One potential Lewis acid that has received negligible attention as a catalyst is the carbocation. Here we show the potential of triaryl methylium ions as highly powerful Lewis acid catalysts for organic reactions. The Lewis acidity of the triaryl methylium ion can be easily tuned by variation of the electronic properties of the aromatic rings and the catalytic activity of the carbocation is sho...

The silica boron sulfuric acid nanoparticles (SBSANs) as an efficient heterogeneous solid acid catalyst with both Brønsted and Lewis acidic sites catalyzed the preparation of bis-4-hydroxycoumarin derivatives using reaction of aldehydes and 4-hydroxycoumarin under mild and solvent-free condition at room temperature. This new and efficient methodology has advantages in comparison with currently ...

Dimerisation of alpha-olefins by a catalyst system comprising of a bis(imido) tungsten compound and a Lewis acid component has been investigated by density functional theory employing a catalyst model that closely mimics the real system together with ethylene chosen as a prototypical substrate. This study disclosed that the Lewis acid preferably forms four-membered chelates by bridging across t...

A new heterogeneous catalyst, hydrophobic TiO4-deposited mesoporous silica, has been designed for the efficient Mukaiyama-aldol condensation, a water-participating Lewis acid-catalyzed reaction between a hydrophobic carbonyl compound and silyl enol ether. The prepared catalyst suspended in water exhibited high catalytic performance as a reusable catalyst for the reaction without a surfactant.

a rapid and efficient one-pot, four-component protocol towards the synthesis of polyhydroquinoline derivatives has been developed. the condensation of aldehyde, dimedone, ethyl acetoacetate and ammonium acetate in presence of stannous chloride was carried out under solvent free condition to synthesize a variety of polyhydroquinoline derivatives in good to excellent yields. stannous chloride was...

We report a novel Lewis acid catalysed tandem reaction of isocyanides, chromone 3-carboxylic acid and nucleophiles. An experimentally very simple procedure, involving the use of microwave irradiation in the presence of a Lewis acid catalyst, affords a representative collection of chromone-2-carboxamides and chromone-2-carboxamido-3-esters in high yields, in just a few minutes. Such an unprecede...

One possible way to take advantage of such abilities may be to apply a ‘combined acids system’ [2] to the catalyst design. The concept of combined acids, which can be classified into Brønsted acid-assisted Lewis acid (BLA), Lewis acid-assisted Lewis acid (LLA), Lewis acid-assisted Brønsted acid (LBA), and Brønsted acid-assisted Brønsted acid (BBA), can be a particularly useful tool for the desi...

Chiral supramolecular boron Lewis acid catalysts were developed with the use of chiral 3-phosphoryl-BINOLs, 2-cyanophenylboronic acids, and tris(pentafluorophenyl)borane based on CN···B and PO···B coordination bonds. In particular, coordinated tris(pentafluorophenyl)boranes can increase the Lewis acidity of the active center based on the Lewis acidassisted Lewis acid catalyst system. A possible...