Synthesis of 1-azabicyclic systems by double cyclization

5-Cyano-1-azabicyclo[3.3.0]octane (1) was prepared in one step from 1,7-dichloro-4-heptanone (4) under mild conditions. The application of this method for the preparation of 5-cyano-4,6-dimethyl-1-azabicy-clo[3.3.0]octane (11) gave two diastereomers in equilibrium. The NMR measurements of 11 and its reduced compound 15 showed that the major isomer is the cis-exo form, and the minor isomer is the trans form. Molecular orbital calculations indicated that the cis-exo form is more stable than the trans form, in agreement with the experimental results. Furthermore, 6-cyano-1-azabicyclo[4.3.0]nonane (17) and 1-azabicy-clo[4.4.0]decane (19), both including a six-membered ring, were prepared from appropriate haloketones by using this double cyclization method.