Chiral ruthenium PNNP complexes of non-enolized 1,3-dicarbonyl compounds: Acidity and involvement in asymmetric Michael addition

The chiral complexes [Ru( 2)(PNNP)](2+) (4a) and [ Ru( 3)( PNNP)](2+) (4b), containing the non-enolized 1,3-dicarbonyl compounds 2-((tert-butoxy) carbonyl) cyclopentanone ( 2) or alpha-acetyl- N-benzyl-delta-valerolactam ( 3), were deprotonated to the enolato complexes 5a, b. Complex 4a has a pseudo-aqueous pK(a) Value of 4.6 +/- 0.5 ( with pK(a)(Ph3PH+) = 2.7 as reference) and catalyzes the 1,4-addition of 2 to methyl Vinyl ketone with up to 79% ee.