The Michael reaction, with conjugate bases of β-diketones as donors and with α,β-unsaturatedketones as acceptors, is efficiently catalyzed by a combination of clay-supported nickel bromide (heterogeneous) and ferric chloride (homogeneous).
addition and/or conjugate-addition initiated ringclosure products were obtained depending on the reaction conditions. However, unlike 2,4-pentandione, dibenzoylmethane gave only conjugate addition products with Amberlyst-15. When Amberlyst-15-DMAP acetate system was used, always only conjugate addition products were obtained with β-dicarbonylcompounds independent of the reaction conditions.
The LBAs (Lewis acid-assisted Brønsted acidcatalysis) is proposed as possible mechanistic process in the simple FeCl3-catalyzed Michael reactions of chalcones with active methylene compounds in organic solvents. And iron salts were found to be effective promoters in the asymmetricMichaeladdition of 4-hydroxycoumarin to α,β-unsaturated ketone, which resulted in excellent yield and high level of enantioselectivity
New Application of 1,4-Dihydropyridine System: Michael Reactions Mediated by 1,4-Dihydropyridine–Enolate Adduct in Micellar Medium
作者:Sabir H. Mashraqui、Madhavi A. Karnik
DOI:10.1246/cl.2003.1064
日期:2003.11
1,4-dihydropyridine-acetophenone enolate adduct, in catalytic amount effects Michael reactions in aqueous cationic micelles of cetyltrimethylammonium bromide. The enolate, generated by dissociation of the adduct abstracts a proton from readily enolizable substrates to bring about the Michael reaction under mild conditions in fair to good yields without side products.