Rapid Access to Spiro[4.6]-(di)benzodiazepine Indenes: Regioselective Rh(III)-Catalyzed Cascade C–H Activation/Spiroannulation

An efficient one-pot Cp*Rh(III)-catalyzed [3 + 2]-spiroannulation reaction has been developed for the synthesis of potentially biologically relevant spiro[4.6]-(di)benzo[b,e][1,4]diazepine indenes from (di)benzo[b,e]diazepines and ynones/ynoates under mild, operationally simple, and redox-neutral conditions without the need for silver additive or an external oxidant. The process exhibits a broad substrate scope and functional group tolerance, leading to the regioselective synthesis of diverse α-keto/ester-substituted indenamines bearing spirocyclic diazepine frameworks in good to excellent yields. Its synthetic utility was further demonstrated by the modular construction of bioactive ester conjugates using ynoates, highlighting its potential relevance in medicinal chemistry.