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The assembly of cellulose-based artificial plant cell wall (APCW) structures that contain different types of catalysts is a powerful strategy for the development of cascade reactions. Here we disclose an APCW catalytic system containing a lipase enzyme and nanopalladium particles that transform a racemic amine into the corresponding enantiomerically pure amide in high yield via a dynamic kinetic resolution. [ABSTRACT FROM AUTHOR]

A cascade reaction, consisting of a palladium-catalyzed regioselective aerobic oxidative carbocyclization-borylation of bisallenes and a final aldehyde trapping, afforded triene alcohols with high diastereoselectivity. The cascade reaction occurs under mild reaction conditions and proceeds via an allylboron intermediate that is trapped by the aldehyde in a stereoselective manner. [ABSTRACT FROM AUTHOR]

The versatility of the trityl cation (TrBF4) as a highly efficient Lewis acid organocatalyst is demonstrated in the oxa-Diels-Alder reaction of various unactivated aromatic and aliphatic aldehydes and simple unactivated dienes, such as isoprene and 2,3-dimethylbutadiene. The transformation proceeds smoothly to give 3,6-dihydropyrane adducts in high to moderate yields with catalyst loadings down to 1.0 mol-% under mild reaction conditions. In contrast to most previously reported strategies, this protocol does not require substrate functional group activation, neither by electron-deficient aldehydes (2-oxo aldehydes) or electron-rich dienes (methoxy or amino-butadiene). [ABSTRACT FROM AUTHOR]

A Lewis acid that has received negligible attention as a catalyst is the carbocation. The carbocation is isoelectronic to boron and owes its Lewis acidity to a low-lying empty pC orbital. In terms of reactivity and stability carbocations are very versatile Lewis acids, from the extremely unstable methylium cation to the water-stable tris(N,N-dimethylaniline) methylium ion (crystal violet). Although the Lewis acid properties of carbocations have been extensively studied since the discovery of the tropolium ion more than 130 years ago there is only a handful examples on the application of carbocations as Lewis acid catalysts. Herein, the research on triarylmethylium (trityl)-cation catalysis is summarized. In light of the reports the trityl ion emerges as a highly efficient and highly versatile Lewis acid catalyst capable of catalyzing different classes of reactions often with high selectivity and low catalyst loadings (for some reactions down to ppm levels). [ABSTRACT FROM AUTHOR]

One class of potential Lewis acids that has received negligible attention as a catalyst is the carbocation. Here we show the potential of triarylmethylium ions as highly powerful Lewis acid catalysts for organic reactions. The Lewis acidity of the triarylmethylium ion can be easily tuned by variation of the electronic properties of the aromatic rings and the catalytic activity of the carbocation is shown to correlate directly to the level of stabilization of the empty pC-orbital at the cationic carbon. The versatility of triarylmethylium ions as efficient Lewis acid catalysts for organic reactions is demonstrated in Diels-Alder, aza-Diels-Alder, conjugate addition, halogenation, epoxide rearrangement and intramolecular hetro-ene reactions. [ABSTRACT FROM AUTHOR]

Chiral indolocarbazole dimers fold into a helical conformation by virtue of intramolecular hydrogen bonds, as demonstrated by 1H NMR and CD spectra and optical rotations. In particular, the optical properties of the dimers were found to be extremely sensitive to the nature of the solvent, depending on whether they are folded or not. The helical sense of the dimers can be reversibly switched by binding sulfate ion, which gives rise to complete inversion of the CD spectra. The binding mode and absolute stereochemistry of the sulfate complexes was unequivocally determined by single-crystal X-ray structures, which are all consistent with the CD and 1H NMR spectra in solution. [ABSTRACT FROM AUTHOR]

The versatility of the trityl cation as an efficient Lewis acid organocatalyst is demonstrated in the title process. [ABSTRACT FROM AUTHOR]

Review: [39 refs. [ABSTRACT FROM AUTHOR]

The presented reaction is catalyzed by the Lewis acid tritylium tetrafluoroborate and utilizes unactivated alkenes for the olefination of aromatic aldehydes to give trans β-alkylstyrenes with only acetone as the by-product. [ABSTRACT FROM AUTHOR]

Tritylium tetrafluoroborate is used as a carbocationic Lewis acid catalyst for Diels-Alder, aza-Diels-Alder, conjugate addition, halogenation, epoxide rearrangement as well as intramolecular ene reactions. [ABSTRACT FROM AUTHOR]