**4. In catalysis**

Magnesium oxide is one of the most important metal oxides in catalysis. Though commonly used as support, its employment as a catalyst was also reported in *viz.*, oxidative coupling of methane [10, 11], dehydrogenation–dehydration of alcohols [12], dehydrohalogenation of halogenated hydrocarbons [13], benzylation of aromatics [14], synthesis of pyranopyrazole derivatives [15], and Claisen–Schmidt condensation, etc. [16] Furthermore, the catalytic performance of MgO was improved by promotion by other metals [17] and addition of small amounts of iodine to the reactant mixture [14] for dehydrogenation of short-chain alkanes.

Using alkoxy magnesium Mg(OR)2 and dialkyl magnesium Mg(alkyl)2 species as Grignard reagents in organic synthesis is a fundamental textbook example of organic synthesis [12, 18]. However, the utilization of magnesium as a catalyst in asymmetric synthesis is dramatically undeveloped compared to that of almost all other transitional metals, despite its relatively higher natural abundance than all these other metals combined. Magnesium catalysts are widely used in chemical transformations, and their catalytic use in asymmetric synthesis is highly advisable. For enantioselective reactions, magnesium salts such as Mg(OTf)2, Mg(NTf2)2, and Mg(ClO4)2 are used as Lewis acid catalysts. Different magnesium reagents can give rise to chiral magnesium catalysts. One method involves coordinating complex formation using chiral ligands and a strong Lewis acid magnesium salt, described as "the magnesium catalytic strategy with a fixed magnesium salt" [19].
