Convenient Enantioselective Hydrosilylation of Ketones Catalyzed by Zinc‐Macrocyclic Oligoamine Complexes

Abstract

Chiral macrocyclic tetra-and hexamine macrocycles derived from trans-1,2-diaminocyclohexane (DACH) in complexes with diethylzinc efficiently catalyze the asymmetric hydrosilylation of aryl alkyl ketones with enantiomeric excess of the product up to 89%. The cyclic structure of the trianglamine ligand increases the enantioselectivity of the reaction, in comparison to the catalysis with the acyclic N,N'-dibenzyl-DACH ligand. Density functional theory (DFT) computations on the structures of ligand-zinc complexes and on the structures of these complexes with a coordinated acetophenone molecule allow us to rationalize the direction of the asymmetric induction of the hydrosilylation reaction as well as the superiority of the cyclic ligand compared to the acyclic one. This is the first example of asymmetric catalysis for the hydrosilylation reaction of ketones with the use of a readily available, inexpensive, and reusable macrocyclic trianglamine ligand.

Rapid Selective Defunctionalization of the Carbonyl Group of α,β-Unsaturated Ketones with Trialkoxylsilane/ZnX2

“…[9][10][11] In a previous paper, 11 we showed zinc salts to be very effective catalysts for the hydrosilylation of ketones. Interestingly, when chalcone was used as a carbonyl substrate under similar conditions, the carbonyl group was reduced to a methylene unit.…”

Practical One-Pot Synthesis of Secondary Amines by Zinc-Catalyzed Reductive Amination

“…In addition, due to the high price and the toxicity less expensive and low toxic metals are highly requested for replacement [36]. Here the use of zinc is probably of great interest [37][38][39][40][41][42][43][44][45][46][47][48][49]. Although several research groups demonstrated the abilities of zinc catalysts in the reduction of imines [50][51][52][53], reductive amination protocols are scarcely reported [54][55][56][57][58][59][60].…”

Mechanism and Enantioselectivity of [Zinc(diamine)(diol)]‐Catalyzed Asymmetric Hydrosilylation of Ketones: DFT, NMR and ECD Studies

“…[24][25][26][27] We [24] and others [28] have recently reported that chiral hexamine macrocycles (trianglamines) [29] derived from DACH, in complexes with diethylzinc, efficiently cata-lyze asymmetric hydrosilylation of aryl alkyl ketones with enantiomeric excess of the product of up to 89 %. [24][25][26][27] We [24] and others [28] have recently reported that chiral hexamine macrocycles (trianglamines) [29] derived from DACH, in complexes with diethylzinc, efficiently cata-lyze asymmetric hydrosilylation of aryl alkyl ketones with enantiomeric excess of the product of up to 89 %.…”

“…[2a,22c,24] Because the reaction mechanism is highly dependent on the catalytic system, the presence of any additive, and the nature of the solvent, the originally proposed mechanism for [Zn(diamine)]-catalyzed hydrosilylation [2a] may not be the same as those proposed for the reactions carried out in the presence of an alcohol. [24,40,44] To this end, we carried out experimental and theoretical studies on the mechanism of [Zn(diamine)-(diol)]-catalyzed hydrosilylation of prochiral ketones, based on NMR and electronic circular dichroism (ECD) measurements as well as on DFT calculations of the possible pathways of reaction. [24,40,44] To this end, we carried out experimental and theoretical studies on the mechanism of [Zn(diamine)-(diol)]-catalyzed hydrosilylation of prochiral ketones, based on NMR and electronic circular dichroism (ECD) measurements as well as on DFT calculations of the possible pathways of reaction.…”