Palladium-catalyzed Asymmetric Hydrosilylation Of Maleimides

The asymmetric hydrosilylation reaction of olefins catalyzed by transition metals is one of the most direct methods for the synthesis of chiral organosilicon compounds.This reaction has the advantages of simplicity,high efficiency,mild reaction conditions,and high atom economy,which has attracted the attention of many researchers.In recent years,chiral organosilicon compounds have developed rapidly in drug molecules and functional materials.The asymmetric catalytic hydrosilylation reaction has become more and more important as well,thus,chiral organosilicon compounds have become one of the hotspots of organosilicon chemistry.So far,researchers have developed a series of relatively complete solutions for the asymmetric hydrosilylation reaction of terminal olefins.In contrast,the asymmetric hydrosilylation reaction of internal olefins and active olefins still lacks an efficient catalytic system.In this paper,we hope to develop an efficient palladium/phosphine catalyst system for the asymmetric hydrosilylation reaction of carbonyl substituted olefins.The details are as follows:(1)Maleimide is an active olefin with carbonyl substituents at both ends of the olefin.Because this type of active olefin has many reaction sites,it is difficult to control the chemical selectivity of the reaction if it is used to hydrosilylation.Therefore,few researches report the hydrosilylation reaction of active olefins.In this paper,palladium metal was used to optimize the reaction conditions,including the screening of chiral phosphine ligands,reaction temperature,reaction solvents and other reaction conditions.The optimal reaction conditions were successfully established,which can synthesize Silicon-based succinimide compound with carbon chiral center efficiently(up to 99%ee).In the derivatization reaction,a series of chiral silylpyrrolidine derivatives can be synthesized through the reduction of the carbonyl group.In the photocatalytic cycloaddition reaction system,we have conceived and realized the generation of a new chiral center with the use of the occupancy effect of the chiral silicon group,a chiral silylazabicyclic compound containing three carbon chiral centers(96% ee,>99:1 dr)was synthesized with high stereoselectivity.(2)The construction of axial chirality in asymmetric hydrosilylation reaction based on maleimide has been investigated.We envisage introducing substituents at the ortho position of N-arylmaleimide to stabilize the atropisomers.After investigating of the ortho-position groups of N-arylmaleimide and optimizing the conditions we found the N-biaryl maleimide is perfectly suitable for the previously established palladium/phosphine catalytic system,which can construct a silyl succinimide compound containing both axial and carbon chiral centers in one step with high stereoselectivity(up to 97% yield,94% ee,99:1 dr).In summary,we have realized for the first time the asymmetric hydrosilylation reaction of carbonyl-substituted olefins(α,β-unsaturated amides).The efficient palladium/phosphine catalyst system can be used to construct both axial chirality and carbon chirality in one step.The silicon-based succinimide compound in the center.In the derivatization reaction,the occupancy effect of silicon has been used to achieve 100%chiral transfer,which provides a new idea for the realization of asymmetric catalysis in the photoreaction system.