Annual Reports Section "B" (Organic Chemistry) (v.108, #00)
Front cover (1-2).
Contents list (3-10).
Introduction by Phil Page; Ian Cunningham, Scientific Editors (11-14).
Synthetic methods Part (i) Free-radical reactions by Gareth J. Rowlands (15-28).
Two topics dominate this year's review; the use of metals in radical transformations and photoredox catalysis for the generation of alkyl radicals. In the former category, the use of potassium tert-butoxide in conjunction with a diamine ligand as a means of forming aryl radicals has the potential for the greatest impact. The use of photoredox catalysis as a mild method of initiating radical reactions appears to have opened a new vista in free-radical chemistry. One of the more exciting advances in this area is the use of a simple organic dye instead of the more common ruthenium complexes.
Synthetic methods Part (ii) oxidation and reduction methods by James K. Howard; Christopher J. T. Hyland (29-52).
This Report highlights key advances in some of the most commonly used oxidation and reduction reactions, focusing on the literature from 2011. The structure of this review follows that of the previous years Report by Asghar and Lewis. (S. F. Asghar and S. E. Lewis, Annu. Rep. Prog. Chem., Sect. B, 2011, 107, 34, ref 1). In the field of oxidation, a number of prominent advances have emerged. Notably, Shi and co-workers continue to build on their work in the deamination field through their detailed studies on the regioselectivity of the Cu(i)-catalysed deamination of conjugated dienes (Y. Shi et al. J. Am. Chem. Soc., 2011, ref 36). They reveal that the regioselectivity is governed by the the choice of Cu(i) catalyst and the substituents on the diene substrate. There have also been significant advances in the area of C–H oxidation, with Stambuli showing the stereoselectivity of cis-vinylsilane allylic acetoxylation to be dependent upon the nature of the oxidant used (Stambuli et al. J. Am. Chem. Soc., 2011, ref 66). In the field of reduction chemistry, the Ward group developed an artificial metalloenzyme, where an iridium-catalyst was incorporated into a chiral enzyme for the asymmetric transfer of hydrogen for the production of enantiopure amines (Ward et al. Angew. Chem. Int. Ed., 2011, ref 129). Meanwhile, Strotman and co-authors have demonstrated the first intramolecular reductive amination between dialkyl ketones and aliphatic amines. (Strotman et al. J. Am. Chem. Soc., 2011, ref 121).
Heteroatom methods by Daniel Best; Alan R. Burns; Graham Pattison; Hon Wai Lam (53-70).
This report presents a personal selection of advances in organoheteroatom chemistry reported in 2011.
Organometallic chemistry by Etienne Baranoff; John S. Fossey (71-97).
Highlights from the organometallic literature appearing in 2011 are surveyed. Selected reports are compiled, uses of organometallic species as drugs, organometallic compounds in synthesis and particular but not exclusive attention is paid to the areas of organometallics for solar and electronics applications.
Organocatalysis by Benjamin R. Buckley; Marc C. Kimber; Natasha H. Slater (98-109).
Reactions carried out with substoichiometric quantities of organic molecules as catalysts have received much attention over the past decade. This review highlights progress in 2011 towards highly enantioselective organocatalytic systems and the natural product/biologically active compounds that can be prepared using these types of processes.
Heterocyclic chemistry by Fawaz Aldabbagh (110-130).
The main modes of heterocyclic-ring synthesis in 2011 were cycloadditions, cyclizations, multi-component reactions, and ring-expansions with copper(i), gold(i), iron, palladium and rhodium being the most widely used transition metal catalysts. Some syntheses achieve good regioselectivity (e.g. organocatalysis) without transition metals.
Marine natural products by Robert A. Hill (131-146).
This review covers the literature on marine natural products published in 2011. 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, meroterpenoids, alkaloids and peptides.
Highlight syntheses by Nadale K. Downer-Riley; Yvette A. Jackson (147-170).
This review provides a sample of the total syntheses of both structurally complex and popular natural products reported in the chemical literature in 2011.
Supramolecular chemistry by Jian Tian (171-185).
The year 2011 has seen many significant developments in supramolecular chemistry. This report presents a personal selection of advances that have made by various research groups. In line with previous articles from this series, the report is subdivided into three broad sections covering molecular recognition, structure and assembly, and functional systems.
Supramolecular chemistry of donor–acceptor interactions by Koujiro Tambara; G. Dan Pantoş (186-201).
This report highlights some of the advances that have been made in the study of donor–acceptor interactions and their applications in the construction of functional supramolecular architectures in 2011. The review is organised into three broad sections encompassing light-harvesting systems, mechanically interlocked molecules and donor–acceptor chromophores.
Biotransformations by Gideon Grogan (202-227).
