Two flavors of PEPPSI-IPr: Activation and diffusion control in a single NHC-ligated Pd catalyst?

Igor Larrosa; Clara Somoza; Alexandre Banquy; Stephen M. Goldup

doi:10.1021/ol1027283

Two flavors of PEPPSI-IPr: Activation and diffusion control in a single NHC-ligated Pd catalyst?

Igor Larrosa^*, Clara Somoza, Alexandre Banquy, Stephen M. Goldup

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

54 Citations (Scopus)

Abstract

Abnormal reactivity has been observed in Negishi, Suzuki-Miyaura, and Kumada-Tamao-Corriu cross-couplings in which PEPPSI-IPr (where PEPPSI stands for pyridine enhanced precatalyst preparation, stabilization, and initiation and IPr refers to the NHC ligand) is employed, implicating the presence of two distinct Pd⁰ species in the catalytic cycle. Polybrominated arenes and organometallic reagents react selectively to give the product of exhaustive polysubstitution regardless of the initial reaction stoichiometry. Competition experiments suggest that, after an initial activation controlled oxidative addition, reductive elimination produces an ultrareactive Pd⁰ species which consumes all remaining C-Br bonds in the molecule under diffusion control.

Original language	English
Pages (from-to)	146-149
Number of pages	4
Journal	Organic Letters
Volume	13
Issue number	1
DOIs	https://doi.org/10.1021/ol1027283
Publication status	Published - 7 Jan 2011

ASJC Scopus subject areas

Biochemistry
Physical and Theoretical Chemistry
Organic Chemistry

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title = "Two flavors of PEPPSI-IPr: Activation and diffusion control in a single NHC-ligated Pd catalyst?",

abstract = "Abnormal reactivity has been observed in Negishi, Suzuki-Miyaura, and Kumada-Tamao-Corriu cross-couplings in which PEPPSI-IPr (where PEPPSI stands for pyridine enhanced precatalyst preparation, stabilization, and initiation and IPr refers to the NHC ligand) is employed, implicating the presence of two distinct Pd0 species in the catalytic cycle. Polybrominated arenes and organometallic reagents react selectively to give the product of exhaustive polysubstitution regardless of the initial reaction stoichiometry. Competition experiments suggest that, after an initial activation controlled oxidative addition, reductive elimination produces an ultrareactive Pd0 species which consumes all remaining C-Br bonds in the molecule under diffusion control.",

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AU - Larrosa, Igor

AU - Somoza, Clara

AU - Banquy, Alexandre

AU - Goldup, Stephen M.

PY - 2011/1/7

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N2 - Abnormal reactivity has been observed in Negishi, Suzuki-Miyaura, and Kumada-Tamao-Corriu cross-couplings in which PEPPSI-IPr (where PEPPSI stands for pyridine enhanced precatalyst preparation, stabilization, and initiation and IPr refers to the NHC ligand) is employed, implicating the presence of two distinct Pd0 species in the catalytic cycle. Polybrominated arenes and organometallic reagents react selectively to give the product of exhaustive polysubstitution regardless of the initial reaction stoichiometry. Competition experiments suggest that, after an initial activation controlled oxidative addition, reductive elimination produces an ultrareactive Pd0 species which consumes all remaining C-Br bonds in the molecule under diffusion control.

AB - Abnormal reactivity has been observed in Negishi, Suzuki-Miyaura, and Kumada-Tamao-Corriu cross-couplings in which PEPPSI-IPr (where PEPPSI stands for pyridine enhanced precatalyst preparation, stabilization, and initiation and IPr refers to the NHC ligand) is employed, implicating the presence of two distinct Pd0 species in the catalytic cycle. Polybrominated arenes and organometallic reagents react selectively to give the product of exhaustive polysubstitution regardless of the initial reaction stoichiometry. Competition experiments suggest that, after an initial activation controlled oxidative addition, reductive elimination produces an ultrareactive Pd0 species which consumes all remaining C-Br bonds in the molecule under diffusion control.

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Two flavors of PEPPSI-IPr: Activation and diffusion control in a single NHC-ligated Pd catalyst?

Abstract

ASJC Scopus subject areas

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