Design And Synthesis Of Water-compatible Organocatalysts And Their Applications In Asymmertic Catalyzed Reactions

Asymmetric catalysis is one of effective methods in asymmetric synthesis andplays an important role in the field of organic chemistry. Since the pioneering work ofList, the use of small organic molecules as organocatalysts has received greatattention. As compared with metal catalysts, the organaocatalysts have the advantageof non-toxic, stabilizing, easy operation and so on.Both asymmetric Aldol reaction and Michael addition reaction are powerfulmethods for synthesis of optically active products in organic synthesis. Thebifunctional organocatalysts possess more highly catalytic activities andstereoselectivity because they can activate the electrophilic reagents and nucleophilicreagents simultaneously. So design and sythesis of bifunctional organocatalyst havebeen received increasing interest in recent years. Due to the highly desirableproperties of water in view of its cheap, being safe and environmentally benign,therefore, it is more significant to develop and synthesis of water-compatibleorganocatalystsAccording to the Lewis base-Bronsted acid activation mechanism, we designedand synthesised different types of water-compitable bifunctionally organocatalystswith the use of biphenyl, bipiperidyl as scaffolds and enantiomerically pure α-aminoacids as chiral sources. And these organocatalysts were applied to catalyticasymmetric Aldol reactions and Michael addition reactions. Under the optimizedreaction condition, it was found that the bifunctional organocatalyst41performedwith high efficiencies and showed excellent enantioselectives anddiastereoselectivities in asymmetric Aldol reactions in water (up to99%ee,99:1dr,99%yield). The transition states of the Aldol reactions catalyzed by bifunctionalorganocatalyst41were proposed, and the probable mechanism of chiral induction bythe catalysts was discussed by means of control experiments. The aldol donor wasactivated via the formation of enamine, and aldol acceptor was realized via theH-bond interactions. Bifunctional organocatalysts45-47were applied to asymmetricMichael addition reactions. The organocatalysts45showed highly catalytic activityand stereoselectivity in asymmetric Michael additions reaction in water (up to90%ee,99:1dr,90%yield). The possible catalytic model of transition states for the reactionwas presumed, in this model the Michael donor and Michael acceptor was activatedrespectively by the Lewis base and Bronsted acidIn this work, different types of water-compatible organocatalysts were designedand synthesized by following series reactions. And then they were applied to theasymmetric aldol reactions and Michael addition reactions. It was found that the water-compatible organocatalysts41and45possess some properties ofgreen-chemistry, high activities and high stereoselectivities. It is believed that theseorganacatalysts will be found more promising in other types of asymmetric reactionsin future.