Organocatalytic, Enantioselective Synthesis of 1- and 3‑Substituted Isochromans via Intramolecular Oxa-Michael Reaction of Alkoxyboronate: Synthesis of (+)-Sonepiprazole

The enantioselective oxa-Michael reaction of alkoxyboronate strategy
was demonstrated to provide a new and practical route to enantioriched
1- and 3-substituted isochromans using a chiral bifunctional organocatalyst.
Furthermore, this methodology was extended to the enantioselective
synthesis of (+)-sonepiprazole, a dopamine receptor antagonist.