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Kinetics and Mechanism of Allene Racemization Catalyzed by a Gold N-Heterocyclic Carbene Complex

Publication ,  Journal Article
Li, H; Harris, RJ; Nakafuku, K; Widenhoefer, RA
Published in: Organometallics
July 11, 2016

The kinetics of the racemization of 1,3-disubstituted allenes catalyzed by (IPr)AuOTf (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidine) has been investigated. The rate of gold-catalyzed allene racemization obeyed the following second-order rate law: rate = krac[allene][Au]. An analysis of the rate of the gold-catalyzed racemization of 1-aryl-1,2-butadienes as a function of allene electron donor ability established moderate depletion of electron density on the C1 allenyl carbon atom in the rate-limiting transition state for racemization. Analysis of the temperature dependence of the rate of racemization of 1-(p-tolyl)-1,2-butadiene established the activation parameters ΔH∞ = 8.3 ± 1 kcal mol-1 and ΔS∞ = -28 ± 4 eu. These observations were in accord with a mechanism for allene racemization involving turnover-limiting, intermolecular allene exchange followed by rapid allene stereomutation.

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Published In

Organometallics

DOI

EISSN

1520-6041

ISSN

0276-7333

Publication Date

July 11, 2016

Volume

35

Issue

13

Start / End Page

2242 / 2248

Related Subject Headings

  • Organic Chemistry
  • 3406 Physical chemistry
  • 3402 Inorganic chemistry
  • 0399 Other Chemical Sciences
  • 0305 Organic Chemistry
  • 0302 Inorganic Chemistry
 

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Li, H., Harris, R. J., Nakafuku, K., & Widenhoefer, R. A. (2016). Kinetics and Mechanism of Allene Racemization Catalyzed by a Gold N-Heterocyclic Carbene Complex. Organometallics, 35(13), 2242–2248. https://doi.org/10.1021/acs.organomet.6b00307
Li, H., R. J. Harris, K. Nakafuku, and R. A. Widenhoefer. “Kinetics and Mechanism of Allene Racemization Catalyzed by a Gold N-Heterocyclic Carbene Complex.” Organometallics 35, no. 13 (July 11, 2016): 2242–48. https://doi.org/10.1021/acs.organomet.6b00307.
Li H, Harris RJ, Nakafuku K, Widenhoefer RA. Kinetics and Mechanism of Allene Racemization Catalyzed by a Gold N-Heterocyclic Carbene Complex. Organometallics. 2016 Jul 11;35(13):2242–8.
Li, H., et al. “Kinetics and Mechanism of Allene Racemization Catalyzed by a Gold N-Heterocyclic Carbene Complex.” Organometallics, vol. 35, no. 13, July 2016, pp. 2242–48. Scopus, doi:10.1021/acs.organomet.6b00307.
Li H, Harris RJ, Nakafuku K, Widenhoefer RA. Kinetics and Mechanism of Allene Racemization Catalyzed by a Gold N-Heterocyclic Carbene Complex. Organometallics. 2016 Jul 11;35(13):2242–2248.
Journal cover image

Published In

Organometallics

DOI

EISSN

1520-6041

ISSN

0276-7333

Publication Date

July 11, 2016

Volume

35

Issue

13

Start / End Page

2242 / 2248

Related Subject Headings

  • Organic Chemistry
  • 3406 Physical chemistry
  • 3402 Inorganic chemistry
  • 0399 Other Chemical Sciences
  • 0305 Organic Chemistry
  • 0302 Inorganic Chemistry