9-(2′,5′-Dimethyl-4′-pyridyl)fluorene in syntheses of fluorospirodihydrofuropyridine and pyridofluoranthene

1,2,5-Trimethyl-4-(9′-fluorenylidene)piperidine, which is formed by condensation of fluorene with 1,2,5-trimethyl-4-piperidone, is converted catalytically to 9(2′,5′-dimethyl-4′-pyridyl)fluorene, from which 2-methylpyrido[4,5-a]fluoranthene and its demethylated analog were obtained by catalytic dehydrocyclization. Oxidation of 9-(2′,5′-dimethy1-4′-pyridyl)fluorene gave 9-(2′,5′-dimethyl-4′-pyridyl)9-fluorenol and fluorene-9-spiro-4′-(6′-oxo-2′-carboxypyrido[4′,5′-c]-4′-6′-dihydrofuran). 6-Methyl-2-phenyl-7-(9′-fluorenyl)indolizine was synthesized by the Chichibabin method. © 1979 Plenum Publishing Corporation.