exo-Selective inverse-electron-demand hetero Diels-Alder reactions of norbornene with 5-benzylidine-2-arylimino-3-aryl-thiazolidine-4-thiones at room temperature

Erol Ş., Dogan I.

TETRAHEDRON, vol.69, no.4, pp.1337-1344, 2013 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 69 Issue: 4
  • Publication Date: 2013
  • Doi Number: 10.1016/j.tet.2012.11.085
  • Journal Name: TETRAHEDRON
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Index Chemicus (IC)
  • Page Numbers: pp.1337-1344
  • Keywords: Inverse-electron-demand hetero, Diels-Alder reaction, exo-Selectivity, Thiadiene, Norbornene, Bioconjugation, Atroposelectivity, BICYCLIC OLEFINS, STEREOSELECTIVITY, ADDITIONS, 7,7-DIMETHYLNORBORNENE, STEREOCHEMISTRY, CYCLOADDITIONS, BIOCONJUGATION, DERIVATIVES
  • Istanbul University-Cerrahpasa Affiliated: No

Abstract

2-Arylimino-3-aryl-thiazolidine-4-thiones were synthesized from the corresponding thiazolidine-4-ones using Lawesson's reagent (LR) and converted into 5-benzylidine-2-arylimino-3-aryl-thiazolidine-4-thiones by reaction with benzaldehyde, which were then used as heterodienes in the inverse-electron-demand hetero Diels-Alder cycloadditions with norbornene as a dienophile at 25 degrees C. The reactions with norbornene were found to proceed with 100% exo-selectivity as determined by NMR experiments. The hetero Diels-Alder reactions with axially chiral heterodienes with Delta G(#)> 116 kJ/mol showed kinetic atroposelectivities up to 11:1. However, the products were found to equilibrate, as revealed by the 97.1 kJ/mol barrier to hindered rotation of the most sterically hindered product, to produce 2:1 diastereoselectivities after the 24 h reaction time. (c) 2012 Elsevier Ltd. All rights reserved.