Lanthanide-Catalyst-Mediated Tandem Double Intramolecular Hydroalkoxylation/Cyclization of Dialkynyl Dialcohols

Scope and Mechanism

Sungyong Seo, Tobin J Marks

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Lanthanide-organic complexes of the general type [Ln{N-(SiMe 3)2}3] (Ln = La, Sm, Y, Lu) serve as effective precatalysts for the rapid, exo-selective, and highly regioselective tandem double intramolecular hydroalkoxylation/cyclization of primary and secondary dialkynyl dialcohols to yield the corresponding bi-exocyclic enol ethers. Conversions are highly selective with products distinctly different from those generally produced by conventional transition metal or other catalysts, and the turnover frequencies with some substrates are too large to determine accurately. The rates of terminal alkynl alcohol hydroalkoxylation/cyclization are significantly more rapid than those of internal alkynyl alcohols, arguing that steric demands dominate the cyclization transition state. The hydroalkoxylation/cyclizations of internal dialkynyl dialcohols afford excellent E selectivity. The rate law for dialkynyl dialcohol hydroalkoxylation/ cyclization is first-order in [catalyst] and zero-order in [alkynyl alcohol], as is observed for the organolanthanide-catalyzed hydroamination/cyclization of aminoalkenes, aminoalkynes, and aminoallenes, and the intramolecular single-step hydroalkoxylation/cyclization of alkynyl alcohols. An ROH/ROD kinetic isotope effect of 0.82(0.02) is observed for the tandem double hydroalkoxylation/ cyclization. These mechanistic data implicate turnover-limiting insertion of C-C unsaturation into the Ln-O bond, involving a highly organized transition state, with subsequent, rapid Ln-C protonolysis.

Original languageEnglish
Pages (from-to)5148-5162
Number of pages15
JournalChemistry - A European Journal
Volume16
Issue number17
DOIs
Publication statusPublished - May 3 2010

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Lanthanoid Series Elements
Cyclization
Rare earth elements
Catalysts
Alcohols
Ethers
Isotopes
Transition metals
Kinetics
Substrates

Keywords

  • Heterogeneous catalysis
  • Hydroalkoxylation
  • Lanthanides
  • Oxygen heterocycles
  • Parallel reactions

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Lanthanide-Catalyst-Mediated Tandem Double Intramolecular Hydroalkoxylation/Cyclization of Dialkynyl Dialcohols: Scope and Mechanism",
abstract = "Lanthanide-organic complexes of the general type [Ln{N-(SiMe 3)2}3] (Ln = La, Sm, Y, Lu) serve as effective precatalysts for the rapid, exo-selective, and highly regioselective tandem double intramolecular hydroalkoxylation/cyclization of primary and secondary dialkynyl dialcohols to yield the corresponding bi-exocyclic enol ethers. Conversions are highly selective with products distinctly different from those generally produced by conventional transition metal or other catalysts, and the turnover frequencies with some substrates are too large to determine accurately. The rates of terminal alkynl alcohol hydroalkoxylation/cyclization are significantly more rapid than those of internal alkynyl alcohols, arguing that steric demands dominate the cyclization transition state. The hydroalkoxylation/cyclizations of internal dialkynyl dialcohols afford excellent E selectivity. The rate law for dialkynyl dialcohol hydroalkoxylation/ cyclization is first-order in [catalyst] and zero-order in [alkynyl alcohol], as is observed for the organolanthanide-catalyzed hydroamination/cyclization of aminoalkenes, aminoalkynes, and aminoallenes, and the intramolecular single-step hydroalkoxylation/cyclization of alkynyl alcohols. An ROH/ROD kinetic isotope effect of 0.82(0.02) is observed for the tandem double hydroalkoxylation/ cyclization. These mechanistic data implicate turnover-limiting insertion of C-C unsaturation into the Ln-O bond, involving a highly organized transition state, with subsequent, rapid Ln-C protonolysis.",
keywords = "Heterogeneous catalysis, Hydroalkoxylation, Lanthanides, Oxygen heterocycles, Parallel reactions",
author = "Sungyong Seo and Marks, {Tobin J}",
year = "2010",
month = "5",
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T1 - Lanthanide-Catalyst-Mediated Tandem Double Intramolecular Hydroalkoxylation/Cyclization of Dialkynyl Dialcohols

T2 - Scope and Mechanism

AU - Seo, Sungyong

AU - Marks, Tobin J

PY - 2010/5/3

Y1 - 2010/5/3

N2 - Lanthanide-organic complexes of the general type [Ln{N-(SiMe 3)2}3] (Ln = La, Sm, Y, Lu) serve as effective precatalysts for the rapid, exo-selective, and highly regioselective tandem double intramolecular hydroalkoxylation/cyclization of primary and secondary dialkynyl dialcohols to yield the corresponding bi-exocyclic enol ethers. Conversions are highly selective with products distinctly different from those generally produced by conventional transition metal or other catalysts, and the turnover frequencies with some substrates are too large to determine accurately. The rates of terminal alkynl alcohol hydroalkoxylation/cyclization are significantly more rapid than those of internal alkynyl alcohols, arguing that steric demands dominate the cyclization transition state. The hydroalkoxylation/cyclizations of internal dialkynyl dialcohols afford excellent E selectivity. The rate law for dialkynyl dialcohol hydroalkoxylation/ cyclization is first-order in [catalyst] and zero-order in [alkynyl alcohol], as is observed for the organolanthanide-catalyzed hydroamination/cyclization of aminoalkenes, aminoalkynes, and aminoallenes, and the intramolecular single-step hydroalkoxylation/cyclization of alkynyl alcohols. An ROH/ROD kinetic isotope effect of 0.82(0.02) is observed for the tandem double hydroalkoxylation/ cyclization. These mechanistic data implicate turnover-limiting insertion of C-C unsaturation into the Ln-O bond, involving a highly organized transition state, with subsequent, rapid Ln-C protonolysis.

AB - Lanthanide-organic complexes of the general type [Ln{N-(SiMe 3)2}3] (Ln = La, Sm, Y, Lu) serve as effective precatalysts for the rapid, exo-selective, and highly regioselective tandem double intramolecular hydroalkoxylation/cyclization of primary and secondary dialkynyl dialcohols to yield the corresponding bi-exocyclic enol ethers. Conversions are highly selective with products distinctly different from those generally produced by conventional transition metal or other catalysts, and the turnover frequencies with some substrates are too large to determine accurately. The rates of terminal alkynl alcohol hydroalkoxylation/cyclization are significantly more rapid than those of internal alkynyl alcohols, arguing that steric demands dominate the cyclization transition state. The hydroalkoxylation/cyclizations of internal dialkynyl dialcohols afford excellent E selectivity. The rate law for dialkynyl dialcohol hydroalkoxylation/ cyclization is first-order in [catalyst] and zero-order in [alkynyl alcohol], as is observed for the organolanthanide-catalyzed hydroamination/cyclization of aminoalkenes, aminoalkynes, and aminoallenes, and the intramolecular single-step hydroalkoxylation/cyclization of alkynyl alcohols. An ROH/ROD kinetic isotope effect of 0.82(0.02) is observed for the tandem double hydroalkoxylation/ cyclization. These mechanistic data implicate turnover-limiting insertion of C-C unsaturation into the Ln-O bond, involving a highly organized transition state, with subsequent, rapid Ln-C protonolysis.

KW - Heterogeneous catalysis

KW - Hydroalkoxylation

KW - Lanthanides

KW - Oxygen heterocycles

KW - Parallel reactions

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