Contents 1. Introduction………………………………………………………………………………………………... 1 2. Group 2-catalyzed Mannich reactions…………………………………………………………………...... 3 3. Group 2-catalyzed 1,4-addition reactions…………………………………………………………………. 5 4. Silylation of ketones and imines…………………………………………………………………………... 8 5. Hydrogenation reactions using group 13 Lewis acids and frustrated Lewis pairs…………………………12 6. Hydroamination reactions with s-block elements………………………………………………………… 14 7. Aluminum-centered catalysts in phosphonylation reactions……………………………………………… 17 8. Domino reactions…………………………………………………………………..……………………….21 9. Conclusions……………………………………………………………………………………………….. 24 This review highlights a number of recent developments in the field of main group enantioselective catalysis. Many essential transformations can be effected catalytically such as hydrosilylation, hydroamination and hydrogenation reactions, amongst others, in an asymmetric fashion using earth abundant sand p-block elements such as calcium, strontium, boron and aluminum. Recent work in this area has shown that these systems are not only active in catalysis but may also have the potential to compete with transition metal based systems with the reduced cost and toxicity often associated with main group chemistry. Keywords: enantioselective main group catalysis chiral asymmetric | 7 Scheme 8. Catalytic malonate addition reaction using calcium PyBOX complex [66]. Scheme 9. Proposed catalytic cycle of calcium-catalyzed addition reaction to nitro-styrene [66].

The metal‐free catalyst tris(2,4,6‐trifluorophenyl)borane has demonstrated its extensive applications in the 1,2‐hydroboration of numerous unsaturated reagents, namely alkynes, aldehydes and imines, consisting of a wide array of electron‐withdrawing and donating functionalities. A range of over 50 borylated products are reported, with many reactions proceeding with low catalyst loading under ambient conditions. These pinacol boronate esters, in the case of aldehydes and imines, can be readily hydrolyzed to leave the respective alcohol and amine, whereas alkynyl substrates result in vinyl boranes. This is of great synthetic use to the organic chemist.

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Controlling the reactivity of transition metals using secondary, s-accepting ligands is an active area of investigation that is impacting molecular catalysis.H erein we describe the phosphine gold complexes [(o-Ph 2 P(C 6 H 4 )Acr)AuCl] + ([3] + ;A cr = 9-N-methylacridinium) and [(o-Ph 2 P-(C 6 H 4 )Xan)AuCl] + ([4] + ;X an = 9-xanthylium) where the electrophilic carbenium moiety is juxtaposed with the metal atom. While only weak interactions occur between the gold atom and the carbenium moiety of these complexes,t he more Lewis acidic complex [4] + readily reacts with chloride to afford at rivalent phosphine gold dichloride derivative (7)i nw hich the metal atom is covalently bound to the former carbocationic center.This anion-induced Au I /Au III oxidation is accompanied by aconversion of the Lewis acidic carbocationic center in [4] + into an X-type ligand in 7.W ec onclude that the carbenium moiety of this complex acts as alatent Z-type ligand poised to increase the Lewis acidity of the gold center,anotion supported by the carbophilic reactivity of these complexes.