Radical Reactions of Carbohydrates

Volume II: Radical Reactions in Carbohydrate Synthesis

Chapter 15: Azides and Azo Compounds

Chapter 15 is in a portable document file (pdf) and can be viewed by clicking the blue, Chapter 15 button below. The drawing underneath the button pictures the azidonitration of a glycal. Beside the drawing is a description of the reaction. Below the drawing and its description is a summary of Chapter 15.

Chapter15: Azides and Azo Compounds

This drawing pictures an azidonitration reaction.

Drawing Description

Azidonitration takes place when the azide radical is produced by oxidation of the azide ion by ammonium cerium(IV) nitrate in the presence of a glycal. The stereoselectivity of azide radical addition is dependent on glycal structure; thus, the azide radical adds in a highly selective fashion to the α face of the D-galactal 8 because the β face is well protected by ring substit-uents. (The drawing shown on the left is eq 9 in Chapter 15.)

Summary of Chapter 15

The principal radical reaction of carbohydrate azides is reduction to tin-substituted amines by reaction with tri-n-butyltin hydride. Products from this reaction are isolated either as free amines or amine derivatives. Three radical reactions for synthesis of carbohydrate azides are known. One of these involves the addition of a carbohydrate radical to ethanesulfonyl azide. A second is the azidonitration that takes place when an azide radical adds to a glycal in the presence of ammonium cerium(IV) nitrate. Finally, reaction of a glycal with an azide radical and diphenyldiselenide, results in azidophenylselenylation.