Asymmetric Organocatalytic Friedel-Crafts Alkylation-Cyclization Cascade Reaction of Indoles with o-Hydroxyaromatic α,β-Unsaturated Aldehydes

Abstract

we recently discovered thatimidazolidinone organocatalysts are efficient for the Friedel-Crafts alkylation of indoles with o-hydroxyaromatic α,β-unsaturated aldehydes. During this reaction, the indole reactsthrough conjugate addition with o-hydroxyaromatic α,β-unsaturated aldehyde to give a chiral β-substituted aldehyde,which can be hemiacetalized to a chiral 4-substitutedchroman-2-ol (Scheme 1). Here we report our preliminaryresults from this discovery. The obtained chroman-2-ol caneasily be transform to chroman and derivatives that areubiquitously found in numerous biologically active naturalproducts. Molecules containing chroman scaffolds exhibit abroad range of biological functions, such as antiviral, anti-tumor, and antimicrobial activities.