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.

Organolanthanoids XIX. The X-ray crystal structures of di [μ-(acetato-O,O:O′)bis(diphenylphosphino-η5-cyclopentadienyl)ytterbium(III)] and di[μ-(acetato-O,O:O′)bis(η5-cyclopentadienyl)ytterbium(III)] - unexpected examples of formal nine coordination in lanthanoid organometallics

The title complex, [Hg(CH3)(C12HllN)]N03,C13HI4HgN+.N03-, 
has a linear C-Hg-N group with Hg-C 2·07(3) and Hg-N 2·10(2) A; there is a weak intramolecular pi interaction between Hg and a C=C bond of the phenyl ring with Hg-C distances of 3·23(2) and 3·33(3) A.

Weak intramolecular π coordination to methylmercury(II). Structure of (2-benzylpyridine)methylmercury(II) nitrate

The structure of the methylmercury complex of 3,3'-dimethyl-2,2'-bipyridyl(L), [MeHg(L)]NO3, was solved by Patterson and Fourier techniques using 1560 counter-measured observed reflections and refined by the full-matrix least-squares method to R = 0·061. The complex has a bent C(1)-Hg-N(1) group [172·7(5)] with Hg-C(1) 2·01(1) and Hg-N(1) 2·11(1) A, weak interaction between mercury and nitrate oxygen atoms, and evidence suggesting the presence of a weak intramolecular-interaction between mercury and the second pyridyl ring, with Hg-C(2') 3·11(1), Hg-N(l') 3·29(1) A and an angle of 100·5 between the planes of the pyridyl rings.

Crystal and molecular structure of (3,3'‐dimethyl‐2,2'‐bipyridyl)methylmercury(II) nitrate; a complex that may have weak intramolecular π‐coordination

Structure and spectral and redox properties of a dioxomolybdenum(VI) chelate of N-methyl-p-tolylthiohydroxamic acid, a complex containing a {O2MoO2S2} donor set

The title compound crystallizes in the monoclinic system with a= 14·07, b= 17·34, c= 19·33 A, β= 91° 3′, Z= 4, and space-group C2/c. The structure was solved by conventional Patterson and Fourier methods and refined by least-squares techniques to R 0·9 for 1218 independent reflections. The compound has a two-fold axis about the methylene carbon atom of the diarsine moiety. Each mercury atom has one arsenic atom within the sum of van der Waals radii from it, and there is a T-shaped distribution of two C6F5 groups and the arsenic atom about mercury with a Hg ⋯ As distance of 3·40 ± 0·02 A and C–Hg–C angle of 173 ± 4°. X-Ray powder diffraction photographs indicate that the compound [(C6F5)2Hg]2Ph2P·CH2·PPh2 has the same structure.

Bryan M. Gatehouse

Papers

Organolanthanoids XIX. The X-ray crystal structures of di [μ-(acetato-O,O:O′)bis(diphenylphosphino-η5-cyclopentadienyl)ytterbium(III)] and di[μ-(acetato-O,O:O′)bis(η5-cyclopentadienyl)ytterbium(III)] - unexpected examples of formal nine coordination in lanthanoid organometallics

Weak intramolecular π coordination to methylmercury(II). Structure of (2-benzylpyridine)methylmercury(II) nitrate

Crystal and molecular structure of (3,3'‐dimethyl‐2,2'‐bipyridyl)methylmercury(II) nitrate; a complex that may have weak intramolecular π‐coordination

Structure and spectral and redox properties of a dioxomolybdenum(VI) chelate of N-methyl-p-tolylthiohydroxamic acid, a complex containing a {O2MoO2S2} donor set

Crystal and Molecular Structure of the 2:1 Adduct of Bis(pentafluorophenyl)mercury(II) and Bis(diphenylarsino)methane