Bronsted base catalysis

This reaction encompasses a number of interesting features (general Brpnsted acid/Bronsted-based catalysis, bifunctional catalysis, enantioselective organoca-talysis, very short hydrogen bonds, similarity to serine protease mechanism, oxyanion hole), and we were able to obtain a complete set of DFT-based data for the entire reaction path, from the starting catalyst-substrate complex to the product complex. 

Bronsted base catalysis is expected to operate when acid-base interaction strongly enhances the substrate nucleophilicity or deeply changes the structure favoring the reaction. The silylation of phosphorous acid with the Me3SiCl-amine system may serve as a good example [Eq. (74)] (see references cited in Ref. 273). The first two molecules of silyl chloride enter the... 

Fig. 15 Heterogeneous Bronsted base catalysis of the Knoevenagel condensation of ethyl cyanoacetate with benzaldehyde using a cross-linked Hu assembly...

General Bransted acid catalysis begins with the addition of a proton whilst general Bronsted base catalysis begins with the removal of a proton ... 

The latter isomerization via an intramolecular hydride shift is catalyzed by Lewis acids. Tin-containing P-zeoHte exhibits remarkable activity for the glucose-fructose isomerization in water. and NMR studies have elucidated this Lewis acid-catalyzed isomerization mechanism, and show a clear difference between Sn-fl (Lewis acid catalysis) and NaOH (Bronsted base catalysis). 

Figure 13.2 Pronucleophile activation under biflinctional Bronsted base catalysis.

Nitroaldol (Henry) Reactions with Bronsted Base Catalysis... 

Br0nsted Base Catalysis Including Bijunctional Catalysis 819 Table 28.7 Direct vinylogous aldol reactions in Bronsted base catalysis. 

Chiral Bronsted base catalysis began with the recognition of a natural product class of compounds in the cinchona alkaloid family [2]. Cinchona alkaloids are templates for Bronsted bases when their quinuclidine nitrogen is protonated by nucleophilic substrates, resulting in a stabihzed chiral intermediate for stereochemical attack of an electrophile. Systematic evaluation of structural variants to the scaffold... 

Bronsted Base Catalysis Including Bifunctional Catalysis... 

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