Magnesium Catalysis in Asymmetric Synthesis

Abstract

In reviewing magnesium-catalyzed asymmetric reactions, we discuss the two general strategies for generating chiral organometallic Mg(II) complexes. Magnesium is one of the most abundant metals on earth and can be applied in a wide range of fundamental asymmetric reactions. However, compared with those of many other metals, the design and application of magnesium catalysts in asymmetric reactions are relatively limited. In this review, we provide insightful discussions of the catalytic strategies associated with Mg(II) catalysts, related mechanism considerations, and current limitations, as well as the opportunities associated with greater focus on magnesium catalysts in chemical synthesis.

Enantioselective Synthesis of Hydrothiazole Derivatives via an Isocyanide-Based Multicomponent Reaction

“…At first, various metal salts were investigated by complexing with chiral N , N′ -dioxide ligand L-RaPr 2 in CH 2 ClCH 2 Cl at 35 °C (Table , entries 1–3). Delightedly, the complex of Mg­(OTf) 2 could promote the desired formal [2 + 1 + 2] cycloaddition reaction smoothly, delivering the corresponding product 4a with good yield and high enantioselectivity (90% yield and 97:3 er; entry 3). Other metal salts were also evaluated, but no better results were obtained (see page S5 in the SI for more details).…”

Enantioselective crossed intramolecular [2+2] photocycloaddition reactions mediated by a chiral chelating Lewis acid

“… 12 The oxygen substituent attached to the carbon atom in α-position to the carbonyl group represents a remarkable and distinct feature of the substrates. Since the formation of five-membered chelates is well established with bidentate Lewis acids, 13 we wondered whether it would be possible to employ a chiral Lewis acid for an enantioselective reaction of 2-(alkenyloxy)cyclohex-2-enones. Based on previous work with chiral Lewis acids as catalysts for photochemical reactions, 14 we had reason to believe that a catalytic enantioselective reaction would be possible if the Lewis acid induced a long wavelength absorption that could be selectively addressed by a proper light source.…”

N-Methylation and Trideuteromethylation of Amines via Magnesium-Catalyzed Reduction of Cyclic and Linear Carbamates

“…Based on the recent developments in Mg-catalysis , and the formation of an unexpected N -methylated product in the reduction of a carbamate (Scheme c vs Scheme b), we started our exploration with linear carbamate 1a as the model substrate, the readily available MgBu 2 as the catalyst, and HBpin as the reducing agent. Initially, different solvents were tested (Table ) and the best results were obtained under solvent-free conditions in which full conversion and a surprisingly excellent yield for 2a were achieved (Table , entry 3).…”