This report reviews significant developments in applications of biological catalysis in synthetic organic chemistry for the year 2011. In the area of hydrolase-catalysed biotransformations, lipases have been used in dynamic kinetic resolutions of amines at low-temperature using radical-based racemisation methods. A system has also been developed for the lipase catalysed desymmetrisation of allenic diols. An unusual promiscuous activity of formate dehydrogenase has been described in which the enzyme catalysed a hydrolytic reaction. In reductase biotransformations, ene reductases of the Old Yellow Enzyme family have been applied to the asymmetric reduction of Baylis-Hillman adducts and also shown, in some cases, to catalyse oxazete formation in the transformation of nitro-alkenes. The carbon–carbon bond forming enzyme benzaldehyde lyase was reported to catalyse N-hydroxamic acid formation from benzaldehydes and nitrosobenzenes. An (R)-selective arylmalonate decarboxylase has been engineered either to act as a racemase or to catalyse decarooxylation with inverted enantioselectivity. New developments in oxidase biocatalysis include the application of flavin-dependent Bereberine Bridge Enzyme to the resolution of reticuline-like substrates through carbon–carbon bond formation. A Baeyer-Villiger monooxygenase catalysed a dynamic kinetic resolution using racemic substrates susceptible to racemisation at alkaline pH. Cytochromes P450 have been applied to the oxidation of gaseous alkanes including methane, in the presence of perfluoro alkanoic acids. The peroxygenase AaeAPO has been used to catalyse hydroxylation and epoxidation reactions in photobiocatalytic systems. Finally, artificial metalloenzymes based on the streptavidin-biotin system have now been applied to asymmetric imine reduction, dihydroxylation and alkene metathesis.
Reaction mechanisms: radical and radical ion reactions by Uta Wille (228-250).
Radicals and radical ions are involved as intermediates in numerous chemical processes that range from synthesis to reactions in biological systems. Knowledge of the mechanisms by which these different reactions proceed is therefore not only of fundamental importance for the development of new synthetic procedures, but is also crucial for the understanding of, for example, adverse effects of radical induced damage on human health. In the first part an overview on recent developments in synthetic radical chemistry will be given with special emphasis on oxidative and reductive processes under metal and metal-free conditions. Advances in the mechanistic understanding of radical reactions in biological systems will be described in the second part.
Reaction mechanisms: pericyclic reactions by Edyta M. Greer; Christopher V. Cosgriff (251-271).
This review summarizes a number of articles published in 2011 describing mechanisms of pericyclic reactions. The types of reactions studied were of the cycloaddition sort (e.g., [2+1], [2+2], [3+2], [4+2], etc.), as well as sigmatropic (e.g., [1,2], [1,3], [3,3] shifts, etc.), group transfer (e.g., ene), and electrocyclic types. Interestingly, the literature on pericyclic cascade reactions was quite rich in 2011.
Reaction mechanisms: polar reactions by Hon Man Yau; Anna K. Croft (272-291).
This report highlights mechanistic work pertaining to polar reactions published in 2011. A range of topics is covered, spanning many different fields in chemistry, and as is often the case with much mechanistic work, the specific details of the work may span a number of the headings used to divide up this review. As such these headings should be used as guidelines. Areas such as supramolecular chemistry, biological systems and model systems, and solvent interactions are all featured.
Physical methods and techniques NMR spectroscopy by Mark Edgar (292-315).
NMR spectroscopy continues to evolve, with publications in 2011 providing an eclectic collection of applications, advances and incremental improvements. Publications highlights include: DNP in liquids and solids, decoupling effects at high spinning speed in solid-state, results from the 80 kHz spinning-speed 1 mm MAS rotor, enhanced diffusion methods, results from the new 1.0 GHz magnet, an intent to create a 1.3 GHz magnet, results from the 2.6 GHz pulsed-magnet, a cryogen-free MRI, and the use of multiple receivers to acquire multiple experiments within the same pulse sequence. 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 (316-333).
This report reviews the 2011 literature on reactivity in organised assemblies in aqueous systems. The basic scope of the report is broadly as before, and this year’s themes are as follows: (1) reactivity in micelles, including medium effects and compartmentalisation, micelle-assisted catalysis and functionalised amphiphiles, (2) DNA-based approaches to influencing reactivity, including DNA-templated reactions and DNA-based catalysis, and (3) nanoparticle-based assemblies for use in catalysis, including modulation of nanoparticle catalysis through thermoresponsive polymer shells and nanoparticle-supported catalysts.
Computational organic chemistry by Steven M. Bachrach (334-352).
This review highlights achievements in computational organic chemistry in 2011, including (1) identification of tunneling control, (2) examples of non-statistical dynamic effects in simple organic reactions, (3) use of computed NMR and optical spectra to aid in structure identification, and (4) a re-evaluation of the electrophilic aromatic substitution reaction.
Asymmetric catalysis by Enda Bergin (353-371).
This report covers advances in asymmetric catalysis in 2011. Due to the large subject area it is not possible to give adequate coverage to the entire field, but rather focus is given to the growing area of asymmetric catalysis with selected non-precious metals (namely iron, cobalt and copper).
Back cover (373-374).