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.