Tetralone-2-formylpyrazoles: Valuable Precursors in the Tandem Cyclization for Asymmetric Synthesis of Highly Substituted Spiro-3,4-dihydrocoumarins

Tetralone-2-formylpyrazoles have been synthesized and applied as valuable precursors in a highly stereoselective tandem reaction with 2-nitrovinylphenols catalyzed by a chiral squaramide. This scenario provides a facile strategy to access various highly substituted spiro-3,4-dihydrocoumarins bearing contiguous quaternary and tertiary stereogenic centers with excellent stereoselectivities (>19:1 dr, up to 96:4 er). This reaction represents the first example of novel cyclic pyrazoleamide reagents derived from 1-tetralones being employed as trisubstituted 2-carbon synthons in catalytic asymmetric cyclizations.