- 追加された行はこの色です。
- 削除された行はこの色です。
**Silaborative C-C Coupling Reaction
Silylboranes, 1,3-dienes, and aldehydes are coupled in the presence of a platinum catalyst [Ref. 1]. The reaction provided '''O'''-silylated homoallylic alcohols with high stereoselectivities for the '''syn'''-stereoisomers. The three-component coupling may involve σ-allylplatinum species as a key reactive interemediate.
#ref(Graphics for Reserch/silaborative C-C coupling.jpg,center)
With recognition of the importance of direct catalytic C-H functionalization for the development of “green” production processes, we also make efforts to the development of new C-H functionalization reactions.
**4.1. Catalytic Addition of C-H Bond to C=C Bonds [#s3bda7a7]
We are particularly interested in the addition of alkyne-C–H bond to C=C bonds, which has been unexplored. In the presence of nickel catalysts, additions of terminal alkyne to 1,3-dienes, styrenes, and methylenecyclopropanes were developed (J. Am. Chem. Soc. 2008, J. Am. Chem. Soc. 2009). The hydroalkynylation of 1,3-dienes has been extended to asymmetric catalysis with up to 93% ee (Angew. Chem., Int. Ed. 2010). Moreover, one step conversion of a variety of aldehydes into γ,δ-unsaturated ketones has been accomplished by nickel catalyzed hydroacylation of methylenecyclopropanes (J. Am. Chem. Soc. 2009).
#ref(hydroalkynylation(rev).jpg,center,120%)
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**Catalytic Hydroalkynylation
The C-H bonds of terminal alkynes are known to add not only to alkynes (homo- and cross-dimerization), but also to highly reactive C=C bonds in allenes, cyclopropenes, and norbornadiene. However, no reaction systems have been established for hydroalkynylation of less reactive C=C bonds. We found that the alkyne C–H bond adds to a carbon-carbon double bond of 1,3-dienes, styrenes, and norbornene at room temperature in the presence of a nickel catalyst in regio- and stereoselective manners [Ref. 2].
#ref(Graphics for Reserch/hydroalkynylation.jpg,center)
#ref(hydroalkynylation(asym).jpg,center,120%)
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**Related Researches
-Intramolecular Cyanoboration
**4.2. Removable o-Directing Group for Organoboronic Acids [#d3abaf99]
We are also interested in directed C-H activation in which directing groups play key roles in the enhancement of reaction rate as well as regioselectivity. We have recently established easily attachable and removable directing group for arylboronic acids. 2-Pyrazol-5-ylaniline efficiently undergoes condensation with arylboronic acids, giving ArB(pza) derivatives as shown in the following scheme (J. Am. Chem. Soc. 2009). The pza group serves as an ortho-directing group in the ruthenium catalyzed o-C–H silylation. This is the first demonstration of the attachment of directing group on the easily convertible substituents such as a boronyl group. We recently established more efficient removable directing group, AAM (anthranilamide) (Org. Lett. 2011).
**4.3. C-H Activation at the Methyl Groups on Silicon [#ha6b9149]
More recently, we established selective C-H borylation of methyl groups on the silicon atom (J. Am. Chem. Soc. 2012). In spite of the steric bulkiness of the silyl groups, the methyl group on silicon is selectively converted to borylmethyl groups, of which the boryl group serve as convenient handle for further transformation. This new C-H borylation allowed us to functionalize chloromethylsilanes, which are major starting materials in silicone industry produced by the Rochow direct process, being recognized as the first catalytic process in which the methyl groups of the chloromethylsilanes are converted selectively, leaving the chlorine on the silicon atom intact. Highly inert tetramethylsilane also undergoes the C-H borylation at its methyl group.
#ref(C-H borylation.jpg,center,120%)
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#ref(Graphics for Reserch/intramol. cyanoboration80.jpg,center)
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-Cyanoboration
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#ref(Graphics for Reserch/cyanoboration80.jpg,center)
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-Alkynylboration
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#ref(Graphics for Reserch/alkynylboration80.jpg,center)
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-Transmetallative Cyclizative Carboboration
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#ref(Graphics for Reserch/transmetallative cyclizative carboboration80.jpg,center)
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-Transmetallative Three-Component Carboboration
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#ref(Graphics for Reserch/transmetallative three-component carboboration80.jpg,center)
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-Module-Based Iterative Cross-Coupling
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#ref(Graphics for Reserch/concept of boron masking80.jpg,center)
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-Asymmetric Polymerization
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#ref(Graphics for Reserch/asymmetric polymerization80.jpg,center)
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**References
-Ref. 1
--Platinum-Catalyzed Silaborative Coupling of 1,3-Dienes to Aldehydes: Regio- and Stereoselective Allylation with Dienes through Allylic Platinum Intermediates M. Suginome, H. Nakamura, T. Matsuda, Y. Ito, '''J. Am. Chem. Soc.''' ''1998'', 120, 4248-4249, [[10.1021/ja980373o>http://dx.doi.org/10.1021/ja980373o]]
-Ref. 2
--Nickel-Catalyzed Addition of C-H Bonds of Terminal Alkynes to 1,3-Dienes and Styrenes M. Shirakura, M. Suginome, '''J. Am. Chem. Soc.''' ''2008'', 130, 5410-5411, [[10.1021/ja800997j>http://dx.doi.org/10.1021/ja800997j]]
