Mutule, I.; Kalnins, T.; Vedejs, E.; Suna, E. Chem. Heterocycl. Comp. 2015, 51, 613-620.
Benzofuro[2,3-b]indolines undergo ring opening in the presence of base to generate 3H-indolines. The latter can rearrange into 3-arylindoles through an intramolecular transfer of the methoxycarbonyl moiety from quaternary carbon to oxygen of phenol. The intermediate 3H-indolines can be isolated upon DMAP-catalyzed O-acylation of the phenol moiety with Boc2O.