Supramolecular Catalysis: Halogen Bonding and Regulation Strategies Applied to Hydroboration and C-H Functionalization Reactions

The first supramolecular halogen-bonded bisphosphine rhodium(I) complexes were described and then applied to the hydroboration of terminal alkynes towards vinylboronates. The halogen-bonded Rh-complexes displayed enhanced selectivities for the branched vinylboronates. Furthermore, the influence of halogen bonding on other rhodium(I) complexes was studied, observing an unreported halogen-bond-mediated oxidative addition of the C–I bond to the Rh(I) center with formation of cyclometallated rhodium(III) complexes. Finally, new phosphite-based gold(I) supramolecularly regulated complexes were prepared and successfully tested in the selective C–H functionalization of phenols. The regulation principle was proven by combining the phosphite-based gold complex with a suitable regulation agent (up to 20% increase in yield and from 28:1 to >50:1 increase in the selectivity in terms of C-H vs. O-H functionalization products). The results and origin of the regulation effects were rationalized by performing DFT calculations. The utility of the approach was also demonstrated by preparing an advanced synthetic intermediate of the world’s largest selling drug for the hormonal treatment of breast cancer (i.e., Tamoxifen).