Atom-efficient carbon-oxygen bond formation processes. DFT analysis of the intramolecular hydroalkoxylation/cyclization of alkynyl alcohols mediated by lanthanide catalysts

Alessandro Motta, Ignazio L. Fragalà, Tobin J Marks

Research output: Contribution to journalArticle

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Abstract

This contribution focuses on organolanthanide-mediated hydroalkoxylation processes and investigates the hydroalkoxylation/cyclization of a prototypical alkynyl alcohol, HO(CH2)3C - CR, (R = H, CH3, TMS) catalyzed by the homoleptic La[N(SiMe3)2]3 amido complex using density functional theory. The reaction is found to occur in two steps, namely, cyclization with concerted Ln-C and C-O bond formation and subsequent Ln-C protonolysis. Calculations are carried out for: (i) insertion of the alkynyl moiety into the La-O bond via a four-center transition state and (ii) protonolysis by a second substrate molecule. The cyclized ether then dissociates, restoring the active catalyst. Analysis is also carried out on the effects of other Ln3+ ions and alkyne R substituents on the reaction energetics in comparison to the analogous organolanthanide-mediated aminoalkyne and aminoolefin hydroamination processes. DFT energetic profiles are computed for the turnover-limiting insertion of the alkynyl alcohol C - C triple bond into the La-O bond, and the geometries and stabilities of reactants, intermediates, and products are analyzed. The picture that emerges involves a concerted, rate-limiting insertion of the alkyne fragment into the La-O bond via a highly organized transition state (δH calcd = 15.3 kcal/mol, δS calcd = -6.5 cal/(mol K)). The resulting cyclopentylmethylene complex then undergoes exothermic protonolysis to regenerate the active catalyst. Thermodynamic and kinetic estimates are in excellent agreement with experimental data.

Original languageEnglish
Pages (from-to)2004-2012
Number of pages9
JournalOrganometallics
Volume29
Issue number9
DOIs
Publication statusPublished - May 10 2010

Fingerprint

Lanthanoid Series Elements
Alkynes
Cyclization
Discrete Fourier transforms
insertion
alcohols
Carbon
Alcohols
alkynes
Oxygen
catalysts
Atoms
Catalysts
carbon
oxygen
Ether
Density functional theory
atoms
Thermodynamics
Ions

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Atom-efficient carbon-oxygen bond formation processes. DFT analysis of the intramolecular hydroalkoxylation/cyclization of alkynyl alcohols mediated by lanthanide catalysts. / Motta, Alessandro; Fragalà, Ignazio L.; Marks, Tobin J.

In: Organometallics, Vol. 29, No. 9, 10.05.2010, p. 2004-2012.

Research output: Contribution to journalArticle

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abstract = "This contribution focuses on organolanthanide-mediated hydroalkoxylation processes and investigates the hydroalkoxylation/cyclization of a prototypical alkynyl alcohol, HO(CH2)3C - CR, (R = H, CH3, TMS) catalyzed by the homoleptic La[N(SiMe3)2]3 amido complex using density functional theory. The reaction is found to occur in two steps, namely, cyclization with concerted Ln-C and C-O bond formation and subsequent Ln-C protonolysis. Calculations are carried out for: (i) insertion of the alkynyl moiety into the La-O bond via a four-center transition state and (ii) protonolysis by a second substrate molecule. The cyclized ether then dissociates, restoring the active catalyst. Analysis is also carried out on the effects of other Ln3+ ions and alkyne R substituents on the reaction energetics in comparison to the analogous organolanthanide-mediated aminoalkyne and aminoolefin hydroamination processes. DFT energetic profiles are computed for the turnover-limiting insertion of the alkynyl alcohol C - C triple bond into the La-O bond, and the geometries and stabilities of reactants, intermediates, and products are analyzed. The picture that emerges involves a concerted, rate-limiting insertion of the alkyne fragment into the La-O bond via a highly organized transition state (δH† calcd = 15.3 kcal/mol, δS† calcd = -6.5 cal/(mol K)). The resulting cyclopentylmethylene complex then undergoes exothermic protonolysis to regenerate the active catalyst. Thermodynamic and kinetic estimates are in excellent agreement with experimental data.",
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AB - This contribution focuses on organolanthanide-mediated hydroalkoxylation processes and investigates the hydroalkoxylation/cyclization of a prototypical alkynyl alcohol, HO(CH2)3C - CR, (R = H, CH3, TMS) catalyzed by the homoleptic La[N(SiMe3)2]3 amido complex using density functional theory. The reaction is found to occur in two steps, namely, cyclization with concerted Ln-C and C-O bond formation and subsequent Ln-C protonolysis. Calculations are carried out for: (i) insertion of the alkynyl moiety into the La-O bond via a four-center transition state and (ii) protonolysis by a second substrate molecule. The cyclized ether then dissociates, restoring the active catalyst. Analysis is also carried out on the effects of other Ln3+ ions and alkyne R substituents on the reaction energetics in comparison to the analogous organolanthanide-mediated aminoalkyne and aminoolefin hydroamination processes. DFT energetic profiles are computed for the turnover-limiting insertion of the alkynyl alcohol C - C triple bond into the La-O bond, and the geometries and stabilities of reactants, intermediates, and products are analyzed. The picture that emerges involves a concerted, rate-limiting insertion of the alkyne fragment into the La-O bond via a highly organized transition state (δH† calcd = 15.3 kcal/mol, δS† calcd = -6.5 cal/(mol K)). The resulting cyclopentylmethylene complex then undergoes exothermic protonolysis to regenerate the active catalyst. Thermodynamic and kinetic estimates are in excellent agreement with experimental data.

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