Use of Deuterium Labeling Studies to Determine the Stereochemical Outcome of Palladium Migrations during an Asymmetric Intermolecular Heck Reaction

A series of deuterium labeling experiments showed that Pd migrations during an intermolecular asymmetric Heck reaction between phenyl triflate and various deuterated 2,3-dihydrofurans (2b, 2c, 2d, 2e) occurs exclusively by either syn-1,2-dyotropic shifts or a syn-chain-walking mechanism; no evidence was observed to support anti-1,2-dyotropic shifts or anti-beta-H Pd eliminations during the formation of 6 and 7.