Asymmetric Hydrogenation of Tetrasubstituted α,β-Unsaturated Ketones:Access to Chiral 2-Substituted Cyclopentyl Aryl Ketones

Asymmetric hydrogenation of tetrasubstituted alkenes is an important but challenging research topic.Herein,we report an efficient iridium-catalyzed asymmetric hydrogenation of tetrasubstituted α,β-unsaturated ketones for the synthesis of chiral 2-substituted cyclopentyl aryl ketones,an important chiral structural motif for the preparation of chiral pharmaceuticals and bioactive molecules.The reaction proceeded very well with good functional group compatibility and delivered the hydrogenated products in high yields and stereoselectivities(up to 99% yield,>20:1 dr and 99%ee).In addition,the reaction could be carried out on a gram-scale,and all four stereoisomers of the hydrogenated products bearing two contiguous stereocenters were obtained.Furthermore,the hydrogenated product can be transformed into the ERβ agonist Erteberel,and the reaction pathway was also studied via deuterium-labelling experiments.

A boryl-migratory semipinacol rearrangement

The semipinacol rearrangement is one of the classic yet useful synthetic tools in organic synthesis.However,semipinacol rearrangements involving heteroatom-migration are rare.Reported herein is a boryl-migratory semipinacol rearrangement of α-hydroxyallylboronates and α-hydroxypropargylboronates triggered by diverse halogen-,oxygen-,sulfur-and seleniumcontaining electrophiles.The protocol leads to a mild and facile access to organoborons bearing valuable functionalities.The σ(C-B)hyperconjugation is believed to be the key factor that leads to the observed exclusive chemoselectivity and enhanced reactivity.Synthetic utilities of the formed products were demonstrated.