Fragmentation of carbohydrate anomeric alkoxyl radicals. A new synthesis of chiral 1-halo-1-iodo alditols

Gonzalez, C.C. and Kennedy, A.R. and Leon, E.I. and Riesco-Fagundo, C. and Suarez, E. (2003) Fragmentation of carbohydrate anomeric alkoxyl radicals. A new synthesis of chiral 1-halo-1-iodo alditols. Chemistry - A European Journal, 9 (23). pp. 5800-5809. ISSN 0947-6539 (https://doi.org/10.1002/chem.200305294)

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Abstract

Treatment of 1,2-fluorohydrins, 1,2-chlorohydrins, 1,2-bromohydrins, and 1,2-iodohydrins of the D-gluco, D-galacto, D-lacto, L-rhamno, D-allo, L-arabino, 3-deoxy-D-gluco, and 3,4-dideoxy-D-gluco families of carbohydrates with the (diacetoxyiodo)benzene/iodine system afforded 1-fluoro-1-iodo, 1-chloro-1-iodo, 1-bromo-1-iodo, and 1,1-diiodo alditols, respectively, in excellent yields. The reaction was achieved by radical fragmentation of the C1C2 bond, triggered by the initially formed anomeric alkoxy radical, and subsequent trapping of the C2-radical by iodine atoms. This methodology is compatible with the stability of the protective groups most frequently used in carbohydrate chemistry. The potential utility of these 1-halo-1-iodo alditols as chiral synthons was evaluated by their transformation into alk-1-enyl iodides and in the Takai E-olefination reaction.