Annual Reports Section "B" (Organic Chemistry) (v.107, #00)

Front cover (1-2).

Contents list (3-14).

Introduction by Phil Page; Ian Cunningham, Scientific Editors (15-18).

Two topics continue to dominate radical chemistry; the search for cleaner, more efficient methods to generate radicals, and improving enantioselectivity in radical reactions. The use of photoredox catalysts that rely on visible light to promote the formation of alkyl radicals has great potential to allow radical chemistry to gain more widespread acceptance. The research of Stephenson and others has shown that this chemistry can mediate many traditional radical transformations. Three groups have reported truly green methodology for the formation of acyl radicals that simply requires water and air. MacMillan’s enantioselective organocatalytic radical chemistry continues to push the boundaries of asymmetric synthesis; this year has seen it used in a radical-ion crossover cascade for the synthesis of carbocycles and in a number of remarkable polyene cascade cyclisations. The latter includes a hexacyclisation that installs 11 contiguous stereocentres with high diastereo- and enantioselectivity.

Synthetic methods Part (II): oxidation and reduction methods by Syeda Farina Asghar; Simon E. Lewis (34-67).
This Report highlights advances in some of the most commonly used oxidation and reduction reactions, focusing on the literature from 2010. The review is subdivided in a similar fashion to the authors' previous reviews in this area (S. E. Lewis, Annu. Rep. Prog. Chem., Sect. B: Org. Chem., 2010, ref. 1; S. E. Lewis, Annu. Rep. Prog. Chem., Sect. B: Org. Chem., 2009, ref. 2). Several standout advances have been reported. In the field of oxidation, Yamamoto has reported methods for the reliable enantioselective epoxidation of homoallylic and bishomoallylic alcohols (H. Yamamoto, J. Am. Chem. Soc., 2010, ref. 20) an area hitherto underdeveloped in comparison with allylic alcohol oxidation. Tomkinson has developed a dihydroxylation of alkenes which employs a readily prepared, stable malonyl peroxide as oxidant, the significance of which is highlighted by the lack of other metal-free methods to effect the corresponding transformation (N. C. O. Tomkinson et al., J. Am. Chem. Soc., 2010, ref. 53). In the field of reduction, Tsuji has reported a catalytic system that is particularly effective for the reduction of highly hindered ketones and even exhibits selectivity for more hindered ketones over less hindered ones (Y. Tsuji et al., Angew. Chem., Int. Ed., 2010, ref. 197). Also in the area of ketone reduction, Matsuo has demonstrated reduction of ketones by 1,3-diols in an unusual metal-free process catalysed by a sulfonic acid; high levels of stereoinduction are achieved when a homochiral diol is employed as reductant (J.-I. Matsuo et al., Tetrahedron, 2011, ref. 225; J.-I. Matsuo et al., Org. Lett., 2010, ref. 226).

Heteroatom methods by Jonathan P. Knowles; Andrew Whiting (68-90).
The report deals with some advances in organo-oxygen, -nitrogen, -boron and -silicon chemistry from 2010.

Organometallic chemistry by John S. Fossey (91-101).
Highlights from the organometallic chemistry literature appearing in 2010 are surveyed. Selected and exemplary reports are compiled including comment on the 2010 Nobel Prize for chemistry, gold chemistry and copper-catalysed so-called “click” reactions.

Organocatalysis by Benjamin R. Buckley; Mohamed M. Farah (102-117).
Reactions carried out with substoichiometric quantities of organic molecules as catalysts have received much attention over the past decade. This review highlights progress in 2010 towards highly enantioselective organocatalytic systems and the natural product/biologically active compounds that can be prepared using these types of processes.

Heterocyclic chemistry by Karl Hemming (118-137).
2010 offered highlights in pericyclic chemistry, particularly 1,3-dipolar cycloaddition chemistry, asymmetric synthesis, gold catalysis, organocatalysis, hydroamination, C–H activation and multicomponent reactions.

Marine natural products by Robert A. Hill (138-156).
This review covers the literature on marine natural products published in 2010. Natural products from a variety of marine sources with unusual structural features or interesting biological activities are highlighted. The compounds are organised loosely under their biogenetic origins of polyketides, terpenoids, alkaloids and peptides. In 2010 several marine natural products with with complex structures have been identified and biosynthetic pathways proposed for their formation.

Highlight syntheses by Nadale K. Downer-Riley; Yvette A. Jackson (157-181).
This review showcases some exemplary total syntheses of natural products reported in the scientific literature in 2010.

Supramolecular chemistry by Scott J. Dalgarno (182-198).
The year 2010 has seen many advances in supramolecular chemistry. This short review highlights a number that have been made by various research groups. In line with previous articles from this series, the review is split into three broad sections encompassing molecular recognition, structure and assembly, and functional systems.

