boron and (2.2)paracyclophane

An enantioselective conjugate addition of boron to α,β-unsaturated ketones catalysed by either a N-heterocyclic carbene or a copper-carbene complex generated in situ from a new chiral bicyclic triazolium based on [2.2]paracyclophane is presented. The dual chiral carbene-copper catalyst has significant advantages over its carbene counterpart as an organocatalyst in asymmetric β-boration of acyclic enones, giving a variety of chiral β-boryl ketones in good yields and enantioselectivities. This is a successful example of employing the same N-heterocyclic carbene in one catalytic reaction as both an organocatalyst and a ligand for transition metal catalysis.

Topics: Boron; Boron Compounds; Catalysis; Copper; Heterocyclic Compounds; Ketones; Methane; Polycyclic Compounds; Stereoisomerism