Effect of support properties on the performance of silica-supported bis(oxazoline)–copper chiral complexes

Mesoporous silica materials with different textural properties have been prepared by sol–gel synthesis under mild acidic conditions, and used as supports for chiral IndaBox ligand. After complexation with copper, these solids are catalysts for cyclopropanation reactions. Enantioselectivities in the range of 52–57% e.e. for cis cyclopropanes and 42–48% e.e. for trans cyclopropanes are obtained without any effect of the textural properties. However, these properties show an important effect on the activity and mainly on the recyclability of the catalyst. In contrast with the expected effect, solids with very large pores but low surface area lead to a significant deactivation upon recovery, whereas solids with highly developed surface area lead to the best overall results.

Graphical abstractMesoporous silicas prepared by sol–gel in the absence of template can be used to immobilize IndaBox. Surface area is crucial for recovery and reuse of the copper complexes in cyclopropanation.Figure optionsDownload full-size imageDownload high-quality image (57 K)Download as PowerPoint slide