Carbohydrate-Functionalized 1,2,3-Triazolylidene Complexes for Application in Base-Free Alcohol and Amine Oxidation

Acetylglucose- and acetylgalactose-functionalized triazolylideneruthenium(II) and -iridium(III) complexes were synthesized and fully characterized. Subsequent carbohydrate deprotection yielded the first examples of glucose- and galactose-functionalized 1,2,3-triazolylideneiridium complexes. Base-free oxidation of alcohols and amines was used to probe the catalytic potential of the metal complexes and the influence of the carbohydrate wingtip group. Generally, the performance of these complexes is higher in amine oxidation than in alcohol oxidation. While the stereochemistry at the carbohydrate C4 position had no marked influence (galactose vs glucose), the ruthenium complexes typically exhibited higher substrate selectivity and product specificity compared to the analogous iridium species. Most noteworthy is the fact that the catalytic performance is significantly enhanced when the carbohydrate functionality is deprotected, suggesting an active role of the carbohydrate substituent in these transformations.