Enantioselective synthesis of indenopyrazolopyrazolones enabled by dual directing groups-assisted and rhodium(III)-catalyzed tandem C-H alkenylation/[3 + 2] stepwise cycloaddition

The CpXRh(III)-catalyzed asymmetric cascade C-H coupling/intramolecular cyclization of azomethine imines with propargyl carbonates has been developed, affording a variety of chiral tetracyclic indenopyrazolopyrazolone frameworks with good substrate/functional group tolerance and enantioselectivity (up to 97:3 er). Combined experimental studies and DFT calculations revealed the Rh(III)-catalyzed stepwise annulation process and clarified the synergy coordination mode of dual directing groups in tuning the selectivity. By virtue of the azomethine imine moiety and the -OBoc group as synergistic dual directing groups, the enantioselective Rh(III)-catalyzed C-H allenylation/intramolecular [3 + 2] dipolar cycloaddition sequence has been realized for the assembly of tetracyclic indenopyrazolopyrazolone frameworks with specific regioselectivity. [Display omitted]