Fluorenone → Perhydrofluorene

Participants

Reaction Steps

A sample of 0.5 g (2.8 mmol) 9-fluorenone (Aldrich, 98%), 0.15 g Au—Pd/SiO2/TiO2 catalyst and 5 ml tetrahydrofuran (Fisher, HPLC Grade) were placed in a 20 cc stirred tank reactor and the reactor was sealed. The reactor was connected to a manifold containing a vacuum source, high-pressure hydrogen source, and a high-pressure ballast. After evacuation of residual air from the manifold lines, hydrogen was purged through the reactor to displace the air from the reactor headspace. The mixture was hydrogenated at 110 psia H2 pressure and 70° C. for 16 hours. After cooling the reactor and venting the reactor to atmospheric pressure, the contents of the reactor were filtered to remove the catalyst. GC-MS analysis of the product showed complete conversion of 9-fluorenone to two products: fluorene (53.5%) and hexahydrofluorene (46.5%). To this solution of fluorene and hexahydrofluorene was added 0.15 g of a ruthenium supported on alumina catalyst (Engelhard, 5% Ru) and the slurry was returned to the reactor. The mixture was hydrogenated at 1000 psia H2 pressure and 190° C. for 4 hours. After cooling and venting the reactor to atmospheric conditions, the catalyst was removed by filtration. GC-MS analysis of the product solution showed >99% conversion and >99% selectivity to perhydrofluorene. The cis,cis isomer of perhydrofluorene was obtained with 96% selectivity based on the GC retention time vs. commercial perhydrofluorene (Aldrich, 97%). INADEQUATE 13C NMR of the commercial perhydrofluorene confirmed the cis-cis stereochemistry of the four methine carbons in the central ring: 22.1 ppm (s), 24.3 ppm (s), 24.4 ppm (s), 29.2 ppm (s), 35.3 ppm (s), 37.3 ppm (s), 43 ppm (s), confirmed the cis-cis stereochemistry of the four methine protons in the central ring as reported by R. Meusinger in J. Prakt. Chem. 339, 128 (1997).

Provenance & Evidence