Ag(I)-Catalyzed Michael Additions of β-Keto Esters to Nitroalkenes in Water

Significance

The authors have shown water to be a superior solvent for the Michael addition of β-keto esters to nitroalkenes catalyzed by the silver ion: AgOTf/PPh₃. The solvents tested were dichloro­methane, tetrahydrofuran, tetrahydrofuran-water (1:1), no solvent and water. Water gave yields more than 80% higher than the other solvents (or neat conditions). The initial experiments were done with the achiral PPh₃ ligand, but subsequent experiments with (R)-Tol-BINAP gave 77-78% ee. Various β-substituted nitroalkenes and β-keto esters showed good reactivity and reasonable diastereoselectivity.