. (a) Caracciolo Torchiarolo, G.; D’Onofrio, F.; Margarita, R.;
Parlanti, L.; Piancatelli, G.; Bella, M. Tetrahedron 1998, 54,
15657. (b) D’Onofrio, F.; Parlanti, L.; Piancatelli, G. Tetrahedron
Lett. 1995, 36, 1929.