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

Synthesis and properties of novel cobalt(III) and nickel(II) complexes with coordinated azetidine nitrogens: crystal structure of mer-tris(3-(aminomethyl)-3-methylazetidine)cobalt(III) chloride

/pdf/the-crystal-structure-of-rubidium-triselenocyanate-2e1df6mxqc.pdf

The Crystal Structure of Rubidium Triselenocyanate Hemihydrate.

Etude de la reduction electrochimique du disulfure de carbone en presence de monosulfure de carbone. Structure cristalline du (bis-methylthiomethylene-2 dimethylthio-4,5) dithiole-1,3, forme par methylation du tetrathiooxalate

/pdf/the-role-of-carbon-monosulfide-in-the-electrochemical-2z1q577xp0.pdf

The role of carbon monosulfide in the electrochemical preparation of 4,5-bis(methylthio)-1,3-dithiole-2-thione

Bis(bidentate ligand) and tetradentate ligand nickel(II)
N
 2
X
 2
 Schiff-base and aza complexes
(X = NH or S) have been prepared and their properties
investigated by spectroscopic methods. In the bis(bidentate ligand)
complexes the aza function stabilizes the low-spin
S = 0 state compared with the imine function. The
aza complexes are low spin both in the solid state and in solution; the
Schiff-base complexes are either low or high spin
(S = 1) in the solid state, and are either in
spin equilibrium
(S = 0 ⇌ S =
 1) or high spin in solution. The
crystal structure has been solved for the high-spin complex
bis(4-isopropyliminomethyl-1,3-diphenylpyrazol-5-ylaminato)nickel(
II). The co-ordination of Ni is pseudo-tetrahedral, the angle
between the N–Ni–NH and
NH′–Ni–N′ planes being 93.8(1)°. The
Ni–N (imine) bond lengths are 1.999(2) and 2.003(3) A,
significantly longer than the Ni–N (amine) bond lengths of
1.919(2) A. In the tetradentate ligand complexes the two identical
halves of the ligands are linked by aliphatic four-carbon chains. When
the linkage is
CMe
 2
(CH
 2
)
 2
CMe
 2
 the complexes
are fully paramagnetic in the solid state and in solution, while
complexes bridged by unsubstituted (CH
 2
)
 4
 are low
spin in the solid state and in spin equilibrium in solution. The crystal
structure of
[N,N′-bis(1,3-dimethyl-5-sulfanylpyrazol-4-
ylmethylene)butane-1,4-diaminato]nickel(II) reveals an almost
planar co-ordination geometry, the angle between the
N–Ni–S and S′–Ni–N′ planes being
7.9(3)°. The Schiff-base complexes are chiral and all show evidence
of racemization in solution. Thermodynamic parameters for the
spin-equilibrium process in CD
 2
Cl
 2

[ΔG(25 °C) from -4.32 to 0.71 kJ
mol
 -1
 for the bis(bidentate ligand) systems, from 3.72
to 11.3 kJ mol
 -1
 for the tetradentate ligand systems]
and kinetic parameters for the racemization process in
CD
 2
Cl
 2
 or CDCl
 2
CDCl
 2

[ΔG
 ‡
(25 °C) from
40.5 to 53.3 kJ mol
 -1
 for the bis(bidentate ligand)
complexes, 46.5 to 63.1 kJ mol
 -1
 for the tetradentate
ligand complexes] have been derived using variable-temperature

 1
H NMR spectroscopy. Sulfur donor atoms and aryl substituents
favour the low-spin state. Ligand-field parameters for the Schiff-base
complexes have been derived from the electronic spectra.

Racemization kinetics and spin states of four-co-ordinatenickel(II) N2X2 Schiff-base and azacomplexes with bi- or tetra-dentate ligands incorporating pyrazole(X = NH or S)

Rita G. Hazell

Papers

Synthesis and properties of novel cobalt(III) and nickel(II) complexes with coordinated azetidine nitrogens: crystal structure of mer-tris(3-(aminomethyl)-3-methylazetidine)cobalt(III) chloride

The Crystal Structure of Rubidium Triselenocyanate Hemihydrate.

The role of carbon monosulfide in the electrochemical preparation of 4,5-bis(methylthio)-1,3-dithiole-2-thione

Racemization kinetics and spin states of four-co-ordinatenickel(II) N2X2 Schiff-base and azacomplexes with bi- or tetra-dentate ligands incorporating pyrazole(X = NH or S)

A new polymorph in the zinc phosphate Zn2(HPO4)3 family prepared with DABCO as structure-directing agent