Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination

In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Palladium-catalyzed cross-coupling reactions in total synthesis.

Sol-gel chemistry of transition metal oxides

The design and implementation of cascade reactions is a challenging facet of organic chemistry, yet one that can impart striking novelty, elegance, and efficiency to synthetic strategies. The application of cascade reactions to natural products synthesis represents a particularly demanding task, but the results can be both stunning and instructive. This Review highlights selected examples of cascade reactions in total synthesis, with particular emphasis on recent applications therein. The examples discussed herein illustrate the power of these processes in the construction of complex molecules and underscore their future potential in chemical synthesis.

Cascade reactions in total synthesis.

The Diels-Alder reaction has both enabled and shaped the art and science of total synthesis over the last few decades to an extent which, arguably, has yet to be eclipsed by any other transformation in the current synthetic repertoire. With myriad applications of this magnificent pericyclic reaction, often as a crucial element in elegant and programmed cascade sequences facilitating complex molecule construction, the Diels-Alder cycloaddition has afforded numerous and unparalleled solutions to a diverse range of synthetic puzzles provided by nature in the form of natural products. In celebration of the 100th anniversary of Alder's birth, selected examples of the awesome power of the reaction he helped to discover are discussed in this review in the context of total synthesis to illustrate its overall versatility and underscore its vast potential which has yet to be fully realized.

https://www.ch.ic.ac.uk/local/organic/pericyclic/DA.pdf

The Diels--Alder reaction in total synthesis.

The crystal structures of two adducts of diphenylmercury with neutral bidentate nitrogen donor atom ligands have been determined, showing very weak interactions between mercury and nitrogen atoms. The crystals are disordered in a manner giving rise to diffuse reflexions for which k is odd. The crystal of diphenylbis-(2,4,7,9-tetramethyl-l,10-phenanthroline)mercury(lI) studied has a=21.09, b= 14.54, c= 14.65 A, beta = 120°34', Z=4, and space group Cm. Crystals of diphenylbis(2,9-dimethyl-l,1O-phenanthroline)mercury(II) have a= 15.42, b= 14.28, c= 14.55 A, alpha~beta~gamma 90°, Z=4,and spacegroup PI with approximate Pm symmetry. Both adducts have their planar ligands in (040) with the C-Hg-C units of Ph2Hg moieties aligned in the [010] direction. Each diphenylmercury moiety has one ligand adjacent to it with Hg-N distances of 2.8-3.0 A, and one-half of the ligands in the crystals do not have a mercury atom adjacent to their nitrogen atoms. Within the unit cell of each adduct every second (040) plane has 0·5 occupancy for two Ph2Hg moieties with mercury atoms in those planes, and every other (040) plane has 0·8 and 0.2 occupancy for two Ph2Hg moieties in those planes, giving one Ph2Hg for every two ligands.

The Crystal Structures of Disordered Crystals of Adducts of Diphenylmercury with Bidentate Ligands

Cationic silver compounds with metal (Co, Rh, Ir) tris(dithiocarbamate) and tris(diselenocarbamate) complexes as ligands: synthetic, electrochemical, NMR, electrospray mass spectrometric and X-ray crystallographic studies

Preparation and structure of μ-(2,2′-dipyridylamido-Nα,N:N′)-μ-(2″,2‴-dipyridylamido-Nα′,N″:N‴)bis {bis(pentafluorophenyl)thallium(III)} unexpected formation of a four membered chelate ring

The title compound, which previously had been isolated from bacteria and shown to possess anti-bacterial activity, has been chemically synthesized. The molecular structure has a cis (facial) arrangement of the asymmetric {S,O} bidentate ligands (Fe-S 2.441(1) Ǻ, Fe-O 2.010(1) Ǻ) as required by the crystallographic C3 molecular symmetry. (Crystal data: C6H12N3O3S3Fe, rhombohedral, space group R3, a 7.094(2)Ǻ, α 102.00(1)°, Z 1.) The complex was spontaneously resolved into enantiomers on crystallization and the absolute configuration in the crystal studied was established as Λ by the anomalous dispersion technique. Magnetic, e.s.r. and Mossbauer studies are compatible with a distorted octahedral complex of high-spin iron(III). Cyclic voltammetric studies in acetone of the title compound and some related iron(III) thiohydroxamates were carried out. A reversible FeIII/FeII reduction wave was observed for the N-methylformothiohydroxamato chelate, in contrast to the irreversible reduction of tris(benzohydroxamato)iron(III), a related complex containing an {O,O} chelate. The tris(benzothiohydroxamato) chelate, Fe(PhC(S)NHO)3, which possesses a non-alkylated nitrogen, also showed an irreversible reduction wave.

Structure, absolute configuration and electrochemical properties of Tris(N-methylformothiohydroxamato)iron(III), an antibacterial metal chelate and potential iron siderochrome

Bryan M. Gatehouse

Papers

The Crystal Structures of Disordered Crystals of Adducts of Diphenylmercury with Bidentate Ligands

Cationic silver compounds with metal (Co, Rh, Ir) tris(dithiocarbamate) and tris(diselenocarbamate) complexes as ligands: synthetic, electrochemical, NMR, electrospray mass spectrometric and X-ray crystallographic studies

Preparation and structure of μ-(2,2′-dipyridylamido-Nα,N:N′)-μ-(2″,2‴-dipyridylamido-Nα′,N″:N‴)bis {bis(pentafluorophenyl)thallium(III)} unexpected formation of a four membered chelate ring

Structure, absolute configuration and electrochemical properties of Tris(N-methylformothiohydroxamato)iron(III), an antibacterial metal chelate and potential iron siderochrome

Three-coordinate mercury in (2,2′-bipyridyl)methylmercury(II) nitrate and related complexes