Acid-Catalyzed Intramolecular C-Alkylation in β,γ-Unsaturated Diazomethyl Ketones. 3. A Simple Synthetic Route to Hexahydro-4,9a-ethano-1H-fluoren-11-ones, Hexahydro-6H-pentalenoindan-4-ones, and Hexahydrocyclobutafluoren-2(1H)-ones

Article abstract of DOI:10.1021/jo00148a023

C-Alkylation rearrangements of the tetrahydrofluorene diazoacetyl derivatives 1a-e with tetrahydrofluoboric acid in nitromethane and toluene-p-sulfonic acid in boiling benzene are shown to give, in good to excellent yields, the hydroxycyclopentanones 3a-e and the tetrahydro-6H-pentaleno<6a,1-a>indan-4-ones 4a-e, respectively.These undergo stereospecific catalytic hydrogenation to the respective bridged cyclopentanones 14a-e and the hexahydroindan-4-ones 15a-e.The cyclization of the diazo ketones 1c-e with trifluoroacetic acid in chloroform gives the respective angularly fused unsaturated cyclobutanones 2c-e, which undergo highly stereoselective catalytic hydrogenation to the corresponding trans angularly substituted hexahydrofluorene-cyclobutanone compounds 16c-e.