We describe a method for the site-selective construction of a C(aryl)-C(sp3) bond by the palladium-catalyzed direct allylation of arenes with allylic pivalates in the presence of AgOPiv to afford the linear (E)-allylated arene with excellent regioselectivity; this reaction occurs with arenes that have not undergone site-selective and stereoselective direct allylation previously, such as monofluorobenzenes and non-fluorinated arenes. Mechanistic studies indicate that AgOPiv ligated by a phosphine reacts with the arene to form an arylsilver(I) species, presumably through a concerted metalation-deprotonation pathway. The activated aryl moiety is then transferred to an allylpalladium(II) intermediate formed by oxidative addition of the allylic pivalate to the Pd(0) complex. Subsequent reductive elimination furnishes the allyl-aryl coupled product. The aforementioned proposed intermediates, including an arylsilver complex, have been isolated, structurally characterized, and determined to be chemically and kinetically competent to undergo the proposed elementary steps of the catalytic cycle.
Bibliographical noteFunding Information:
This work was supported by the Director, Office of Science, of the U.S. Department of Energy under contract no. DE-AC02-05CH11231 and the National Institutes of Health (postdoctoral fellowship to S.Y.L.: F32-GM113404). We thank Dr. Antonio DiPasquale for X-ray crystallographic analysis (NIH Shared Instrumentation Grant S10-RR027172) and Thomas J. OConnor (supported by UC Berkeley Amgen Scholars program and CENTC program) for assistance on the initial investigation.
© 2016 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry