Vilsmeier-Haack-Initiated Formylative Rearrangement of Spirodioxo-lan-5-ones into Functionalized 4,5,6,7-Tetrahydrobenzofurans.

Pharmaceutically relevant bicyclic furans can be synthesized in a single step from substituted dioxolan-5-ones by reacting with Vilsmeier-Haack reagents. These reagents are generated from POCl or PBr and DMF. The reaction cascade is mechanistically complex and involves deoxyhalogenation, iminomethylation, and electrophilic rearrangement steps, which are facilitated by the DMF solvent.