M. J. Dabdoub et al. / Tetrahedron Letters 42 (2001) 1595–1597
regiocontrolled process. See Ref. 4.
1597
On the other hand, it was observed that the 1-phenyl-1-
phenylseleno-2-phenylthioethane 5 underwent the Se/Li
exchange reaction when treated with butyllithium in
THF (−78°C; 30 min), leading to the corresponding
E-vinylic sulfide after treatment of the intermediate
with water (59% yield). By reacting compound 4 with
butyllithium under similar conditions we confirmed that
the Se/Li exchange reaction is less efficient than the
Te/Li exchange reaction. In this case, most of the
starting material was recovered, and the expected (E)-1-
phenylthio-1-hexene was isolated in only 38% yield.
However, in all these cases the initial geometry of the
double bonds was retained. More detailed studies on
the generation of the b-phenylthiovinyllithium interme-
diates from vinylic tellurides of types 8 and 9 and their
reactions to form carbonꢀcarbon bonds are underway
in our laboratory.
9. Takahashi, H.; Ohe, K.; Uemura, S.; Sugita, N. Nippon
Kagaku Kaishi. 1987, 1508.
10. Stefani, H. A.; Costa, I. M.; Zeni, G. Tetrahedron Lett.
1999, 40, 9215 and references cited therein.
11. Dabdoub, M. J.; Begnini, M. L.; Guerrero, Jr., P. G.;
Baroni, A. C. M. J. Org. Chem. 2000, 65, 61.
12. Silveira, C. C.; Perin, G.; Braga, A. L.; Dabdoub, M. J.;
Jacob, R. G. Tetrahedron 1999, 55, 7421.
13. Dabdoub, M. J.; Dabdoub, V. B.; Marino, J. P. Tetra-
hedron Lett. 2000, 41, 433.
14. Typical procedure: To a 100 mL flask, containing a
mixture of the appropriate 1-phenylthioacetylene (5.0
mmol), NaBH4 (0.236 g; 6.25 mmol) and 95% ethanol (25
mL) under a nitrogen atmosphere with vigorous stirring,
the appropriate dichalcogenide (2.5 mmol) in ethanol (25
mL) was added dropwise (very slowly) at rt. The dark red
color of the ditelluride or the yellow color of the dise-
lenide became colorless in the course of the addition. The
resulting solution was refluxed for the time indicated in
Table 1, then it was allowed to reach room temp., diluted
with ethyl acetate and washed with saturated aqueous
NH4Cl solution (2×) and brine (2×). The organic layer
was dried over MgSO4, filtered and concentrated using a
rotary evaporator. The product was purified by column
chromatography on silica gel (hexanes), to give the pure
compound.
In summary, we disclosed here the first highly efficient
regio- and stereocontrolled hydrochalcogenation of di-
substituted alkynes that does not contain unsaturated
conjugated groups.
Acknowledgements
This work was supported by grants from FAPESP and
CNPq. Thanks are due to Professor Antonio Gilberto
Ferreira (UFSCar) for providing NMR facilities.
15. Yang, J.; Cohn, S. T.; Romo, D. Org. Lett. 2000, 2, 763.
16. Tingoli, M.; Tiecco, M.; Testaferri, L.; Temperini, A.
Tetrahedron 1995, 51, 4691.
17. Huang, X.; Ma, Y. Chin. J. Chem. 1998, 16, 483.
18. Potapov, V. A.; Amozova, S. V. Zh. Org. Khim. 1996, 32,
1142 and references cited therein.
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8. Diisobutylaluminum tellurolate reacts with aryl or alkyl
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25. Typical procedure: To a solution of compound 9 (2.0
mmol) in THF (20 mL), BuLi (2.0 mmol) was added at
−78°C under a nitrogen atmosphere. After 15 minutes,
water was added (4.0 mL) and the product was isolated
following the usual extraction procedure.11
.
.