An improved catalyst for the asymmetric arylation of ketone enolates |
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Authors: | Hamada Takayuki Chieffi André Ahman Jens Buchwald Stephen L |
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Institution: | Contribution from the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139. |
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Abstract: | A new catalyst system for the enantioselective alpha-arylation of ketones is reported. This catalyst, prepared from Pd(2)(dba)(3) and a bulky dialkylphosphino-binaphthyl ligand, is able to effect the asymmetric arylation of ketone enolates with aryl bromides utilizing NaO(t)()Bu as base. These new catalysts enjoy much higher reactivity than previous systems; arylation reactions could be effected at room temperature with only 2 mol % of the Pd catalyst. The coupling of alpha-alkyl-alpha'-protected cyclopentanones proceeded in high yield, and the resulting quaternary stereogenic center was installed in up to 94% ee. |
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