Spiroazetidine–piperidine bromoindane as a key modular template to access a variety of compounds via C–C and C–N bond-forming reactions

In the context of our ghrelin inverse agonist program, a functionalized bromoindane 3 provided a versatile intermediate for structure–activity relationship studies. After developing operationally simple cross-coupling reactions, a broad spectrum of chemical space was successfully explored. Optimization of a one-pot borylation/Suzuki sequence provided the desired products in high yield with low loading of the palladium catalyst. High yields of N-linked heterocyclic analogues were obtained through palladium catalyzed C–N bond formation. In addition, carboxylation of the bromoindane provided an indane carboxylic acid for further diversification.