Bulletin of the Chemical Society of Japan · 1975 · 10 citations · 0 references
Natural SciencesChemistryMedicinal ChemistryNatural Product BiosynthesisOrganic ChemistrySynthetic Medicinal ChemistryHeterocycle SynthesisHeterocyclic ChemistryOrganic SynthesisIndole ChemistryIndole DerivativesIndole Synthesis
Abstract The application of Fischer’s indole synthesis to cyclohexanone 2-troponylhydrazone gave 1,2,3,4-tetrahydroindolo[2,3-b]tropone (II), which was then dehydrogenated to indolo[2,3-b]tropone (III). 8-, 10-Isopropyl-, and 7-bromoindolo[2,3-b]tropone (XIIa–c) were also obtained by a similar method. The treatment of 2-troponylhydrazones of cycloheptanone and N-benzylpiperidone with dilute sulfuric acid or PPA gave 2,3-pentamethylenepyrrolo[2,3-b]tropone (XIII) and 2-benzyl-1,2,3,4-tetrahydrocyclohept[b]pyrido[3,4-d]pyrrol-6(5H)-one (XIV) respectively. The reaction of III with phosphoryl chloride or thionyl chloride yielded 8-chlorobenzo[b]-1-azaazulene (XV), which was subsequently converted into a hydrazino derivative (XVI). The oxidative decomposition of XVI with copper sulfate in acetic acid afforded benzo[b]-1-azaazulene (XVII).