The Use of α-Diazo-γ-butyrolactams in the Buchner-Curtius-Schlotterbeck Reaction of Cyclic Ketones Opens New Entry to Spirocyclic Pyrrolidones

The only cyclic alpha-diazocarbonyl compound employed in the Buchner-Curtius-Schlotterbeck ring expansion of cyclic ketones to date was alpha-diazo-gamma-butyrolactone. Encouraged by the recent success using.-diazo acetamides in related Tiffeneau-Demjanov type ring expansions, we extended this approach to various alpha-diazo-gamma-butyrolactams, which produced, under BF3 center dot OEt2-promoted conditions, spirocyclic seven-membered ketones. These findings substantially enhance the possibilities offered by cyclic alpha-diazocarbonyl compounds in constructing privileged spirocyclic scaffolds for drug design.