Stoichiometric reactions of enamines derived from diphenylprolinol silyl ethers with nitro olefins and lessons for the corresponding organocatalytic conversions - A survey

Dieter Seebach, Xiaoyu Sun, Marc Olivier Ebert, W. Bernd Schweizer, Nirupam Purkayastha, Albert K. Beck, Jörg Duschmalé, Helma Wennemers, Takasuke Mukaiyama, Meryem Benohoud, Yujiro Hayashi, Markus Reiher

Research output: Contribution to journalArticlepeer-review

59 Citations (Scopus)

Abstract

The stoichiometric reactions of enamines prepared from aldehydes and diphenyl-prolinol silyl ethers (intermediates of numerous organocatalytic processes) with nitro olefins have been investigated. As reported in the last century for simple achiral and chiral enamines, the products are cyclobutanes (4 with monosubstituted nitro-ethenes), dihydro-oxazine N-oxide derivatives (5 with disubstituted nitro-ethenes), and nitro enamines derived from γ-nitro aldehydes (6, often formed after longer reaction times). The same types of products were shown to be formed, when the reactions were carried out with peptides H-Pro-Pro-Xaa-OMe that lack an acidic H-atom. Functionalized components such as alkoxy enamines, nitro-acrylates, acetamido-nitro-ethylene, or hydroxylated nitro olefins also form products carrying the diphenyl-prolinol silyl ether as a substituent. All of these products must be considered intermediates in the corresponding catalytic reactions; the investigation of their chemical properties provided useful hints about the rates, the conditions, the catalyst resting states or irreversible traps, and/or the limitations of the corresponding organocatalytic processes. High-level DFT and MP2 computations of the structures of alkoxy enamines and thermodynamic data of a cyclobutane dissociation are also described. Some results obtained with the stoichiometrically prepared intermediates are not compatible with previous mechanistic proposals and assumptions.

Original languageEnglish
Pages (from-to)799-852
Number of pages54
JournalHelvetica Chimica Acta
Volume96
Issue number5
DOIs
Publication statusPublished - 2013 May
Externally publishedYes

Keywords

  • Aldehydes
  • Catalysis
  • Cyclobutanes
  • Density-functional theory (DFT)
  • Nitro olefins
  • Oseltamivir
  • Oxazine N-oxides

ASJC Scopus subject areas

  • Catalysis
  • Biochemistry
  • Drug Discovery
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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