(CDC)-Rhodium-catalyzed hydroallylation of vinylarenes and 1,3-dienes with allyltrifluoroborates

Justin S. Marcum, Tia N. Cervarich, Rajith S. Manan, Courtney C. Roberts, Simon J. Meek

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Catalytic site-selective hydroallylation of vinyl arenes and 1,3-dienes is reported. Transformations are promoted by a readily accessible bidentate carbodicarbene-rhodium complex and involve commercially available allyltrifluoroborates and an alcohol. The reaction is applicable to vinyl arenes and aryl-or alkyl-substituted 1,3-dienes (30 examples). Allyl addition products are generated in 40-78% yield and in up to >98:2 site selectivity. Reaction outcomes are consistent with the intermediacy of a Rh(III)-hydride generated by protonation of Rh(I) by an acid. A number of key mechanistic details of the reaction are presented: (1) Deuterium scrambling into the product and starting alkene indicates reversible Rh(III)-H migratory insertion. (2) A large primary kinetic isotope effect is observed. (3) With substituted allyltrifluoroborates (e.g., crotyl-BF3K) mixtures of site isomers are generated as a result of transmetalation followed by Rh-(allyl) complex equilibration, consequently disproving outer-sphere addition of the allyl nucleophile to Rh(III)-(η3-allyl). (4) Stereochemical analysis of a cyclohexadiene allyl addition product supports a syn Rh(III)-hydride addition. (5) A Hammett plot shows a negative slope. Finally, utility is highlighted by a iodocyclization and cross metathesis.

Original languageEnglish (US)
Pages (from-to)5881-5889
Number of pages9
JournalACS Catalysis
Volume9
Issue number7
DOIs
StatePublished - May 22 2019
Externally publishedYes

Bibliographical note

Funding Information:
Financial support was provided by the NSF (CHE-1665125) and the University of North Carolina at Chapel Hill. J.S.M. is grateful for a Burroughs-Welcome fellowship from the UNC Chemistry Department. We thank the University of North Carolina's Department of Chemistry Mass Spectrometry Core Laboratory for their assistance with mass spectrometry analysis. This material is based upon work supported by the National Science Foundation under Grant No. (CHE1726291).

Funding Information:
Financial support was provided by the NSF (CHE-1665125) and the University of North Carolina at Chapel Hill. J.S.M. is grateful for a Burroughs-Welcome fellowship from the UNC Chemistry Department. We thank the University of North Carolina’s Department of Chemistry Mass Spectrometry Core Laboratory for their assistance with mass spectrometry analysis. This material is based upon work supported by the National Science Foundation under Grant No. (CHE1726291).

Keywords

  • alkene
  • allyltrifluoroborates
  • carbodicarbene ligands
  • hydroallylation
  • rhodium catalysis

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