Synthesis of stable azomethineylides by the rearrangement of 1,3-dipolar cycloadducts of 3,4-dihydroisoquinoline-2-oxides with DMAD

Coskun N., Tuncman S.

TETRAHEDRON, vol.62, no.7, pp.1345-1350, 2006 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 62 Issue: 7
  • Publication Date: 2006
  • Doi Number: 10.1016/j.tet.2005.11.040
  • Journal Name: TETRAHEDRON
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1345-1350
  • Keywords: isoquinoline, 1-aryl-1-1,2,3,4-tetrahydroisoquinoline, THI, Pictet-Spengler, oxidation with H2O2-tungstate, 3,4-dihydroisoquinoline2-oxide, rearrangement, isoxazoloisoquinoline, stable azomethine ylide, 4-isoxazoline rearrangement mechanism, alkyne, DMAD, dipolar cycloaddition, synthesis, heterocycles, RING-OPENING REACTIONS, IMIDAZOLINE 3-OXIDES, DIASTEREOSELECTIVE ADDITION, CYCLOADDITION REACTIONS, ORGANIC-SYNTHESIS, ARYL ISOCYANATES, N-OXIDES, REGIO, NITRONES
  • Bursa Uludag University Affiliated: Yes


1-Aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines were prepared according to a one-pot procedure involving the reaction of 2-(3,4-dimethoxyl)-ethylamine with aromatic aldehydes in TFA at reflux. The tetrahydroisoquinolines were treated with H2O2-WO42- in methanol at room temperature to give the corresponding 3,4-dihydroisoquinoline-2-oxides. Treatment of these cyclic nitrones with DMAD in toluene at room temperature gave the corresponding isoxazolo[3,2-a]isoquinolines. These compounds were heated in toluene at reflux to give the corresponding ylides in high yields (Method A). The effect of the substituents on the rate of the rearrangement of such compounds prompted us to discuss a new mechanism involving consecutive C-C bond heterolysis and 1,3-sigmatropic shift. A one-pot reaction involving the treatment of the nitrones with equimolar amounts of DMAD in refluxing toluene also gave the ylides (Method B). The structures of the prepared compound,, were elucidated by spectral means and elemental analyses. (c) 2005 Elsevier Ltd. All rights reserved.