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DOI: 10.1055/s-2007-968766
Catalytic Desymmetrization of 1,4-Cyclohexadienyltriisopropoxysilane
Contributor(s):Hisashi Yamamoto, Joshua N. PayetteWestfälische Wilhelms-Universität, Münster, Germany
Desymmetrization of 1,4-Cyclohexadienyltriisopropoxysilane Using Copper Catalysis
Org. Lett. 2007, 9: 2175-2178
Publication History
Publication Date:
24 July 2007 (online)
Key words
desymmetrization - copper - allylsilanes
Significance
The authors report the first catalytic desymmetrization of an allylsilane species using a chiral Cu(I) complex. Previously, the authors employed a stoichiometric chiral Ti(IV) complex to effect the desymmetrization of various 1,4-cyclohexadienes (Angew. Chem. Int. Ed. 2004, 43, 313). The current catalytic system accommodates a broad range of aromatic aldehydes including furyl and thienyl substituents. The mechanism is suggested to involve initial transmetallation of 1 to give the reactive allyl metal species 3 which via a six-membered chair transition state (6) and subsequent hydrolysis gives syn- 2.
Comment
The current methodology expands the scope of catalytic desymmetrizations to the field of allylsilane chemistry. In addition to its high substrate tolerance, the reaction can be conducted in wet solvent without affecting the yield or selectivity. The authors found that CuOTf gave similar results to Cu(OTf)2 and therefore believe that the Cu(II) salt is reduced in situ by the phosphine ligands. Interestingly, the yield could be increased nearly two-fold by changing from methanol to trifluoroethanol, presumably by increasing the rate of hydrolysis of 4.