Direct catalytic asymmetric aldol reaction of β-keto esters with formaldehyde promoted by a dinuclear Ni2-Schiff base complex

Abstract

A homodinuclear Ni(2)-Schiff base 1 complex (0.1-1 mol%) promoted the direct catalytic asymmetric aldol reaction of beta-keto esters with formaldehyde, giving hydroxymethylated adducts in 94-66% ee.

The direct catalytic asymmetric aldol reaction

“…351 The reaction proceeds with only 0.1–1 mol% catalyst 302 to give the desired adducts in 22–94% yield and in 66–94% ee. The use of formaldehyde as the acceptor component in direct catalytic asymmetric aldol reactions is rare and should prove valuable.…”

A new cyclic binuclear Ni(II) complex as a catalyst towards nitroaldol (Henry) reaction

“…Ni(II) complexes play an important role in various homogeneous catalytic reactions, such as, tetralin oxidation [17], asymmetric aldol reaction [18], Mannich-type and Michael reactions [19] and alkene epoxidation [20], and can also exhibit interesting magnetic properties [21,22]. Some nickel compounds can also act as catalysts towards the Henry reaction under different conditions, namely in homogeneous systems [23], under solvent free microwave conditions [16] or in ionic liquids [24], and high activities (more than 90% yields) are found in a few cases [16,24].…”

Multimetallic Multifunctional Catalysts for Asymmetric Reactions

“…Mn 2 -1b) [22] 94 % ee (TON ~940) (cat. Ni 2 -1b) [26] 9 % ee dr ~>30:1 (cat. Ni 2 -1b) [ [29] NH Boc Boc entity; two distinct metals activate the aldehyde and the nitronate independently.…”

“…Because the Ni 2 -1b complex was bench-stable and can be used without regard to their exposure to air and moisture, hydroxymethylation of b-keto esters using formalin as an electrophile was also successfully achieved. The reaction proceeded with 0.1-1 mol% catalyst, and hydroxymethylated products were obtained in up to 94% ee and 94% yield (TON ¼ up to 940) [26]. For asymmetric Michael reactions, suitable selection of metal was important depending on the combinations of nucleophiles and electrophiles.…”