SOLID-SUPPORTED SODIUM-AZIDE REAGENTS - THEIR PREPARATION AND REACTIONS WITH EPOXIDES
SOLID-SUPPORTED SODIUM-AZIDE REAGENTS - THEIR PREPARATION AND REACTIONS WITH EPOXIDES
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DOI：
10.1021/jo00266a023
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发表时间：
1989-03-03
影响因子：
3.6
通讯作者：
IZUMI, Y
中科院分区：
文献类型：
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作者：
ONAKA, M;SUGITA, K;IZUMI, Y
叠氮化钠负载在三种类型的多孔固体酸（沸石，氧化铝和硅胶）上，并应用于与环氧化物的几种反应。系统的研究表明，负载试剂的反应活性受NaN 3的负载量，试剂中的吸附水量，固体酸的酸性和反应溶剂的影响很大。为了证明负载型NaN_3试剂在选择性有机合成中的应用，研究了2，3-环氧醇与负载型试剂的亲核开环反应。在负载的试剂中，仅Ca 2+交换的沸石负载的试剂以高度区域选择性的方式（> 90%）诱导C-3开环。推测钙离子在沸石中的作用是通过与钙离子形成螯合物，提高沸石的酸强度，促进环氧化物的开环，并固定环氧醇的构象。
Sodium azide is supported on three types of porous solid acids (zeolite, alumina, and silica gel) and applied to several reactions with epoxides. A systematic investigation reveals that the reactivities of the supported reagents are greatly influenced by loading amounts of NaN3, amounts of adsorbed water in the reagents, acidic properties of the solid acids, and reaction solvents. For demonstrating the utility of supportedNaN3 reagents in selective organic syntheses, nucleophilic ring-opening reactions of 2, 3-epoxy alcohols with the supported reagents are examined. Among the supported reagents, only the Ca2+-exchanged zeolite-supported reagent induces a C-3 ring opening in a highly regioselective manner(> 90%). It is deduced that therole of calcium ions in the zeolite is to increase the acid strength of the zeolite facilitating the ring cleavage of epoxides and to fix the conformation of epoxy alcohols through forming chelate complexes with calcium ions.