Aspects of the chemistry of 8-azabicyclo[3.2.1]octanes

Mesylation and elimination from dimethyl 3-hydroxy-8-azabicyclo3.2.1]octane-2,8-dicarboxylate gave a conjugated alkenyl ester. Reduction of the mesyloxy ester by di-isobutylaluminium hydride was also accompanied by elimination giving an unsaturated aldehyde. Treatment of the mesylate of the corresponding monoprotected diol with potassium tert-butoxide gave a 2-unsubstituted alkene via a Grob fragmentation but a different alkene was obtained using 1,8-diazabicyclo5.4.0]undec-7-ene (DBU) in acetonitrile. Epoxidation of both the protected hydroxy-alkene and the free hydroxy-alkene was stereoselective in favour of epoxidation from the exo-face, and ring-opening of the hydroxy-epoxide using hydrogen bromide gave the diaxial bromohydrin. Treatment of a 2-iodomethyl-3-oxo-8-azabicyclo3.2.1]octane with tert-butyllithium gave a cyclopropane, whereas the corresponding iodo-alcohol gave the 1-azatricyclo5.3.0.0^4,10]decan-2-one as the major product.