Sodium Tetraarylborates as Effective Nucleophiles in Rhodium/Diene-Catalyzed 1,4-Addition to β,β-Disubstituted α,β-Unsaturated Ketones: Catalytic Asymmetric Construction of Quaternary Carbon Stereocenters
A rhodium-catalyzed1,4-addition of sodium tetraarylborates to beta,beta-disubstituted alpha,beta-unsaturated ketones is described. Highly efficient asymmetric catalysis has also been achieved by employing a readily available chiral diene ligand, leading to the construction of quaternary carbon stereocenters with high enantioselectivity.
Chiral Tetrafluorobenzobarrelenes as Effective Ligands for Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboroxines to β,β-Disubstituted α,β-Unsaturated Ketones
and Two Smoking Barrelenes: The rhodium‐catalyzed 1,4‐addition of readily available arylboronic acid anhydrides to simple β,β‐disubstituted α,β‐unsaturated ketones creates quaternary carbon stereocenters with high enantiomeric excesses using a chiraltetrafluorobenzobarreleneligand.
Syntheticroutes to α,α-disubstituted allylamines have been examined. Racemic compounds were conveniently prepared by thermal Overman rearrangements of primary allyl alcohols with trisubstituted double bonds, but rearrangement of these substrates by the only commercially available compound known to catalyze enantioselective Overman rearrangements, the cobalt oxazoline palladacycle (R)-COP-Cl, failed
Rhodium-Catalyzed Asymmetric 1,4-Addition of Aryl Alanes to Trisubstituted Enones: Binap as an Effective Ligand in the Formation of Quaternary Stereocenters
All for one and 1,4‐all: Readily available arylalanes are used in the rhodium‐catalyzed asymmetric conjugate addition reaction with a variety of cyclic and acyclic enones. The enhanced reactivity of the system allows the use of the common binapligand for the generation of quaternary benzylic stereocenters in excellent enantioselectivity (see scheme).