Use of Deuterium Labeling Studies to Determine the Stereochemical Outcome of Palladium Migrations during an Asymmetric Intermolecular Heck Reaction Bronwen M. M. Wheatley and Brian A. Keay* Department of Chemistry, UniVersity of Calgary, Calgary, Alberta, Canada, T2N 1N4
[email protected] ReceiVed May 26, 2007
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-β-H Pd eliminations during the formation of 6 and 7.
Introduction In 1997, Brown, Deeth and co-workers1 reported via lowtemperature NMR studies (-60 °C) that 5a was the first observable intermediate in the asymmetric Heck reaction between phenyl triflate (1) and 2,3-dihydrofuran (2a, Scheme 1). Subsequent warming of the solution provided 6a exclusively (
