Reduction of 7-Methylenebicyclo[3.3.1]nonan-3-one and Related Compounds: Structural Investigation of the Products

Abstract

Abstract Hydrogenation of 7-methylenebicyclo[3.3.1]nonan-3-one (1) over platinum oxide in acetic acid yielded 7α-methylbicyclo[3.3.1]nonan-3α-ol (2) as the sole product. Hydrogenation of (1) in ethyl acetate afforded 7α-methylbicyclo[3.3.1]nonan-3-one (3) as a reduced product and 7-methylbicyclo[3.3.1]non-6-en-3-one (4) as an isomerized product. Hydrogenation of 1 over palladium on carbon gave no reduced product but 4 in 100% conversion. Hydrogenation of 7-methylenebicyclo[3.3.1]nonan-3α-ol (7) and -3β-ol (8) over platinum oxide in acetic acid gave 2 and 7α-methylbicyclo[3.3.1]nonan-3β-ol (5), respectively. From studies based on NMR spectroscopy with use of a shift-reagent, it is concluded that the major conformer of 2 and 5 is of chair-boat form. By the equilibration experiment between 2 and 5 using aluminum isopropoxide in isopropyl alcohol at 110°C, the ΔG° value was found to be −2.2 kcal/mol.