(-)-Sparteine Mediated Alpha-Deprotonation Of Quinuclidine N-Oxide

Addition of RLi to a mixture of quinuclidine N-oxide ( 1) and (-)- sparteine in toluene at - 78degrees, followed by quenching with benzaldehyde gives threo ( 3, 34% ee) and erythro ( 4, 40% ee) adducts with moderate enantioselectivity. Reaction of RLi with 1 followed by treatment with (-)- sparteine prior to electrophile addition affords racemic products while no deprotonation is observed when 1 is treated with a preformed complex of RLi and (-)- sparteine. These results indicate that only a sequential association of 1 with RLi and (-)- sparteine leads to the complex undergoing enantioselective deprotonation.