Development of Bifunctional Chiral Thioureas and Thiosquaramides in the Synthesis of Betti Bases

Abstract

Bifunctional thioureas and, for the first time, bifunctional thiosquaramides as organocatalysts were used in the asymmetric Betti reaction involving 1-, 2-naphthols and hydroxyquinoline with N-tosylimine and ketimine. The described methodology affords direct access to chiral aminoarylnaphthols in excellent yield (up to 98%) with high enantioselectivity (up to 80% ee) and enantioenriched 3-amino-2-oxindoles (up to 78% yield, up to 98% ee).

Keywords

• asymmetric organocatalysis
• bifunctional organocatalyst
• thiourea
• thiosquaramide
• Betti bases