Enantioselective Organocatalytic Synthesis of Sulfur‐Containing Spirocyclic Compounds

Two different enantioselective organocatalytic cascade reactions to form new sulfur-containing spirocyclic scaffolds are described, with moderate-to-high selectivities and the use of N-phenylrhodanine as the bis-nucleophile for these reactions also allowed the formation of the corresponding spirocycles adducts.

Abstract

Abstract Two different enantioselective organocatalytic cascade reactions to form new sulfur‐containing spirocyclic scaffolds are described. In the first approach, benzothiophen‐2‐one and enals react in the presence of a secondary amine catalyst through a Michael/Michael/Aldol sequence to afford the final spiro‐cyclohexene carbaldehydes in good yields (up to 68 %) and with excellent selectivities [20:1 diastereomeric ratio ( dr ), up to 99 % ee ]. In the second approach, the double Michael addition of benzothiophen‐2‐one to aromatic dienones with primary amine catalysis produces the corresponding spiro‐cyclohexanones in good yields (up to 76 %) and with moderate‐to‐high selectivities (up to 12:1 dr , up to 90 % ee ). Moreover, the use of N ‐phenylrhodanine as the bis‐nucleophile for these reactions also allowed the formation of the corresponding spirocyclic adducts.