Diastereo- and enantioselective construction of biologically important pyrrolo[1,2-a]indole scaffolds via catalytic asymmetric [3 + 2] cyclodimerizations of 3-alkyl-2-vinylindoles

Abstract

A catalytic asymmetric [3 + 2] cyclodimerization of 3-alkyl-2-vinylindoles has been established, which efficiently constructed a pyrrolo[1,2-a]indole scaffold with three contiguous stereogenic centers in a diastereo- and enantioselective fashion (up to 98% yield, >95 : 5 dr, 98 : 2 er). This reaction not only represents the first catalytic asymmetric version of this type of [3 + 2] cyclodimerization, but also supplies important examples for using 2-vinylindoles as nitrogen–carbon–carbon (NCC) building blocks in asymmetric catalysis and synthesis. More importantly, this reaction also provides an efficient method for enantioselectively constructing biologically significant pyrrolo[1,2-a]indole scaffolds.