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Design And Synthesis Of Novel Chiral Quaternary Phosphonium Salts And Application To The Asymmetric Reactions

Posted on:2016-08-27Degree:DoctorType:Dissertation
Country:ChinaCandidate:D D CaoFull Text:PDF
GTID:1221330470457636Subject:Organic Chemistry
Abstract/Summary:PDF Full Text Request
This dissertation focused on the design and synthesis of novel chiral quaternary phosphonium salts based on amino acids, and its application to several asymmetric C-C bond formation reactions as phase-transfer catalysts.This dissertation includes three chapters as following:1. A novel family of amino acids-derived bifunctional thiourea-involved quaternary phosphonium bromides were designed and synthesized employing cooperative catalysis concept to catalyze asymmetric aza-Henry reaction between a-amino sulfones and nitroalkanes under phase-transfer catalysis. Through fine-tuning parameters of the catalysts including chiral backbone, double H-bond and phosphonium center and counteranion, we found that steric-demanding effect of the chiral scaffolds had a positive effect on enantioselectivity, while double H-bond, phosphonium center and counter anion had a little effect. Adducts were obtained in terms of good to excellent yields and enantioselectivies under the optimal conditions, albeit with low diastereoselectivities for substituted nitroalkanes. The catalysts proved to be cooperative catalysis via control experiments, and stable during the reaction based on the31P NMR spectrum analysis.2. A series of the unprecedented multifunctional quaternary phosphonium bromides based on dipeptides were designed and synthesized to mediate the Michael addition-SN2cascade reaction between6(7)-bromo-α, β-unsaturated enones and active methylene compounds under phase-transfer catalysis, which gave access to the desired products with good to excellent yields and enantioselectivities. Strong polar and aprotic solvent N,N-dimethylformamide was necessarily involved to mediate intramolecular SN2reaction after the completion of the first intermolecular Michael addition. On the other hand, extra stronger base Cs2CO3was added besides the addition of N,N-dimethylformamide for the syntheses of six-membered rings. To our delight, ethyl cyanoacetate could also smoothly deliver the cyclo-product without the extra addition of additives. It was noteworthy that chiral six-membered heterocycles could also be synthesized according to the strategy above.3. The newly developed dipeptide-derived multifunctional quaternary phosphonium salts above were employed to catalyze the asymmetric Michael addition of methyl malonates to a, β-unsaturated enones, affording the products in terms of the excellent yields and enantioselectivies. It featured the mild reaction conditions and wide substrate scopes.
Keywords/Search Tags:bifunctional, quaternary phosphonium salts, phase-transfer catalysis, asymmetric catalysis, aza-Henry reaction, cascade reaction, Michaeladdition
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