Acid-catalysed intramolecular C-alkylation in β,γ-unsaturated diazomethyl ketones. Part 5. Synthesis of functionalised hydrofluorene derivatives via novel fragmentation reactions

Abstract

Some transformations of the hexahydro-4a-hydroxy-4,9a-ethano-1H-fluoren-11 -ones (4a) and (4b), derived via acid-catalysed alkylation-rearrangement reactions, are described. While hydrogenolysis of the demethoxyhydroxycycIopentanone (4a) with lithium–ammonia proceeds with retention of configuration to give the respective bridged-ketone (6a) exclusively, the corresponding methoxy analogue (4b) on the other hand gave the respective hydrogenolysed product (6b) in a very low yield, which however, was obtained along with its C-4a epimer (5b) by catalytic hydrogenolysis in the presence of perchloric acid. Formylation–oxidation of (6a) or the alkoxy ketones (14) and (15) gave the β,γ- unsaturated acid (8a); the methoxy analogue (6b) under similar conditions gave the respective acid (8b), arising through novel fragmentation reactions. Under certain conditions, (6a) gave the cis-dicarboxylic acid (10a) along with (8a). The hydroxy ketones (4a) and (4b) underwent fragmentations with ethyl formate and sodium hydride or with perchloric acid in ethanol to give the angularly functionalised esters (18a) and (18b).