Access to Fused Tricyclic γ‑Butyrolactones, A Natural Product-like Scaffold

Serendipitous findings
of an acid mediated skeletal rearrangement
of bicyclo-β-ketoester having cyclopropyl ring to access fused
tricyclic γ-butyrolactones has been described. This novel transformation
has been optimized to 30 mol% p-toluenesulfonic acid
(p-TSA) in toluene using Dean–Stark apparatus,
where the aldol condensation, cyclopropyl ring opening followed by
cyclization took place in a single-pot operation. The resulting tricyclic
compounds are interesting chemotype with natural product resemblance
and may find useful applications in the future.