Enantioenriched Allylic Alcohols via sp-Carbon Coupling of Allenes
S.-S. Ng, T. F. Jamison*
Massachusetts Institute of Technology, Cambridge, USA
21 September 2005 (online)
Coupling reactions involving allenes often occur with C-X bond formation at one of the sp2-hybridized carbons. When coupling ‘allenylmetals’ with aldehydes, typically homoallylic or homopropargylic alcohols are formed. This paper reports an atypical coupling at the central sp-hybridized carbon to form allylic alcohols. Using a Ni(0)/NHC-i-Pr catalyst system, allenes, aromatic aldehydes and trialkylsilanes can be coupled efficiently with complete allene chirality transfer to create a variety of allylic silyl ethers. Electron-donating or -withdrawing aromatic substituents have little effect on the yield, as does the choice of silane. Only sterically bulky allene substituents seem to greatly decrease the yield.