Bulletin of the Korean Chemical Society

  • 제28권6호
  • /
  • Pages.917-920
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  • 2007
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  • 0253-2964(pISSN)
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  • 1229-5949(eISSN)
대한화학회 (Korean Chemical Society)
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Ketene-Forming Elimination Reactions from Aryl Thienylacetates Promoted by R2NH in MeCN. Effects of Base-Solvent and β-Aryl Group

  • Pyun, Sang-Yong (Department of Chemistry, Pukyong National University) ;
  • Cho, Eun-Ju (Department of Chemistry, Pukyong National University) ;
  • Seok, Hyoun-Jung (Department of Chemistry, Pukyong National University) ;
  • Kim, Ju-Chang (Department of Chemistry, Pukyong National University) ;
  • Lee, Seok-Hee (Division of Applied Chemical Engineering, Pukyong National University) ;
  • Cho, Bong-Rae (Department of Chemistry, Korea University)
  • 발행 : 2007.06.20
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초록

Ketene-forming eliminations from C4H3(S)CH2C(O)O-C6H3-2-X-4-NO2 (1) promoted by R2NH in MeCN have been studied kinetically. The reactions are second-order and exhibit Bronsted β =0.51-0.62 and |βlg|= 0.47-0.53. Hence, an E2 mechanism is evident. The Bronsted β increased from 0.33 to 0.53 and |βlg| remained nearly the same by the change of the base-solvent from Bz(i-Pr)NH/Bz(i-Pr)NH2+ in 70 mol% MeCN(aq) to Bz(i-Pr)NH-MeCN, indicating a change to a more symmetrical transition state with similar extents of Cβ -H and Cα -OAr bond cleavage. When the β-aryl group was changed from thienyl to phenyl in MeCN, the β value increased from 0.53 to 0.73 and |βlg| decreased from 0.53 to 0.43. This indicates that the transition state became skewed toward more Cβ -H bond breaking with less Cα-OAr bond cleavage. Noteworthy is the greater double bond stabilizing ability of the thienyl group in the ketene-forming transition state.

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피인용 문헌

  1. in 70 mol% MeCN(aq). Effects of β-Aryl on the Ketene-Forming Transition-State vol.35, pp.7, 2014, https://doi.org/10.5012/bkcs.2014.35.7.2143
  2. NH in MeCN: Effects of Base Solvent and β-Aryl Group on the Ketene-forming Transition State vol.38, pp.11, 2017, https://doi.org/10.1002/bkcs.11285
  3. Kinetics of elimination reactions of 1,2-diphenyl ethyl substrates in acetonitrile: A mechanistic change in the presence of a strong base vol.40, pp.8, 2008, https://doi.org/10.1002/kin.20329