Catalytic hydrogenation with frustrated lewis pairs: Selectivity achieved by size-exclusion design of lewis acids

Gábor Erös, Krisztina Nagy, Hasan Mehdi, Imre Pápai, Péter Nagy, Péter Király, Gábor Tárkányi, Tibor Soõs

Research output: Contribution to journalArticle

94 Citations (Scopus)

Abstract

Catalytic hydrogenation that utilizes frustrated Lewis pair (FLP) catalysts is a subject of growing interest because such catalysts offer a unique opportunity for the development of transition-metal-free hydrogenations. The aim of our recent efforts is to further increase the functional-group tolerance and chemoselectivity of FLP catalysts by means of size-exclusion catalyst design. Given that hydrogen molecule is the smallest molecule, our modified Lewis acids feature a highly shielded boron center that still allows the cleavage of the hydrogen but avoids undesirable FLP reactivity by simple physical constraint. As a result, greater latitude in substrate scope can be achieved, as exemplified by the chemoselective reduction of α,β-unsaturated imines, ketones, and quinolines. In addition to synthetic aspects, detailed NMR spectroscopic, DFT, and 2H isotopic labeling studies were performed to gain further mechanistic insight into FLP hydrogenation.

Original languageEnglish
Pages (from-to)574-585
Number of pages12
JournalChemistry - A European Journal
Volume18
Issue number2
DOIs
Publication statusPublished - Jan 9 2012

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Lewis Acids
Hydrogenation
Catalysts
Acids
Hydrogen
Quinolines
Molecules
Boron
Imines
Ketones
Discrete Fourier transforms
Labeling
Functional groups
Transition metals
Nuclear magnetic resonance
Substrates

Keywords

  • chemoselectivity
  • hydrogenation
  • Lewis acids
  • Lewis bases
  • size exclusion

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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abstract = "Catalytic hydrogenation that utilizes frustrated Lewis pair (FLP) catalysts is a subject of growing interest because such catalysts offer a unique opportunity for the development of transition-metal-free hydrogenations. The aim of our recent efforts is to further increase the functional-group tolerance and chemoselectivity of FLP catalysts by means of size-exclusion catalyst design. Given that hydrogen molecule is the smallest molecule, our modified Lewis acids feature a highly shielded boron center that still allows the cleavage of the hydrogen but avoids undesirable FLP reactivity by simple physical constraint. As a result, greater latitude in substrate scope can be achieved, as exemplified by the chemoselective reduction of α,β-unsaturated imines, ketones, and quinolines. In addition to synthetic aspects, detailed NMR spectroscopic, DFT, and 2H isotopic labeling studies were performed to gain further mechanistic insight into FLP hydrogenation.",
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T2 - Selectivity achieved by size-exclusion design of lewis acids

AU - Erös, Gábor

AU - Nagy, Krisztina

AU - Mehdi, Hasan

AU - Pápai, Imre

AU - Nagy, Péter

AU - Király, Péter

AU - Tárkányi, Gábor

AU - Soõs, Tibor

PY - 2012/1/9

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N2 - Catalytic hydrogenation that utilizes frustrated Lewis pair (FLP) catalysts is a subject of growing interest because such catalysts offer a unique opportunity for the development of transition-metal-free hydrogenations. The aim of our recent efforts is to further increase the functional-group tolerance and chemoselectivity of FLP catalysts by means of size-exclusion catalyst design. Given that hydrogen molecule is the smallest molecule, our modified Lewis acids feature a highly shielded boron center that still allows the cleavage of the hydrogen but avoids undesirable FLP reactivity by simple physical constraint. As a result, greater latitude in substrate scope can be achieved, as exemplified by the chemoselective reduction of α,β-unsaturated imines, ketones, and quinolines. In addition to synthetic aspects, detailed NMR spectroscopic, DFT, and 2H isotopic labeling studies were performed to gain further mechanistic insight into FLP hydrogenation.

AB - Catalytic hydrogenation that utilizes frustrated Lewis pair (FLP) catalysts is a subject of growing interest because such catalysts offer a unique opportunity for the development of transition-metal-free hydrogenations. The aim of our recent efforts is to further increase the functional-group tolerance and chemoselectivity of FLP catalysts by means of size-exclusion catalyst design. Given that hydrogen molecule is the smallest molecule, our modified Lewis acids feature a highly shielded boron center that still allows the cleavage of the hydrogen but avoids undesirable FLP reactivity by simple physical constraint. As a result, greater latitude in substrate scope can be achieved, as exemplified by the chemoselective reduction of α,β-unsaturated imines, ketones, and quinolines. In addition to synthetic aspects, detailed NMR spectroscopic, DFT, and 2H isotopic labeling studies were performed to gain further mechanistic insight into FLP hydrogenation.

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