Carbohydrates photochemical radical-addition

Photochemically Initiated, Radical-Addition Reactions to Unsaturated Carbohydrate Derivatives... 

The relative proportions of unsaturated carbohydrate, sensitizer (usually acetone), and solvent may have a decided effect upon a photochemical addition reaction, as at least three competing processes (cycloaddition, radical addition, and energy transfer) are possible. The irradiation of 1 in the presence of 2-propanol and acetone provides an illustration (see Scheme 4). When a small proportion of sensitizer... 

Although there exist numerous ground state reactions, photochemically induci asymmetric radical additions can be very efficient and even highly stereoselectr [125]. Furthermore, no particular functionalization of the starting material is n< essary prior to the formation of a C-C bond. In this context, the photosensiti addition of alcohols, cyclic acetals, and tertiary amines to electron-deficient kenes has been particularly studied. This will be illustrated by a few exampli First attempts to induce chirality in the photoinduced addition of ket radicals (e.g., U) involved a, 3-usaturated carbonyl compounds such as 208 rived from carbohydrates (Scheme 56) [126]. With benzophenone as sensitizi these radicals could be added stereoselectively, and similar reactions were carri out with dioxolane and a, 3-usaturated nitropyranones [127]. 

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