Regio- and enantiospecific rhodium-catalyzed arylation of unsymmetrical fluorinated acyclic allylic carbonates: inversion of absolute configuration.
The transition metal-catalyzed allylic substitution with unstabilized carbon nucleophiles represents an important cross-coupling reaction for the construction of ternary carbon stereogenic centers. We have developed a new regio- and enantiospecific rhodium-catalyzed allylic alkylation of acyclic unsymmetrical chiral nonracemic allylic alcohol derivatives with aryl zinc bromides. This study demonstrates that the hydrotris(pyrazolyl)borate rhodium catalyst and zinc(II) halide salt are crucial for efficiency, while the addition of lithium bromide to the catalyst is necessary for obtaining optimal regiospecificity. The stereochemical course of this reaction was established through the synthesis of (S)-ibuprofen, which demonstrated that the alkylation proceeds with net inversion of absolute configuration consistent with direct addition of the nucleophile to the metal center followed by reductive elimination.
Evans
P Andrew
PA
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA. paevans@indiana.edu
Uraguchi
Daisuke
D
D000478:Alkylation; D000498:Allyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D001555:Benzene Derivatives / Q000138:chemical synthesis / Q000737:chemistry*; D002254:Carbonates / Q000138:chemical synthesis / Q000737:chemistry*; D002384:Catalysis; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry; D020005:Propanols / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D013237:Stereoisomerism; D015032:Zinc / Q000737:chemistry
D000498:Allyl Compounds; D001555:Benzene Derivatives; D002254:Carbonates; D006845:Hydrocarbons, Fluorinated; D009942:Organometallic Compounds; D020005:Propanols; C006463:allyl alcohol; D012238:Rhodium; D015032:Zinc