Asymmetric Syntheses of spiro[benzofuro-cyclopenta[1,2-b]indole-indoline] scaffolds via Consecutive Cyclization

An efficient method to construct enantioenriched spiro[benzofuro-cyclopenta[1,2-b]indole–indoline] scaffolds via consecutive cyclization is described here. The new scaffolds possess five successive chiral stereogenic centers and two spiroheterocycles. A range of highly enantioenriched scaffolds has been obtained with up to 93% yield, 99% ee and >19 : 1 d.r. catalyzed by Bronsted acid catalysts.