Small-molecule H-bond donors in asymmetric catalysis.

Asymmetric 1,3-Dipolar Cycloaddition Reactions

Huisgen's 1,3-dipolar cycloadditions become nonconcerted when copper(I) acetylides react with azides and nitrile oxides, providing ready access to 1,4-disubstituted 1,2,3-triazoles and 3,4-disubstituted isoxazoles, respectively. The process is highly reliable and exhibits an unusually wide scope with respect to both components. Computational studies revealed a stepwise mechanism involving unprecedented metallacycle intermediates, which appear to be common for a variety of dipoles.

Copper(I)-catalyzed synthesis of azoles. DFT study predicts unprecedented reactivity and intermediates.

Asymmetric multicomponent reactions involve the preparation of chiral compounds by the reaction of three or more reagents added simultaneously. This kind of addition and reaction has some advantages over classic divergent reaction strategies, such as lower costs, time, and energy, as well as environmentally friendlier aspects. All these advantages, together with the high level of stereoselectivity attained in some of these reactions, will force chemists in industry as in academia to adopt this new strategy of synthesis, or at least to consider it as a viable option. The positive aspects as well as the drawbacks of this strategy are discussed in this Review.

Asymmetric multicomponent reactions (amcrs): the new frontier

140 years ago Adolf von Baeyer proposed the structure of a heteroaromatic compound which revolutionized organic and medical chemistry: indole. After more than a century, indole itself and the complexity of naturally occurring indole derivatives continue to inspire and influence developments in synthetic chemistry. In particular, the ubiquitous presence of indole rings in pharmaceuticals, agrochemicals, and functional materials are testament to the ever increasing interest in the design of mild and efficient synthetic routes to functionalized indole derivatives. This Review emphasizes the achievements in the selective catalytic functionalization of indoles (C-C bond-forming processes) over the last four years.

Catalytic Functionalization of Indoles in a New Dimension

/pdf/a-single-crystal-x-ray-investigation-of-the-structures-of-1qg2g7n7bx.pdf

A Single-Crystal X-Ray Investigation of the Structures of La3(OH)(CrO4)4.3.5 H2O and La2(CrO4)3.7 H2O.

/pdf/preparation-of-single-phases-and-single-crystals-in-the-vq1gemk1uh.pdf

Preparation of single phases and single crystals in the vanadium-gallium-antimony system. crystal structure of v6gasb

Syntheses and structure of dinuclear cobalt(II) complexes of the polypyridine ligand 6,6′-bis[bis(2-pyridylmethyl)aminomethyl]-2,2′-bipyridine

/pdf/on-the-crystal-structures-of-some-phases-in-the-al2o3-nb2o5-1h13md8oti.pdf

On the Crystal Structures of Some Phases in the Al2O3-Nb2O5-System.

A series of four-co-ordinate nickel(II) N2X2 complexes (X = NH, O or S) with tetradentate Schiff-base ligands incorporating pyrazole has been prepared in order to compare the influence on the nickel(II) centre of the donor atoms in N2(NH)2 and N2S2 complexes versus N2O2 complexes. In each case, two identical parts of the ligand are linked by a two- or three-carbon aliphatic chain (n = 2 or 3). Crystal structures have been determined for a n = 3 N2(NH)2 complex, for two n = 3 N2S2 complexes and for a n = 2 N2O2 complex. All of the complexes have been investigated in solution by spectroscopic methods (UV/VIS/NIR, 1H NMR). The n = 2 and 3 N2(NH)2 complexes and the n = 2 N2S2 complexes are fully diamagnetic. An extension of the chain linking the two halves of the ligand from two to three carbon atoms induces a spin-equilibrium process (S = 0 ⇄ S = 1) for the resulting N2S2 complex (ΔG = 19–26 kJ mol–1 at 50 °C). Ligand-field parameters have been derived from the electronic spectra and the electrochemical properties of the N2S2 complexes have been investigated by cyclic voltammetry. From these results it is clear that low-spin character is emphasized in N2(NH)2 and N2S2 complexes of nickel(II) when compared with the corresponding N2O2 complexes.

Rita G. Hazell

Papers

A Single-Crystal X-Ray Investigation of the Structures of La3(OH)(CrO4)4.3.5 H2O and La2(CrO4)3.7 H2O.

Preparation of single phases and single crystals in the vanadium-gallium-antimony system. crystal structure of v6gasb

Syntheses and structure of dinuclear cobalt(II) complexes of the polypyridine ligand 6,6′-bis[bis(2-pyridylmethyl)aminomethyl]-2,2′-bipyridine

On the Crystal Structures of Some Phases in the Al2O3-Nb2O5-System.

Nickel(II) N2X2 Schiff-base complexes incorporating pyrazole (X = NH, O or S): syntheses and characterization†