Conjugate Additions Using a Water-Soluble Chiral Diene Ligand

Significance

The first example of an asymmetric reaction in water using a chiral diene/metal complex is reported. This work is part of investigations into the generality and reactivity of a new class of chiral bicyclo[3.3.0]diene ligands developed by the same group (J. Am. Chem. Soc. 2007, 129, 5336; Synfacts 2007, 847). Contrasting trends were observed in the nature of arylboronic acids tolerated for cyclic or linear Michael acceptors. Whereas ortho-substituted arylboronic acids gave low enantioselectivity with cyclic substrates 1, they were critical to obtain high enantiomeric excesses with linear substrates 5.