Formal C5-Alkylation of Indoles with Donor–Acceptor Cyclopropanes

Installing an indole C5 substituent bearing multiple reactive functional groups, either directly via SEAr or any other methods or during indole construction using classic methods, remains challenging due to the inherently low reactivity at this position or limited functional-group tolerance. Reported herein is a mild, regioselective C5-alkylation of N-alkylindolines with donor-acceptor cyclopropanes (DACs), providing efficient access to C5-alkylated indolines. Selected products were then transformed into the corresponding indoles through a DDQ oxidation-hydrogenation sequence, constituting a formal C5-alkylation of indoles with DACs.