An Acidic Layered Clay Is Combined with a Basic Layered Clay for One‐Pot Sequential Reactions.

Abstract

4+ exchanged montmorillonite and a hydrotalcite catalyst system are used in a variety of acid and base reactions, such as esterification, acetalization, deacetalization, aldol reaction, Michael reaction, and epoxidation. The catalyst system is easy to prepare and shows high activity and wide applicability and reusability. -(MOTOKURA, K.; FUJITA, N.; MORI, K.; MIZUGAKI, T.; EBITANI, K.; KANEDA*, K.; J. Am. Chem. Soc. 127 (2005) 27, 9674-9675; Dep. Mater. Eng. Sci., Grad. Sch. Eng., Osaka Univ., Toyonaka, Osaka 560, Japan; Eng.) -S. Adam 47-050

Evaluation on the Activity of Surfactant Immobilized and Metal Cation Exchanged Impregnated Montmorillonite Nanoclays on Oxidation of Benzyl Alcohol

“…But the used materials form unwanted bi-products, corrosive, inconvenient to extract from the reaction mixture, non-reusable and difficult to operate. Enhancing environmental contamination and financial restrictions, encouraged chemists to develop fair and high-performance green catalyst [20].…”

On the nature of Ti(IV)‐pillared layered metal hydroxides prepared from green, water‐soluble Ti‐peroxide

“…Layered materials could provide opportunities for developing new materials with a tailored nanodesign, tunable composition and properties, and controlled accessibility to the sites 11–13. Ti(IV)‐pillared montmorillonite materials were prepared14–19 and applied as photocatalysts,14 solid‐acid catalysts,15–16 and gas‐phase oxidation catalysts 20. The preparation methods in most cases involved the use of chloride‐released TiCl 4 14–18.…”

“…Ti(IV)‐pillared montmorillonite materials were prepared14–19 and applied as photocatalysts,14 solid‐acid catalysts,15–16 and gas‐phase oxidation catalysts 20. The preparation methods in most cases involved the use of chloride‐released TiCl 4 14–18. Tungstate‐intercalated,21 Sn‐exchanged,22 V‐pillared,23 and Mo‐loaded21, 24 layered double hydroxides (LDHs) were prepared for the liquid‐phase oxidations of hydrocarbon compounds.…”

A Spatially Orthogonal Hierarchically Porous Acid-Base Catalyst for Cascade and Antagonistic Reactions

“…More sophisticated analogues have employed acid-functionalised mesoporous cores encapsulated by base-functionalised mesoporous shells, 29 or yolk-shell systems with basic amine cores and silica sulfonic acidic shells to increase active site loadings in the shell. 33 However, all such spatially orthogonal catalysts utilise organic acids-bases of limited thermal stability (typically <200 C), 34 and their intrinsic microporosity or mesoporosity 18,35,36 is problematic for the transformation of bulky biomass-derived substrates. Efforts to coat (basic) Mg-Al layered double hydroxide cores with porous (acidic) Al-MCM shells 30 are compromised by entrained alkali from NaOH during synthesis, and limited accessibility of base sites between microporous layers.…”

“…Cooperative aldol condensation via base catalysed condensation and subsequent acid catalysed dehydration is also known. 15 Early attempts at such onepot cascades used physical mixtures of solid acid and base catalysts, 35,61 or co-derivatised materials in which active sites were randomly distributed [62][63][64] and/or partially sacrificed during the catalyst synthesis. 65 Subsequent efforts to partition acid and base functions have employed isolated polymer capsules for enolization-acylation, 66 or non-penetrating dendritic star polymers to encapsulate or isolate separate active sites for iminium, enamine, and hydrogen-bond formation in asymmetric synthesis.…”