Addition of Heteroatom Radicals to endo-Glycals †

Abstract

Radical reactions have found many applications in carbohydrate chemistry, especially in the construction of carbon–carbon bonds. The formation of carbon–heteroatom bonds has been less intensively studied. This mini-review will summarize the efforts to add heteroatom radicals to unsaturated carbohydrates like endo-glycals. Starting from early examples, developed more than 50 years ago, the importance of such reactions for carbohydrate chemistry and recent applications will be discussed. After a short introduction, the mini-review is divided in sub-chapters according to the heteroatoms halogen, nitrogen, phosphorus, and sulfur. The mechanisms of radical generation by chemical or photochemical processes and the subsequent reactions of the radicals at the 1-position will be discussed. This mini-review cannot cover all aspects of heteroatom-centered radicals in carbohydrate chemistry, but should provide an overview of the various strategies and future perspectives.

Catalytic Radical Reactions of Unsaturated Sugars

“…These methods generally achieve the functionalization of the unsaturated monosaccharides double bond by addition of electrophilic carbon-centered and heteroatom radicals. [14][15][16][17][18][19][20][21][22] Although providing a direct access to densely functionalized glycosides, these traditional methods typically require stoichiometric quantities of oxidants/reductants and/or dangerous and toxic reagents such as radical initiators and UV light irradiation, which limit their applicability and strongly affect their sustainability.…”