Enantioselective β‑Boration of Acyclic Enones by a [2.2]Paracyclophane-Based N‑Heterocyclic Carbene Copper(I) Catalyst

A new planar and centrally chiral bicyclic 1,2,4-triazolium salt has been synthesized from [2.2]­paracyclophane and phenylglycinol. The N-heterocyclic carbene (NHC) copper­(I) complex generated in situ by the reaction of the triazolium salt and Cu2O was an efficient catalyst for the asymmetric β-boration of acyclic enones, producing β-boryl ketones in high yields and enantioselectivities.