Base-Promoted Reactions of Bridged Ketones and 1,3- and 1,4-Haloalkyl Azides: Competitive Alkylation vs Azidation Reactions of Ketone Enolates

The reactions of 1,3- and 1,4-haloalkyl azides
with enolates of 2-norbornanone (and a ring-expanded
analog) afford polycyclic 1,2,3-triazolines in good yields. The
reaction occurs by the initial azidation of the ketone enolate,
followed in order by triazoline formation and O-alkylation.
An interesting element of this process is the preferential
reaction of the alkyl azide with an enolate anion as opposed
to the more familiar reaction of the alkyl halide (including
Cl and I derivatives). Reactions of acyclic or monocyclic
enolates generally lead to 1,2,3-triazoles but none of the
alternative C-alkylation product.