Highly diastereo- and enantioselective construction of a spiro[cyclopenta[b]indole-1,3'-oxindole] scaffold via catalytic asymmetric formal [3+2] cycloadditions.

Abstract

An organocatalytic asymmetric formal [3+2] cycloaddition of isatin-derived 3-indolylmethanol with 3-methyl-2-vinylindole has been established, leading to highly stereoselective construction of a spiro[cyclopenta[b]indole-1,3'-oxindole] scaffold with the concomitant creation of three contiguous stereogenic centers (72-99% yield, all >95 : 5 dr, 90-98% ee), one of which is an all-carbon quaternary stereogenic center.