Selective Synthesis of Isochromene Fused Indenone or Indane Fused Indanone Derivatives Featuring with Solvent-Dependent Intra- or Intermolecular O-H Bond Carbene Insertion.

Presented herein is a condition-controlled selective synthesis of isochromene fused indenone (3) or Indane fused indanone derivatives (4) via the cascade reactions of 3-phenyl[1,2,3]triazolo[1,5-a]pyridine (1) with diazo indanedione (2). The formation of products is initiated by Rh(III)-catalyzed aryl C-H alkylation of 1 with 2 followed by denitrogenation of the pyridotriazole moiety to form a Rh-carbene species as the key intermediate. When the reaction is carried out in DCM, the Rh-carbene species undergoes an intramolecular O-H bond insertion with the enol moiety followed by proto-demetalation to give product 3. When the reaction is carried out in HFIP, on the other hand, the Rh-carbene species chooses to take part in an intermolecular O-H bond insertion with HFIP, followed by an intramolecular carbonyl insertion and proto-demetalation to give product 4. To our knowledge, such a solvent-dependent selective O-H bond carbene insertion leading to the formation of distinct polycyclic compounds from the same starting materials has not been reported previously. In general, the protocols developed herein feature high efficiency, good atom/step-economy, broad substrate scope and ready scalability. Moreover, the products could be readily transformed into other valuable products.