Synthesis And Application Of Tetraarylphosphonium Salt Supported Chiral Imidazolidin-4-one

In recent years, asymmetric catalysis become one of the main method for the synthesis of chiral material, because of its high efficiency, mild reaction conditions, low usage and repeatable practicality gradually. Chiral imidazolinones as an important organic small molecular catalysts, has been widely used of Diels-Alder cycloaddition,1,3-dipolar cycloaddition, Friedel-Crafts alkylation reaction, indole alkylation reaction and epoxidation reaction in the asymmetric catalytic reaction since MacMillan reported. But, because of its recycling process is multifarious and expensive, it was rarely used in practical application.In order to solve the problem of catalyst’s reuse, supported catalyst is one of the most hopeful solutions. The traditional support was unsolvable inorganic materials, cross linked polystyrene, resin and soluble organic polymers. Among them the soluble organic polymers have been wildly used because it can take part in hemogenous reaction, so it got a very high speed of reaction and could be detect by on-line measuring. Compared with the traditional soluble organic polymer, tetraaryl-phosphonium salt as a soluble support, can fast crystallization, easy purification, was a kind of high performance support in organic synthesis, due to its smaller molecular weight (calculation), high loading capacity, dissolving in CH2Cl2, CH3CN, undissolving in hexane, Et2O.In this paper, we first use the tetraarylphosphonium salts as soluble support and three chiral imidazolinones was synthesized, and this three kinds of phosphonium salt support chiral imidazolinones were used to catalyze the Diels-Alder cycloaddition and1,3-dipolar cycloaddition.By three steps, include quaternary phosphonium reaction, condensation reaction, reduction reaction, using4-bromobenzyl alcohol as the initiating material to synthise dendrimers and altered it to BF4-, PF6-, ClO4-via ion exchange reaction. After that, chiral imidazolinones was react with phosphonium salts and get some catalyst, discussing their solubility, found that dendrimers have poor solubleness and low yeild. So, we choose the4-hydroxymethyl-phenyl-triphenylphosphonium hexafluoro-phosphate as solubility supporter react with three different imidazolinone, and get three different catalysts applied to catalyze the Diels-Alder reaction between unsaturation aldehyde and cyclopentadiene, found the tetraarylphosphonium salt supported5-(4-hydroxy-benzyl)-2,2,3-trimethyl-imidazolidin-4-one has the best catalytic effect. And then discussed the affect of different temperature, solvent, acid addition, reaction time and get the best reaction condition(25℃, CH3OH/H2O=95/5, HC1as acid addition, reaction time was24h). Under the best reaction condition, we used the different substrate to study the different functional group of substrate’s effect to asymmetric Diels-Alder reaction, get decent catalytic effect(Yeild:75%-95%, ee=70%-92%, dr=71/29). These catalysts can be easily separated from the reaction mixture by crystallization, and recycled5times without a significant loss on catalytic activity.We use nitrobenzene as the initiating material to synthise1,3-dipolar by reduction reaction, aldol condensation reaction, and then use tetraarylphosphonium salt supported chiral imidazolinone catalyze1,3-dipolar reaction between unsaturation aldehyde and1,3-dipolar. Discussed the affect of different temperature, acid addition to get the best reaction condition(0℃, nitromethane as solvent, TfOH as acid addition). Under the best reaction condition, we used the different substrate to study the different functional group of substrate’s effect to asymmetric1,3-dipolar cycloaddition reaction, get decent catalytic effect(Yeild:62%-78%, ee=70%-92%, dr=71/29). These catalysts can be easily separated from the reaction mixture by crystallization, and recycled4times without a significant loss on catalytic activity.Tetraarylphosphonium salt was a kind of good soluble carrier, applied to supported Chiral imidazolinone homogeneous liquid phase catalytic Diels-Alder cycloaddition,1,3-dipolar cycloaddition, obtain good catalytic effect, chiral catalyst can recycling reuse.