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

Abstract

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.

A bifunctionalized organic–inorganic hybrid silica: synergistic effect enhances enantioselectivity

“…11 Furthermore, the N 2 adsorption-desorption isotherms showed that catalyst 3 was mesoporous due to the sharp adsorption step at higher relative pressure values (0.81-0.98) with a very narrow H1 hysteresis loop (Fig. S5w) 12 while the TEM image with chemical mapping indicated that catalyst 3 was composed of micrometer particles and the iridium centers were uniformly distributed within the nanostructures (Fig. 2, for SEM see Fig.…”

An imidazolium-based organopalladium-functionalized organic–inorganic hybrid silica promotes one-pot tandem Suzuki cross coupling–reduction of haloacetophenones and arylboronic acids

“…Furthermore, the nitrogen adsorption-desorption isotherms (Fig. S4) disclosed that catalyst 3 was mesoporous due to the sharp adsorption step at higher relative pressure values (0.60-0.98) with a very narrow H1 hysteresis loop [32] while the TEM image and TEM with a chemical mapping technique indicated that catalyst 3 was composed of micrometer particles and the palladium centers were uniformly distributive within its nanostructure (Fig. 3, also see the enlarged SEM and TEM in SI in Fig.…”

Imidazolium‐Based Organic–Inorganic Hybrid Silica as a Functional Platform Dramatically Boosts Chiral Organometallics Performance in Asymmetric Catalysis

“…The mesostructural morphology and the distribution of the metallic centers were further investigated using nitrogen adsorption‐desorption techniques and scanning electron microscopy (SEM) with chemical mapping images. The sharp adsorption step at high relative pressure values (0.81–0.98) with a very narrow H1 hysteresis loop (Figure 3 a) shows that the heterogeneous catalyst 3 is mesoporous and composed of micrometer particles 13. SEM images combined with a chemical mapping indicate that Rh centers are uniformly distributed within this IBOIHS material (Figure 2).…”