Synthesis of Enantiopure 1-Azabicyclo[3.2.2]nonanes via Stereoselective Capture of Chiral Carbocations

A new class of doubly functionalized and enantiomerically pure 1-azabicyclo[3.2.2]nonanes derived from quincorine and quincoridine is described. 2,5-Disubstituted quinuclidines with a C9-mesyloxy group were easily transformed into the corresponding halides upon treatment with lithium salts. Subsequent silver salt-mediated ring expansion stereoselectively furnished the title azabicyclics. Chiral carbocations which are configurationally stable and nonplanar are postulated to account for the striking stereoselectivity of the capture of external nucleophile. 5-Ethynyl-2-iodomethylquinuclidines afford the α-benzoyloxy amines rather than α-methoxy amines, even in MeOH.