Practical Intermolecular Hydroarylation of Diverse Alkenes via Reductive Heck Coupling

We report a palladiumcatalyzed reductive Heck hydroarylation of unactivated and heteroatom-substituted terminal alkenes with an array of aryl iodides

John A. Gurak; Keary M. Engle


Scholarcy highlights

  • The hydroarylation of alkenes is an attractive approach to construct carbon–carbon bonds from abundant and structurally diverse starting materials
  • Reductive Heck hydroarylation involves intercepting the alkylpalladium(II) intermediate that is generated upon migratory insertion with a hydride source, most commonly formate
  • This transformation has been investigated since the early 1980s, and pioneering work by Cacchi and others during this period led to effective protocols with several classes of C– C-π-bondcontaining substrates that lack β-H atoms or that form stabilized π-allyl/π-benzyl/ enolate intermediates, including strained alkenes, α,β-enones/enals, alkynes, tethered alkenes, and styrenes
  • Buchwald has described a CuH/Pd dual catalytic system for anti-Markovnikov hydroarylation of terminal alkenes with aryl bromides and electron-poor aryl chlorides.. To complement this approach, we became interested in developing a general monometallic reductive Heck protocol that would be operationally simple, employ readily available reaction components, and exhibit broad functional group compatibility, which motivated the present study
  • While this manuscript was in preparation, a related catalytic system for reductive Heck coupling of alkenes with aryl bromides was reported
  • The initial sequence of events follows that of the Mizoroki-Heck reaction: oxidative addition of the aryl iodide, alkene coordination, and migratory insertion of the aryl group to give the alkylpalladium(II) intermediate
  • The reaction provides predominantly the anti-Markovnikov product and is compatible with a wide variety of synthetically important functional groups, including many that are reductively labile

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