Enantio- and Diastereoselective Carbonyl-Ene Cyclization-Acetalization Tandem Reaction Catalyzed by Tris(pentafluorophenyl)borane-Assisted Chiral Phosphoric Acids

Highly enantio- and diastereoselective carbonyl-ene cyclization was developed with the use of chiral Lewis acid-assisted chiral Bronsted acid (LBA) catalysts, which were prepared in situ from both sterically demanding tris(pentafluorophenyl)borane and chiral phosphoric acids. Along with the performance of standard carbonyl-ene cyclizations, carbonyl-ene cyclization-acetalization tandem reactions with the use of additional aldehydes were demonstrated with high enantio- and diastereoselectivities. On the basis of mechanistic examinations, a stepwise reaction pathway via tertiary carbocation intermediates involving possible transition states is proposed.

Automated summary

A highly enantio- and diastereoselective carbonyl-ene cyclization was developed using chiral Lewis acid-assisted chiral Bronsted acid (LBA) catalysts, demonstrating high selectivity in both standard and tandem reactions. Mechanistic examinations propose a stepwise reaction pathway involving tertiary carbocation intermediates.