Stereoselectivity control in the Rh(I)-catalyzed conjugate additions of aryl and alkenylboronic acids to unprotected hydroxycyclopentenones.

[reaction: see text] The stereoselective Rh(I)-catalyzed conjugate addition reaction of aryl and alkenylboronic acids to unprotected 2-phenyl-4-hydroxycyclopentenone is presented. The free OH group on the substrate is responsible for the stereochemistry, which is cis for arylboronic derivatives. In the case of the alkenylboronic compounds, the stereochemistry can be tuned to either a cis (bases as additives) or trans addition (CsF as additive) without the need of protecting groups.