Silica grafted polyethylenimine as heterogeneous catalyst for condensation reactions

Abstract

Silica graphted polyethylenimine as heterogeneous catalyst for condensation reactions

Control of amine functionality distribution in polyvinylamine/SBA-15 hybrid catalysts for Knoevenagel condensation

“…The band at 1520 cm − 1 is attributed to the N-H deforming vibrations of -NH 3 + [23]. The corresponding stretching vibrations of N-H bonds (3500-3200 cm −1 ) as well as the asymmetric and symmetric stretching modes of C-H bonds (2960-2800 cm − 1 ) are overlapped by the signal from the hydrogen-bonded silanols groups and O-H in adsorbed water [24]. Nevertheless, the weak band attributed to the stretching vibrations of C_O in residual formamide groups is still observed (1665 cm −1 ).…”

Synthesis of (±)‐Pregabalin by Utilizing a Three‐Step Sequential‐Flow System with Heterogeneous Catalysts

“…The Knoevenagel reaction is a carbon–carbon bond‐forming reaction that is catalyzed by bases, and amines such as piperidine have been used as homogeneous catalysts. Although it has been reported that some heterogeneous base catalysts are effective,, only one example of a combination of an aliphatic aldehyde and a malonic acid ester,[5p] such as required here, is known. Moreover, the heterogeneous base catalyst used therein does not necessarily have sufficient activity.…”

Hydrophobic Mesoporous Poly(ionic liquid)s towards Highly Efficient and Contamination‐Resistant Solid‐Base Catalysts

“…Generally, the solvent-free strategy in organic reaction can lead to the development of environmentally benign chemical processes; [56] yet, commonly seen solid-base catalysts, especially those containing only weak Lewis basic sites, are scarcely used for Knoevenagel reaction in the absence of a protic solvent because of their poor catalytic performances. [52,57,58] In previous works, acid-base bifunctional catalysts were designed and exhibited superior performance in solvent-free Knoevenagel reaction. [59,60] In this work, PAMB 1 was evidenced as a medium strong solid base with the base strength of H_ = 18.4~22.5 rather than an acid-base bifunctional catalyst, and at the solvent-free condition it exhibits a much faster catalytic reaction rate than PAMB 1(Br) with only weak amino Lewis basic sites.…”