Radical Reactions of Carbohydrates

Volume II: Radical Reactions in Carbohydrate Synthesis

Chapter 22: Reactions of Carbohydrate Derivatives With Titanocene(III) Chloride

Chapter 22 is in a portable document file (pdf) and can be viewed by clicking the blue, Chapter 22 button below. The drawing underneath the button pictures the formation and reaction of a pyranos-1-yl radical produced from a glycosyl bromide by reaction with titanocene(III) chloride. Beside the drawing is a description of the reaction. Below the drawing and its description is a summary of Chapter 22.

Chapter 22: Reactions of Carbohydrate Derivatives With Titanocene(III) Chloride

Reaction of a glycosyl bromide with titanocene gives a pyranos-1-yl radical.

Drawing Description

Characteristic addition of a nucleophilic radical to a compound with an electron-deficient double bond takes place when halogen-atom abstraction by Cp2TiCl occurs in the presence of methyl acrylate. This type of reaction is pictured in the drawing on the left, which is Scheme 3 in Chapter 22.

Summary of Chapter 22

Titanocene(III) chloride reacts with glycosyl halides and with epoxides to generate carbon-centered radicals. The primary reaction of these radicals is combination with another mole­cule of Cp2TiCl. These radicals also can abstract hydrogen atoms from the solvent or other hydrogen-atom donors in the reaction mixture or undergo radical addition and cyclization reactions. If a radical combines with a second molecule of titanocene(III) chloride, the resulting organotitanium compound typically undergoes a β-elimination reaction. The result of such a reaction usually is formation of a glycal.