Solvent-Free Non-Covalent Organocatalysis: Enantioselective Addition of Nitroalkanes to Alkylideneindolenines as a Flexible Gateway to Optically Active Tryptamine Derivatives
A catalytic asymmetric addition of nitroalkanes to alkylideneindolenines, generated in situ from arylsulfonylindoles, is presented. Despite the weakness of the non‐covalent H‐bond interactions between catalyst and substrates, the performance of the bifunctional organocatalyst used was found to be essentially unaffected by the polarity of the reaction medium. Nitroalkanes, mostly used in nearly stoichiometric
Catalytic asymmetric coupling of vinylogous species <i>via</i> deconjugated butenolide addition to vinylogous imines <i>in situ</i> generated from arylsulfonyl indoles
An efficient catalytic asymmetric coupling of vinylogous species is developed via deconjugated butenolide addition to vinylogousimines in situgeneratedfromarylsulfonylindoles. With quinine-derived bifunctional squaramide as the catalyst, a series of structurally diverse enantioenriched sec-alkyl-3-substituted indoles containing valuable γ,γ-disubstituted butenolide moieties and adjacent quaternary-tertiary