Why is the reaction of ethyl (2-cyanoacetyl)carbamate with ethyl orthoformate highly stereoselective?

Kuangsen Sung, Ming Chi Lin, Pin Mei Huang, Bo Ren Zhuang, Robert Sung, Ru Rong Wu

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The reaction of ethyl (2-cyanoacetyl)carbamate (1) with ethyl orthoformate in the presence of acetic anhydride is highly stereoselective and only E-ethyl (2-cyano-3-ethoxyacryloyl)carbamate (E-2) is isolated. The reaction is thermodynamically controlled and the product distribution depends on the relative stability between E-2 and Z-2. Both the resonance stabilization of 1.47 kcal mol-1 and the steric hindrance of 2.28 kcal mol-1 in favour of E-2 contribute to the relative stability (3.75 kcal mol-1) between Z-2 and E-2, which is calculated from four isodesmic reactions, and this is the reason why the reaction of compound 1 with ethyl orthoformate is highly stereoselective. The electron-withdrawing ability of some substituents was evaluated. The sequence of π-accepting ability is C(O)NHC(O)OEt > C(O)NH2 > CN and the sequence of σ-accepting ability is CN > C(O)NHC(O)OEt > C(O)NH2.

Original languageEnglish
Pages (from-to)1183-1189
Number of pages7
JournalJournal of Physical Organic Chemistry
Volume18
Issue number12
DOIs
Publication statusPublished - 2005 Dec

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry

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