Oxidative addition of py(dmgH)₂Co^-Na⁺ to a ribofuranosyl bromide: An unusual reaction with the cobaloxime ligand

Reaction of 2,3,5-tri-O-benzoyl-β-D-ribofuranosyl bromide (12) with NaCo(dmgH)₂py (dmgH = dimethylglyoxime monoanion) in CH₃CN was expected to proceed by normal oxidative addition to the carbon-bromine bond to form 2,3,5-tri-O-benzoyl ribofuranosyl cobaloxime (4) with a carbon-cobalt bond in place of the carbon-bromine bond. Instead, the major products, the isomeric (mixture of α- and β-anomers) dimethylglyoxime adducts 1-O-(dimethylglyoximato)-2,3,5-tri-O-benzoyl-D-ribofuranosides (17), were the result of reaction at the oxygen of the dimethylglyoxime ligand rather than at the cobalt.