Titanium silicate molecular sieve, TS-1, catalysed C–C bond formation in Mukaiyama type aldol reactions

Lewis Acids as Catalysts in Oxidation Reactions: From Homogeneous to Heterogeneous Systems

“…In the particular case of TS-1, the spectrum of adsorbed pyridine shows bands at 1605, 1490, 1445 cm -1 associated to adsorption on Lewis acid sites, but not the band at 1545 cm -1 which corresponds to the protonated pyridine. The presence of Lewis acid sites in TS-1 and TS-2 has also been confirmed by other techniques, which also include their activity for Mukaiyama and Michael additions, and Meerwein−Ponndorf−Verley reactions that are typically catalyzed by Lewis acids. ,, In the case of Ti-Beta zeolites, the IR spectra of pyridine adsorbed on two samples of Ti-Beta, one synthesized in OH - and the other synthesized in F - media have been recorded …”

“…The presence of Lewis acid sites in TS-1 and TS-2 has also been confirmed by other techniques, 387 which also include their activity for Mukaiyama and Michael additions, and MeerweinPonndorf-Verley reactions that are typically catalyzed by Lewis acids. 340,370,388 In the case of Ti-Beta zeolites, the IR spectra of pyridine adsorbed on two samples of Ti-Beta, one synthesized in OH -and the other synthesized in F -media have been recorded. 379 The Al-free Ti-Beta synthesized in OH -media with many internal defects and which has a certain hydrophilic character shows bands at 1607, 1490, and 1447 cm -1 associated to pyridine coordinated with Lewis acids, and which are the same bands observed previously for TS-1.…”

“…Thus, owing to the silica framework with little number of defects, the TS-1 is a hydrophobic catalyst that can use H 2 O 2 as oxidant. Using this environmentally friendly oxidant, reactions such as oxidation of alcohols, epoxidation of linear olefins, hydroxylation of aromatics, ammoximation of cyclohexanone, oxidation of alkanes to alcohols and ketones, oxidation of amines, oxidation of sulfur-containing compounds, and oxidation of ethers, among others, have been carried out selectively with TS-1. ,− A summary of the reactions catalyzed by TS-1 is given in Figure .

2 Oxidation reactions catalyzed by TS-1.

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Stereochemical Control in Organic Synthesis Using Silicon-Containing Compounds

“…The normal Mukaiyama aldol reaction, in which the Lewis acid is added to the aldehyde first or is added to the mixture of aldehyde and silyl enol ether, does not therefore take place by way of this kind of intermediate. 320 Other Lewis acids favor the formation of the syn isomer, 321 as also does the use of high pressure 322 or water. 323 In the latter cases reaction takes place by way of a cyclic transition structure in which the silyl group itself acts as the Lewis acid.…”

Cage Like Al-KIT-5 Mesoporous Materials for C–C Bond Formation Reactions Under Solvent Free Conditions

“…Corma and coworkers have reported the same reaction using heterogeneous solid oxophilic Lewis acid catalyst such as Ti-MCM-41 [38]. Zeolytic microporous materials like titanium silicate molecular sieve (TS-1) is also responsible for catalyzing the C-C bond formation in Mukaiyama type aldol and Michael reactions and reported by Kumar et al [39][40][41]. Over this TS-1 catalyst, they were able to report distereoselective syn/anti product in the case of aldol reaction.…”