摘要:
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 good yields of the substitution product (10) isolated as the oxide 12 (69% yield) and 3% yield of the reduction product 3,3-dimethylbicyclo[2.2.2]octan-2-one (11). This photostimulated reaction is inhibited by p-dinitrobenzene and 2,2,6,6-tetramethyl-1-piperidinyloxy. In competition experiments 5 is more reactive (greater-than-or-equal-to 700) than 1-chloroadamantane (3a) and only slightly less reactive than 1-bromoadamantane (3b) (0.40) toward diphenyl phosphide ions. On the other hand, 1-chloro-3,3-dimethylbicyclo[2.2.2]octane (6) was completely unreactive toward 4 under irradiation. We suggest that the bridgehead chloride 5 reacts by the S(RN)1 mechanism of nucleophilic substitution and that the 2-oxo substituent increases the reactivity of the chloride due to the LUMO of the carbonyl group.