Density functional theory calculations (B3LYP and M06) have been utilized to study a newly reported Heck-type reaction that uses an allylic or alkenyl alcohol as substrate and palladium as catalyst in the form of a chelate with a chiral pyridine oxazoline (PyrOx) ligand. The reaction not only controls the regio-and enantioselectivities of arylation of the C=C bond, but also forms the carbonyl functionality up to four bonds away from the aryl substituent. Computations performed on representative reaction systems allow us to propose a detailed mechanism with several key steps. Initial oxidation of palladium(0) by aryldiazonium generates active arylpalladium(II) species that bind the C=C bond of an allylic or alkenyl alcohol. The activated C=C bond inserts into the palladium�aryl moiety to attain aryl substitution and a chiral carbon center, and the resulting complex undergoes �-hydride elimination to give a new C=C bond that can repeat the insertion/elimination process to move down the carbon chain to form an enol that tautomerizes to a highly stable carbonyl final product. The mechanism explains the C=C bond relay and elucidates the origins of the regio- and enantioselectivities.

Mechanism of a palladium-catalyzed unprecedented Heck relay reaction: Insight into the origins of regio- and enantioselectivities

247th National Meeting (2014)

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