A Dual Arylboronic Acid–Aminothiourea Catalytic System for the Asymmetric Intramolecular Hetero-Michael Reaction of α,β‑Unsaturated Carboxylic Acids

A bifunctional aminoboronic
acid has been used to facilitate for
the first time the intramolecular aza- and oxa-Michael reactions of
α,β-unsaturated carboxylic acids. The combination of an
arylboronic acid with a chiral aminothiourea allowed for these reactions
to proceed successfully in an enantioselective manner to afford the
desired heterocycles in high yields and ee’s (up to 96% ee).
The overall utility of this dual catalytic system was demonstrated
by a one-pot enantioselective synthesis of (+)-erythrococcamide B,
which proceeded via sequential Michael and amidation reactions.