Biotransformations by Gideon Grogan (199-225).
This report reviews significant developments in applications of biological catalysis in synthetic organic chemistry for the year 2010. Hydrolases have been applied in kinetic resolution and quantitative DKR processes and have been evolved in vitro to give enzymes displaying improved enantioselectivity and solvent stability. Applications of reductases have included an unusual instance of the generation of optically active atropisomers and also the identification of stereoselective imine reductases in Streptomyces spp. Other biotransformations leading to optically active amines have focused on transaminases, and a wide-ranging genomics analysis has revealed nineteen new and previously rare (R)-selective transaminases. A further (R)-selective transaminase was extensively engineered for process suitability for application in the industrial synthesis of sitagliptin. Improved carbon–carbon bond formation by aldolases is being addressed through the identification and improvement of enzymes accepting non-phosphorylated dihydroxyacetone as a substrate donor for the synthesis of sugars. In addition, new enzymatic activities, including natural enzymes that catalyse the Stetter reaction, and also the Michael-type addition of water to cyclohexenone have been reported. Finally, advances in the in silico design of enzymes are proceeding rapidly, with the report of the design of the first enzyme known to catalyse an bimolecular Diels-Alder reaction.

The field of nucleophilic carbenoid ligands in organometallic catalysis is continuously expanding with new chemical transformations and improved catalytic systems. This review highlights just few developments of the last year. Out of several hundred scientific papers that covered the subject last year, the authors limit themselves to the reports that present direct catalytic results and, at some extent, interesting stoichiometric reactions or mechanistic aspects with obvious applicability in catalysis.

In this chapter the major advances in the chemistry of radicals and radical ions reported in 2010 will be presented from a mechanistic point of view. In the first part recent developments in the area of synthetic methodology, ranging from hydrogen atom transfer, oxidative and reductive processes as well as rearrangement and tandem reactions will be outlined. Advances in the understanding of the role of radicals and radical ions in biological systems will be described in the second part of this report.

Reaction mechanisms: pericyclic reactions by Dean J. Tantillo; Jeehiun K. Lee (266-286).
This report surveys the 2010 literature on mechanisms of pericyclic reactions. Among the newer concepts highlighted in this year's studies are the distortion-interaction model of reactivity, the importance of CH-π interactions in controlling selectivity, and the catalysis of pericyclic reactions by transition metals and organocatalysts. This year, a substantial number of (4+3) cycloadditions and dyotropic rearrangements were examined; these reactions have received limited attention in the past.

Reaction mechanisms: polar reactions by Anna K. Croft; Erika Davies (287-307).
This review presents highlights from papers published in 2010 reporting the mechanistic studies of polar reactions across a diverse range of fields, and is primarily focussed on experimental investigations. A number of examples related to biological systems are included, where the reaction mechanisms are often both complicated and enhanced by supramolecular factors. The breadth of modern physical organic chemistry means that the subheadings used throughout the review should be used as guidelines, as for many studies it is possible to categorise them in a number of different ways.

NMR spectroscopy continues to evolve, with publications in 2010 providing an eclectic collection of applications, advances and incremental improvements. A new 45 MHz NMR spectrometer was announced by PicoSpin: the world's first high-resolution NMR spectrometer that has the “foot-print” of a shoe-box. It is a programmable pulse-FT system that uses a permanent magnet and a flow-capillary sample delivery system. I am indebted to the great and the good whose work has been reported here, all credit is theirs; errors, omissions and blame are all mine.

Reactivity in organised assemblies by Niklaas J. Buurma (328-348).
This report reviews the 2010 literature on reactivity in organised assemblies in aqueous systems. Although the basic scope of the report is broadly as before, this year's themes have been divided as follows: (1) reactivity in micelles, including medium effects and compartmentalisation, micelle-assisted catalysis and functionalised amphiphiles, (2) DNA-based approaches to influence reactivity, including DNA-templated reactions and DNA-based catalysis, (3) nanoparticle-based assemblies for use in catalysis including modulating nanoparticle catalysis through thermoresponsive polymer shells and nanoparticle-supported catalysts and (4) spatial organisation for directed sequential reactivity.

Computational organic chemistry by Steven M. Bachrach (349-368).
The 2010 literature pertaining to computational organic chemistry is summarized and reviewed. Highlights include the novel structure of the propellane radical cation, the putative claim for the preparation and characterization of 1,3-dimethylcyclobutadiene, new annulenes with Möbius topology, tunneling within phenylhydroxycarbene, a new method for using computed NMR spectra to identify structure, and a new model to rationalize the protobranching effect.

Enantioselective catalysis by Ai-Lan Lee (369-389).
The following review highlights significant advances in the field of enantioselective catalysis in 2010. Key advances in enantioselective gold-catalysed reactions, palladium-catalysed Heck reactions and alkene metathesis will be emphasised.

Bioinspired organic chemistry by Salvador Tomas (390-413).
This Annual Report reviews a selection of contributions from researchers in the field of organic chemistry broadly interpreted, which take inspiration from biomolecular systems. The report is divided in three sections: the first two sections discuss progress in organic chemistry inspired by nucleic acids and proteins. The third section, subtitled bio-molecular complexity inspired chemistry, combines the section that was devoted previously to lipid-inspired organic chemistry with systems chemistry. The re-arrangement of these two sections is based on the fact that most of the lipid-inspired chemistry reported deals with the study of the behaviour of multi-component chemical systems, i.e. species in solution and species attached to the membrane. In general terms, therefore, this section is devoted to organic chemistry inspired by the complexity of biomolecular systems. In addition to the lipid-membrane inspired organic chemistry, the last section reports advances in the study of self-sorting mixtures, dynamic combinatorial chemistry and chemistry inspired by pre-biotic systems. Although not necessarily explicit, the study of emergent properties of multi-component systems has become implicit in the development of many aspects of chemistry, including (or rather especially) bio-inspired organic chemistry.

Back cover (415-416).