Thiourea-Catalyzed Addition of Indoles to Aliphatic β,γ-Unsaturated α-Ketoesters

A thiourea-catalyzed addition reaction with indoles to aliphatic beta,gamma-unsaturated alpha-ketoesters has been developed. The easily accessible thiourea aminoindanol derivative makes this approach an interesting alternative for the use of these aliphatic substrates, very scarcely employed in previously reported procedures, highlighting the complementarity of the strategy presented here. The final adducts, which are valuable intermediates for synthesizing the corresponding alpha-amino acid or alpha-hydroxy acid derivatives, are obtained in good yields and enantiomeric excess under mild reaction conditions.