Synthesis of bridged azabicyclic ketones. Solvolysis of enol ether ethylene ketal N-cholramines in acidic medium

The syntheses of 2-azabicyclo[2.2.2]octanes, 2-azabicyclo[3.2.1]octanes and 2-azabicyclo[3.3.1]nonanes, by means of intramolecular cyclizations of N-chloramines under acidic solvolytic conditions, are described. The cyclization is regioselective for the enol ethers and dioxolanes. The latter reacts in an unsaturated open form. The experimental data lead us to conclude that the reaction mechanism involves an electrophilic chlorination of the enol ether double bond.