Azabicyclononane durch Fragmentierung, II. Regiospezifische (Grob‐)Fragmentierung zur Darstellung von 3‐Azabicyclononanen

Azabicyclononanes by Fragmentation, II[1]. – Synthesis of 3‐Azabicyclononanes by Regiospecific (Grob) Fragmentation Clemmensen reduction of the non‐enolizable β1‐dioxo group in the 1‐azaadamantanedione derivative 1 gives the β1‐hydroxy ketone 2, which is converted to the thioesters 3. Treatment of 3a or 3b with nBu3SnH/toluene yields the partially deoxygenated monoketone 4. Chlorination of 2 with SOCl2 generates 6 (geminal dichlorination). Dehalogenation with nBu3SnH produces 5. On the other hand, 2 can be monochlorinated to give 7, selectively. Preparative Grob fragmentation of the aza‐tricyclic skeleton in 7 regiospecifically provides the 3‐azabicyclo[3.3.1]nonane derivative 8. An even better access to 8 from 2 proceeds via an intermediate tosylate.