New C2-symmetric tetrafluorobenzobarrelene ligands were prepared and applied successfully to the rhodium-catalyzed asymmetric addition of arylboronic acids to aromatic aldehydes giving chiral diarylmethanols in high yield with high enantioselectivity.
A rhodium-catalyzed 1,4-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.
Rhodium-catalyzed asymmetric 1,6-addition of arylboronic acids to β-alkynyl acrylamides substituted with a silyl group on the alkyne terminus took place to give high yields of axially chiral allenylsilanes with 94-99% enantioselectivity, which was realized by use of a rhodium/chiral diene complex.
A rhodium-chiral diene complex immobilized on amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin (PS-PEG-diene*-Rh) has been developed. The immobilized rhodium-chiral diene complex (PS-PEG-diene*-Rh) efficiently catalyzed the asymmetric 1,4-addition of various arylboronic acids to cyclic or linear enones in water under batch conditions to give the corresponding β-arylated carbonyl compounds in excellent yields and with excellent enantioselectivity. The catalyst was readily recovered by simple filtration and reused 10 times without loss of its catalytic activity and enantioselectivity. Moreover, a continuous-flow asymmetric 1,4-addition in a flow reactor containing PS-PEG-diene*-Rh proceeded efficiently at 50 °C with retention of high enantioselectivity. Long-term continuous-flow asymmetric 1,4-addition during 12 h readily gave the desired product on a 10 g scale with high enantioselectivity.
Rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to beta-phthaliminoacrylate esters took place efficiently to give high yields of beta-aryl-beta-amino acid esters with 96-99% enantioselectivity, which was realized by use of a hydroxorhodium/chiral diene complex.
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