Asymmetric dearomatization catalysed by chiral Brønsted acids via activation of ynamides.

Chiral Brønsted acid-catalysed asymmetric synthesis has received tremendous interest over the past decades, and numerous efficient synthetic methods have been developed based on this approach. However, the use of chiral Brønsted acids in these reactions is mostly limited to the activation of imine and carbonyl moieties, and the direct activation of carbon-carbon triple bonds has so far not been invoked. Here we show that chiral Brønsted acids enable the catalytic asymmetric dearomatization reactions of naphthol-, phenol- and pyrrole-ynamides by the direct activation of alkynes. This method leads to the practical and atom-economic construction of various valuable spirocyclic enones and 2H-pyrroles that bear a chiral quaternary carbon stereocentre in generally good-to-excellent yields with excellent chemo-, regio- and enantioselectivities. The activation mode of chiral Brønsted acid catalysis revealed in this study is expected to be of broad utility in catalytic asymmetric reactions that involve ynamides and the related heteroatom-substituted alkynes.

Porous Organic Polymer as a Heterogeneous Ligand for Highly Regio- and Stereoselective Nickel-Catalyzed Hydrosilylation of Alkyne.

A porous organic polymer (POL-Xantphos) was synthesized and employed as a heterogeneous ligand for selective hydrosilylation of alkynes. It exhibits high selectivity and catalytic efficiency toward a broad range of alkynes. Owing to the confinement effect of the micropore structure, POL-Xantphos was far superior to the monomeric Xantphos ligands in controlling the selectivity. By performing hydrosilylation in a flow reactor system, separation and regeneration of the Ni/POL-Xantphos catalyst are easily achieved without any loss in selectivity or activity.