Rearrangements of tetrahydroimidazo[1,5-b]isoxazole-2,3-dicarboxylates to pyrrolo[1,2-e]imidazol-6-ols, precursors of 2,5-dihydro-1H-pyrrole derivatives

Coskun N., Cetin M.

TETRAHEDRON, cilt.65, sa.3, ss.648-658, 2009 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 65 Sayı: 3
  • Basım Tarihi: 2009
  • Doi Numarası: 10.1016/j.tet.2008.11.019
  • Dergi Adı: TETRAHEDRON
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.648-658
  • Bursa Uludağ Üniversitesi Adresli: Evet

Özet

Isoxazolines 2 from the cycloaddition of imidazoline 3-oxides 1 with DMAD rearrange in the presence of methoxide to give cis-3-methoxy-7-(methoxycarbonyl)-2,7a-diaryl-5-oxo-2,3,5,7a-tetrahydro-1H-pyrrolo[1,2-e]imidazol-6-olates 3 with 100% de. The acidic hydrolysis of 3 led to kinetically controlled formation of methyl 1-forimyl-4-hydroxy-5-oxo-2-phenyl-2-((arylamino)methyl)-2,5-dihydro-1H-pyrrole-3-carboxylates 6a-e. The intramolecular transformylations of the latter to the Corresponding (E)- and (Z)-methyl 4-hydroxy-2-((N-(aryl)formamido)methyl)-5-oxo-2-phenyl-2,5-dihydro-1H-pyrrole-3-carboxylates 7a-e were shown to be substituent dependent (correlate with sigma) and characterized by Hammett type equations. The effect of temperature was investigated and the rho constants determined for the same reaction series at 50, 60 and 70 degrees C. The amide diastereomeric ratio [(E)-7]/[(Z)-7] is substituent dependent and can be described by the equation log[(E)]/[(Z)](x)=-rho sigma(1)+log[(E)]/[(Z)](x=H). (c) 2008 Elsevier Ltd. All rights reserved.