Multistep Phase-Switch Synthesis by Using Liquid-Liquid Partitioning of Boronic Acids: Productive Tags with an Expanded Repertoire of Compatible Reactions
作者:Sam Mothana、Jean-Marie Grassot、Dennis G. Hall
DOI:10.1002/anie.200906710
日期:2010.4.6
Tagging along: A system for phase‐switch synthesis has been developed. The boronicacid functionality is used as a phase tag that complexes to sorbitol and facilitates compound transfer from an organic solvent to water at high pH. The phase tag can then be used in a productivereaction step to generate targeted products, thereby eliminating purification by silica gel chromatography.
This work describes the preparation and characterization of a library of alginate-supported palladium nanoparticles together with their catalytic capabilities to promote the Suzuki-Miyaura reaction. Using the chelating properties of the carboxylate functions of the alginate matrix a series of Ca, Ba, Mn, Zn, Ni, Ce, Cu, and Co alginate gels were first prepared and then reacted with Pd2+ salts. Partial exchange of metal cations followed by Pd reduction into palladium nanoparticles and supercritical CO2 drying generated a panel of bimetallic alginate aerogels. Physical characterizations of these materials showed a significant influence of both the gelling metal nature and the Pd loading on surface areas and nanoparticles size. A comparative study of the catalytic performances of these heterogeneous catalytic systems is then reported for the Suzuki-Miyaura reaction. This study highlighted the superior performances of palladium nanoparticles supported on copper-alginate aerogels. This heterogeneous catalyst showed high catalytic activities as illustrated by a TOF value of 10 s(-1) and a TON value close to 10(6). The robustness of the catalyst allowed several reuses with no significant loss of activity or metal leaching.