The Reactivity of 1-Chloro-3,3-dimethylbicyclooctan-2-one in the Radical Mechanism of Nucleophilic Substitution

Article abstract of DOI:10.1021/jo00004a044

1-Chloro-3,3-dimethylbicyclo<2.2.2>octan-2-one (5) does not react with diphenyl phosphide ions (4) in liquid ammonia in the dark in 240 min, but under irradiation (30 min) it gives good yields of the substitution product (10) isolated as the oxide 12 (69percent yield) and 3percent yield of the reduction product 3,3-dimethylbicyclo<2.2.2>octan-2-one (11).The photostimulated reaction is inhibited by p-dinitrobenzene and 2,2,6,6-tetramethyl-1-piperidinyloxyl.In competition experiments 5 is more reactive (>/= 700) than 1-chloroadamantane (3a) and only slightly less reactive than 1-bromoadama ntane (3b) (0.40) toward diphenyl phosphide ions.On the other hand, 1-chloro-3,3-dimethylbicyclo<2.2.2>octane (6) was completely unreactive towards 4 under irradiation.We suggest that the bridgehead chloride 5 reacts by the S_RN1 mechanism of nucleophilic substitution and that the 2-oxo substitution increases the reactivity of the chloride due to the LUMO of the carbonyl group.