Light Induced Reductive Ring Contractions of Sixmembered Cyclic Iminium Ions

József Nagy, Zoltán Madarász, Rudolf Rapp, Áron Szöllösy, József Nyitrai, Dietrich Döpp

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14 Citations (Scopus)

Abstract

Photochemically induced reductive ring contractions, previously observed for 2,5-dihydro-1,2,4-triazines, have also been verified for 1,4-dihydropyrimidines 2a,b, the dihydro-1,2,4,5-tetrazine 9, and dihydro-1,3,5-triazines 11a,b giving rise to fivemembered fully unsaturated heterocycles (pyrroles 4a,b, imidazoles 13a,b, and triazole 10, respectively). The 1,4-dihydropyrazines 15a-j tend to decompose in acidified 2-propanol in the dark, but on irradiation they also undergo reductive ring contraction furnishing solely the 1,2,5-triarylpyrroles 16a-d rather than the (a priori also possible) isomeric 1,3,4-triarylpyrroles 17a-d. In contrast, the 3,6-diphenylpyrid-azine 18 gives the 4-isopropyl-analogue 19 in low yield upon irradiation in hydrogen chloride saturated 2-propanol.

Original languageEnglish
Pages (from-to)281-290
Number of pages10
JournalAdvanced Synthesis and Catalysis
Volume342
Issue number3
Publication statusPublished - Dec 1 2000

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Keywords

  • Dihydroaromatic azines
  • Electron transfer
  • Heterocycles
  • Photochemistry
  • Ring contractions

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

Cite this

Nagy, J., Madarász, Z., Rapp, R., Szöllösy, Á., Nyitrai, J., & Döpp, D. (2000). Light Induced Reductive Ring Contractions of Sixmembered Cyclic Iminium Ions. Advanced Synthesis and Catalysis, 342(3), 281-290.