Switchable Synthesis of Fused Dihydrobenzofuran or Spiro Benzoisoxazole Derivatives Featuring a Migrated or Merged Directing Group

Generating different molecular scaffolds from the same starting materials is an attractive strategy for diversity-oriented synthesis. Presented herein is a switchable synthesis of dihydrobenzofuran-fused indanone or benzoisoxazole spiroindandione based on the cascade reactions of N-phenoxyacetamide with diazo indandione. The selectivity toward different products is expediently manipulated by tuning reaction conditions with the nature of the solvent as a key factor. When the reaction is carried out in DCM, the former is formed through C-H activation (CHA)-initiated [3 + 2] annulation along with acetamide group migration. When the reaction is carried out in DMSO in the presence of a stoichiometric amount of an external oxidant, on the other hand, the latter is generated through CHA-initiated [4 + 1] spiroannulation with directing group retention. In general, this novel protocol features easily tunable selectivity, simple substrates with a broad scope, valuable products with moderate anticancer activity, unique reaction pathways, high atom economy, and ready scalability.