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Asymmetric Reactions Of Imines Catalyzed By Organocatalysts Derived From Amino-acid

Posted on:2016-07-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:H Y WangFull Text:PDF
GTID:1221330470957943Subject:Organic Chemistry
Abstract/Summary:PDF Full Text Request
A novel family of phase-transfer catalysts derived from amino acids were designed and synthesized, we also have applied these catalysts in the asymmetric synthesis. Although asymmetric synthesis catalyzed by organophosphine has advanced rapidly over the past decades as a powerful tool for the preparation of various chiral compounds, the type of the reactions that can be catalyzed by organophosphines are very limited. To resolve this problem, we developed a novel strategy of asymmetric dual-reagent catalysis.This dissertation as following:a) Based on the importance of phase-transfer catalysis, we developed a novel family of bifunctional thiourea-ammonium salts derived from amino acids. These phase-transfer catalysts were firstly examined by the asymmetric aza-Henry reactions, we also performed some control experiments to explore the catalytic mechanism. Excellent enantioselectivities and yield could be obtained under the optimized conditions.b) The first synthesis of novel chiral N,S-acetals catalyzed by the novel bifunctional thiourea-ammonium salts was developed by us, these catalysts demonstrated high efficiency in the reaction, which could be carried out on gram-scale with catalyst loading as low as0.1mol%.c) We first realized the application of asymmetric phase-transfer catalysis to the enantioselective addition of TMSCN to ketoimines derived from isatins, and the asymmetric Strecker reaction of the aldimines was also realized by the quaternary ammonium salt derived from amino acid.d) The novel asymmetric dual-reagent catalysis was applied into the Mannich-type reactions, which extended the application scope of the organophosphine catalysis. Under the optimized conditions, this method demonstrated high efficiency in the reaction, and high enantioselectivities and high yields were obtained. The mechanistic studies shed some light on the relationships between catalyst/substrate structures and catalytic efficiency/enantiocontrol.e) The bifunctional organophosphine catalysts were firstly applied in the Strecker reactions of ketoimines and aldimines based on the Lewis basicity of the zwitterion, and the reactions performed well with various substrates, delivering the desired products in excenllent yields and enantioselectivities.
Keywords/Search Tags:Organocatalysis, Phase-transfer catalysis, bifunctional catalyst, organophosphine catalysis, aza-Henry reaction, Strecker reaction, Mannich-type reaction
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