Umsetzungen mit Monohydrazonen von Dicarbonylverbindungen, IV. Neue Synthesen von Pyrrolen und Pyrrolinen

Synthesis of 2‐formyl‐1‐aza‐dibenzo[e,h]azulenes

“…The reaction provides the expected products 6a-c in 50-57% yield after column chromatography, while reported similar preparations are characterized with slightly lower yields (21-48%), sometimes requiring indirect methods such as catalytic dehydrogenation for formation of pyrrole ring from hydrazones [10]. NMR spectra of compounds 6a-c are characterized by multiplets at around 6.5 ppm and 7.1 ppm for the pyrrole ring protons and with broad singlet at 11.6 ppm corresponding to the proton attached to nitrogen atom.…”

“…Firstly, activated -methylene group of starting tricyclic ketones 4a-c [8,9], was reacted with (dimethylhydrazono)-acetaldehyde, prepared by reaction of glyoxal with N,N-dimethylhydrazine [10], providing hydrazonoethylidene derivatives 5a-c. Compounds 5a-c were obtained as mixtures of double-bond isomers.…”

“…Column chromatography was performed on silica gel 60 (Merck, 0.063-0.200 nm). Compounds 4a-c and (dimethylhydrazono)-acetaldehyde were synthesized as described before [8][9][10]. General Procedure for the Reaction of Ketones 4a-c with (Dimethyl-hydrazono)-acetaldehyde.…”

Dibenzo[b,f]oxepin‐10(11H)‐one and dibenzo[b,f]thiepin‐10(11H)‐one as useful synthons in the synthesis of various dibenzo[e,h]azulenes

“…Several strategies for the synthesis of 2,3‐diarylpyrroles, applicable for the annulation of pyrrole ring and preparation of tetracyclic system V , are described in the literature [31–33]. However, an original approach to the synthesis of 1‐aza‐dibenzo[ e,h ]azulenes, according to the Scheme 6, has been recently reported [14, 34].…”

Chemistry of carbofunctionally substituted hydrazones

“…As functionally substituted aldehydes are generally difficult to obtain and store this route however has only relatively limited application for the synthesis of monofunctionally substituted hydrazone [5][6][7][8][9][10][11] Condensing glyoxal 5a and substituted glyoxal 5b,c with substituted hydrazines leads to formation of mono or bis hydrazones 6 or 7 depending on molar ratio and applied reaction …”