Search

Several new ferrocene derivatives bearing two donor-acceptor systems are reported in which the ferrocene unit has acted both as a donor group and as a rotating spacer. These ferrocene sensors have allowed the naked-eye selective colorimetric detection of copper[II] cation and of benzoate, acetate, or cyanide anions, all anions of special toxicological and biological relevance.

Research was conducted to examine a straightforward asymmetric synthesis of enantiopure 1,2-disubstituted ferrocenes. The strategy is based on a chiral ferrocenyl sulfoxide and consists of a three-step process. The first is the preparation of (r)- or (S)-ferrocenyl p-tolyl sulfoxide from ferrocene. Second is the diastereoselective ortho-functionalization of sulfoxide 2 to sulfoxide 3. Third is introduction of the R2 group. Results show excellent yields for the transformation of 3 -> 4.

The use of chiral catalysts in asymmetric Diels-Alder (DA) reactions is described. DA, a standard method for six-membered ring formation, is suited to the building of stereogenic centers due to its natural cyclic transition state involving suprafacial interaction. But the process becomes practical only with the use ofchiral Lewis acids (LA) to catalyze the DA reaction under mild conditions, allowing very high (90-95%) diastereomeric and enantiomeric excesses. Chiral LAs based on aluminum, titanium, boron and transition metal complexes, as well as non-LA catalysts, are discussed.

Researchers have developed a technique to prepare several enantiomerically pure ferrocenes because of the growing significance of ferrocenes with planar chirality in the synthesis of chiral ligands employed in asymmetric catalysis and synthesis. The technique is effective and economical, involves conveniently removable chiral auxiliary and yields products with predictable absolute configuration.

A modified total synthesis of (S)-goniothalamin is described for an advanced course in organic chemistry. This experiment gives students an opportunity to handle organometallic reagents and perform an enzymatic kinetic resolution and a metathesis reaction, all in the same synthesis. Furthermore, students learn flame-drying techniques for the manipulation of air-sensitive materials and high-performance liquid chromatography handling and analysis, thus strengthening their experimental knowledge. [ABSTRACT FROM AUTHOR]

New ferrocene derivatives bearing two donor-acceptor systems are capable of selectively sensing cations and anions by cooperative binding of the two α,α′-groups bonded to the ferrocene nucleus, thus permitting the naked-eye selective colorimetric detection of copper[Π] cation and acetate, benzoate, or cyanide anions, which are ions of toxicological and biological relevance. [ABSTRACT FROM AUTHOR]

Reports on a study involving the transformation of ferrocenecarboxaldehyde into the acetal of (S)-1,2,4-butanetriol (1,3-dioxane structure) and further methylated to give acetal. What electrophilic quenching provided; Response of controlled hydrolysis; Stereochemistry of the reaction; Discussion on study findings.

Deubiquitinating enzymes (DUBs) are a growing target class across multiple disease states, with several inhibitors now reported. b-AP15 and VLX1570 are two structurally related USP14/UCH-37 inhibitors. Through a proteomic approach, we demonstrate that these compounds target a diverse range of proteins, resulting in the formation of higher molecular weight (MW) complexes. Activity-based proteome profiling identified CIAPIN1 as a submicromolar covalent target of VLX1570, and further analysis demonstrated that high MW complex formation leads to aggregation of CIAPIN1 in intact cells. Our results suggest that in addition to DUB inhibition, these compounds induce nonspecific protein aggregation, providing molecular explanation for general cellular toxicity.

Nootropic compounds are a group of pharmacologically active pyrrolidones. These molecules, which enhance cognition properties and possess a large prescription field, are particularly interesting synthetic targets for the pharmaceutical industry. In this Article, we disclose an effective and environmentally friendly pyrrolidinone synthesis using electrosynthesis. The newly developed methodology includes a Kolbe decarboxylation, followed by an intramolecular radical cyclization and a radical-radical cross-coupling.

Enynes are versatile building blocks in organic synthesis. A copper-catalyzed Hiyama-type cross-coupling of vinylsiloxanes with bromoalkynes is presented. This mild and efficient method led to the formation of various sensitive enynes. The use of cis, trans, and 1,1'-disubstituted vinylsiloxanes was allowed, and full retention of stereochemistry was observed. Sensitive groups such as halides, unsaturated ketones, and aldehydes were fully tolerated.

Monolayers of terpyridine-derivatized silanes were self-assembled, with accurately controlled grafting densities, on single-crystal silicon surfaces. Complexation of the resulting terpyridine monolayers with Pd(OAc)(2) afforded a series of catalytic surfaces covering a full range of Pd loadings (0.14-0.85 nmol.cm(-2)) in the aim to explore their impact on catalysis methodically. X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were combined to afford a precise picture of the grafting density, chemical composition, and catalyst loadings of the surfaces investigated here. We report that the control of the terpyridine density and thus the control of catalytic loadings can be achieved through a fine modification of silanization concentrations, which affords surfaces with tunable catalytic activity.

Photoresponsive monolayers of hydrophilically substituted azobenzenes have been prepared by reaction on aminosilane monolayers on silicon surfaces. Grafting densities in the 0.2-1.0 molecule/nm(2) range were determined by X-ray reflectometry. The monolayers exhibit reversible photoisomerization, switching from a more hydrophilic trans state to a less hydrophilic cis state upon UV irradiation, in contrast with the usual behavior of most azobenzene monolayers that switch from a less to a more hydrophilic state. This indicates that the wettability is not dominated by the change in the dipole moment of the azobenzene moiety but originates from variations in the composition of the outer surface of the monolayers resulting from the reorientation of the substituent groups. The light-driven change in the water contact angle correlates linearly with the grafting density but remains small. However, the wettability contrast can be increased by forcing the molecules to stand in an improved vertical orientation, either by densifying the underlying aminosilane monolayer or by filling the voids left at the bottom of the layer of grafted azobenzene molecules.

A versatile methodology for the diastereo- and enantioselective domino reductive-aldol cyclizations is reported. By using a copper (I)/diphosphane ligand, various five- and six-membered rings were generated with good to excellent diastereo- and enantioselectivities (cis:trans up to 100:0 and ee up to 95%).

[Structure: see text] An efficient method for the enantioselective tandem reductive aldol reaction of methyl acrylate with aldehydes is reported. By using a copper(I) precursor and a proper diphosphane ligand, high reactivities can be reached, with TOF up to 40,000 h-1. Taniaphos-based ligands lead to enantioselectivities of up to 97% in the case of the major syn diastereoisomer.

[Structure: see text] An efficient catalytic system for the three-component coupling of electrophilic alkenes, aldehydes, and silane was optimized with a new family of copper N-heterocyclic carbene complexes. These catalysts do not require activation and show high activity (TOF>15,000 h-1) as well as some anti diastereoselectivity.