JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Silylation of α,β-Unsaturated Carbonyls
also found to be suitable substrates besides mono-
substituted chalcones (3g–3h). Silylation of α,β-unsaturated
ketones having aliphatic–aromatic structures gave compa-
rable results as chalcone derivatives under the optimized
conditions (3i, 3j). Methyl- and ethyl-esters, which exhib-
ited low reactivity in a previous report,10 have shown great
improvements by using our newly developed method (3k,
3L). It is noteworthy that even cyclic α,β-unsaturated
ketones with six- and five-membered rings could be suc-
cessfully applied, yielding the corresponding organosilicon
products in 94 and 92% yield, respectively. It was also
found that the catalyst was reactive toward
α,β-unsaturated nitrile to achieve the β-silyl nitrile com-
pound, which could serve as versatile synthon for organic
synthesis.
Comparing with α,β-unsaturated substrates,
silyl conjugate additions to acyclic or cyclic
α,β,γ,δ-unsaturated dienones will be more challenging
because both site selectivity and (E)–(Z) configuration
must be taken into consideration. First, acyclic die-
nones 4a and 4b were tested under optimal conditions,
and to our delight 1,4-addtion products were selectively
observed and isolated in good yield (Scheme 1(a)).
Next, when cyclic dienones 4c and 4d were employed as
substrates, the majority of the 1,6-addition products 5c
and 5d were obtained because of thermodynamic con-
vergence8c,11 (Scheme 1(b)). This has offered an impor-
tant and efficient strategy for the synthesis of carbonyl-
containing allylsilanes.
In order to confirm the utility of our developed
method, carbonyl-containing β-silyl product 3a and
allylsilane 5d were further oxidized to give the corre-
sponding hydroxyl compounds by the well-known
Fleming–Tamao oxidation15 (Scheme 2). The silicon
substituent of the products could be recognized as the
protected group, which can be easily converted to a
hydroxyl group. This kind of approach has provided an
alternative strategy to introduce a hydroxyl group into
the complicated structure of natural products and also
a convenient pathway to protect a specific position by
the dimethylphenylsilyl group.
α,β-unsaturated ketones, esters, and nitrile could be
applied under the optimized conditions. Besides,
α,β,γ,δ-unsaturated acyclic and cyclic dienones could
also undergo silylation successfully to give the corre-
sponding 1,4- and 1,6-addition products, respectively.
Moreover, conversions from silyl products to
hydroxyl compounds were explored for the practical
application of this method
ACKNOWLEDGMENTS
This work was supported by the National Natural
Science Foundation of China (No. 21304032), the Nat-
ural Science Foundation of Hubei Province of China
(No. 2016CFB104, 2015CFC772), and the Hubei Pro-
vincial Department of Education Science and Technol-
ogy Research Projects (No. Q20162705).
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CONCLUSIONS
In conclusion, we have demonstrated that the
silylation of α,β-unsaturated acceptors can be
achieved by using basic copper carbonate as catalyst
and 2,2-bibyridine as ligand. Various substituted
J. Chin. Chem. Soc. 2017
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