Preparation and Catalytic Hydrogenation of Spiro[acenaphthylene‐dioxazoles] and spiro[acenaphthylene‐isoxazoles]

Wittig monoolefination of acenaphthylene‐1,2‐quinone ( 1 ) with ethyl (triphenylphosphoranylidene)acetate yields the o ‐quinomethane derivative 2 which by 1,3‐dipolar cycloaddition reactions with aromatic nitrile oxides affords regioselectively the spiro[acenaphthylene‐isoxazoles] 3 and 4 . Reaction between 1 and benzonitrile oxide gives the spiro[acenaphthylene‐dioxazole] 5 which by treatment with ethyl (triphenylphosphoranylidene)acetate gives compound 6 . Reaction between 6 and benzonitrile oxide gives regioselectively the diastereomeric dispiro compounds 7 and 7 ′. Catalytic hydrogenation of the spiro compounds 6, 7 , and 7 ′ over 10% Pd/C results in the cleavage of the dioxazole ring while cleavage of the isoxazole ring of compound 3 is achieved either by reduction over Raney nickel or by treatment with sodium ethoxide. Reduction of products prepared according Scheme 1 affords the acenaphthylene derivatives 8, 9 , and 12 – 15 .