Beta-hydride elimination is one of the fundamental reactions ofalkylpalladium complexes.  Since thisreaction is reversible, consecutive beta-hydride elimination/insertion reactionsresult in a rearranged alkyl ligand, and this rearrangement has found someutility in synthesis.  However, in allexamples migration toward less sterically-hindered carbon atom occurred.  We recently discovered thatpalladium-catalyzed coupling of 3-bromoallylic alcohols (RBrCH=CHCH2OH)and 2-arylalkyltrifluoroborates (ArCH(CH3)CH2BF3K)affords a minor product with the quaternary carbon center attached directly tothe vinyl carbon (Ar(CH3)2C-C R=CH-CH2OH).  Thisproduct is apparently formed via rearrangement of a primary alkylpalladiumcomplex to the tertiary one, and, to the best of our knowledge suchrearrangement has not been reported before. Herein, we present our studies of this unusual process, and provideevidence that the driving force of this rearrangement is resonancestabilization of the alkyl-palladium bond. Effect of steric hindrance, aryl substituent, palladium complex, andhalide coupling partner on the rearrangement will be discussed.

Unusual primary to tertiary alkyl rearrangement and formation of quaternary carbon centers during the palladium-catalyzed cross-coupling of 2-arylalkyltrifluoroborate salts

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.