Oxidative Cyclisierung von Anilinopyrazolen zu Pyrazolo[1,5‐a]benzimidazolen

Abstract

Free Radical Reactions of N-Heterocyclic Compounds, XIVI1l. -Oxidative Cyclization of Anilinopyrazoles to Pyrazolo[ 1,5-a]benzimidazoles* Substituted Anilinopyrazoles 1 were oxidized by dibenzoyl undergo cyclization reaction with formation of pyrazolo[ 1 5 peroxide or lead(1V) oxide. Different oxidation products were a]benzimidazoles 4. The structures of compounds 4 were proisolated depending on the substituents in the anilino group of ven by 'H-and I3C-NMR spectroscopy, I5N labeling and anilinopyrazoles 1. Intermediate pyrazolyl radicals 5, which transformation of 4e to the betain 7e. could be trapped by triphenylmethyl or phenoxyl radicals,

Highly Efficient Dehydrogenation of 5‐Benzyl‐3‐phenyl‐2‐thioxoimidazolidin‐4‐one: Microwave versus Flash Vacuum Pyrolysis Conditions

“…However, acceptable yields of 4 could be obtained without significant formation of secondary or carbonaceous products at 450°C. [15] To address the origin of compounds 7 and 8, FVP reactions of 4 at 450°C were performed. [13] Imidazoindolone 8 can be formed by intramolecular cyclization of thioxoimidazolidinone 4 involving an additional dehydrogenation reaction.…”

Approaches towards the synthesis of 5-aminopyrazoles

“…The synthesis of a few 3-substituted 5-amino-4-cyanopyrazoles 84 has recently been reported by the treatment of 1,1-dicyano-2-methoxy-3-substituted propenes 83 with hydrazine hydrate in ethanolic TEA ( Scheme 23 ) [ 64 – 65 ].…”