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Under the optimal conditions, we explored the enan-
tioselective conjugated addition reaction of cyclic enones
with Cu(acac)2 at different temperature (Table 3). When
cyclopentenone was used as substrate, the enantioselec-
tivity was quite low. The catalytic activity was gently
improved when the temperature was risen (entries 1–4).
Addition of Et2Zn to cyclohexenone with Cu(acac)2 could
obtain better catalytic activity and enantioselectivity. The
highest ee reached 76% with 99% yield at -15 °C (entries
5–8). However, for 2-cycloheptenone the catalytic activity
was moderate despite enhancing the reaction temperature,
and the optimal enantioselectivity was 73% below 0 °C
(entries 8–10). The ee value was reduced with enhancing
the reaction temperature (entries 11, 12).
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4 Conclusion
In conclusion, we have developed a new family of chiral
P/S ligands L1, L2 and L4. Good reactivities and moderate
enantioselectivities were obtained in the Pd-catalyzed
allylic substitution with L1 and Cu-catalyzed conjugated
additions of cyclic enones with L2. Further investigation of
other P/S ligands applied in asymmetric catalytic reactions
is underway.
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Acknowledgements This work was financially supported by the
Hunan Provincial Key Laboratory of Materials Protection for Electric
Power and Transportation (Changsha University of Science &
Technology), and Changsha University of Science & Technology.
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