Solid-Supported Sodium Azide Reagents: Their Preparation and Reactions with Epoxides

Article abstract of DOI:10.1021/jo00266a023

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 supported NaN3 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 (>90percent).It is deduced that the role 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.