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The idea of carbon–hydrogen functionalization, in which C–H bonds are modified at will, represents a paradigm shift in the standard logic of organic synthesis; here, dirhodium catalysts are used to achieve highly site-selective, diastereoselective and enantioselective C–H functionalization of n -alkanes and terminally substituted n -alkyl compounds. Functionalization of unactivated C–H bonds Organic synthesis has traditionally relied heavily on the introduction and manipulation of functional groups, such as carbon–oxygen or carbon–halogen bonds. Much current research is focused on a potentially powerful alternative strategy in which carbon–hydrogen bonds, normally much less reactive and therefore resistant to functionalization, are somehow persuaded to be more easily modified. These authors report that it is possible to selectively functionalize an unactivated C–H bond by the use of well-defined catalysts to control the site selectivity, without the need for a directing or anchoring group present in the molecule. They use dirhodium catalysts to achieve diastereoselective and enantioselective C–H functionalization of n -alkanes and terminally substituted n -alkyl compounds. The reactions proceed in high yield and can be carried out on substrates containing other functional groups such as halides, silanes, and esters. The laboratory synthesis of complex organic molecules relies heavily on the introduction and manipulation of functional groups, such as carbon–oxygen or carbon–halogen bonds; carbon–hydrogen bonds are far less reactive and harder to functionalize selectively. The idea of C–H functionalization, in which C–H bonds are modified at will instead of the functional groups, represents a paradigm shift in the standard logic of organic synthesis 1 , 2 , 3 . For this approach to be generally useful, effective strategies for site-selective C–H functionalization need to be developed. The most practical solutions to the site-selectivity problem rely on either intramolecular reactions 4 or the use of directing groups within the substrate 5 , 6 , 7 , 8 . A challenging, but potentially more flexible approach, would be to use catalyst control to determine which site in a particular substrate would be functionalized 9 , 10 , 11 . Here we describe the use of dirhodium catalysts to achieve highly site-selective, diastereoselective and enantioselective C–H functionalization of n -alkanes and terminally substituted n -alkyl compounds. The reactions proceed in high yield, and functional groups such as halides, silanes and esters are compatible with this chemistry. These studies demonstrate that high site selectivity is possible in C–H functionalization reactions without the need for a directing or anchoring group present in the molecule.

The functionalization of specific inert C–H bonds avoids the need for functional groups in organic synthesis and here the challenges of this approach are overcome using a dirhodium catalyst that is capable of C–H bond site-selectivity. Targeted tertiary C–H activation Carbon–hydrogen (C–H) bond functionalization has gained traction over recent years as a synthetically useful transformation, as it avoids the need for functional groups to do synthesis. These bonds are typically inert, and selectively reacting one in a molecule that is made up of mainly C–H bonds is a challenge. Here, Huw Davies and colleagues report that a dirhodium catalyst can selectively modify unactivated tertiary C–H bonds (that is, on a carbon with three carbon substituents) with generally high stereo- and site-selectivity. Moreover, several natural products were modified by this route, including steroids and a vitamin E derivative, indicating the use of this chemistry for the late-stage functionalization of complex molecules. The synthesis of complex organic compounds usually relies on controlling the reactions of the functional groups. In recent years, it has become possible to carry out reactions directly on the C–H bonds, previously considered to be unreactive 1 , 2 , 3 . One of the major challenges is to control the site-selectivity because most organic compounds have many similar C–H bonds. The most well developed procedures so far rely on the use of substrate control, in which the substrate has one inherently more reactive C–H bond 4 or contains a directing group 5 , 6 or the reaction is conducted intramolecularly 7 so that a specific C–H bond is favoured. A more versatile but more challenging approach is to use catalysts to control which site in the substrate is functionalized. p450 enzymes exhibit C–H oxidation site-selectivity, in which the enzyme scaffold causes a specific C–H bond to be functionalized by placing it close to the iron–oxo haem complex 8 . Several studies have aimed to emulate this enzymatic site-selectivity with designed transition-metal catalysts but it is difficult to achieve exceptionally high levels of site-selectivity 9 , 10 , 11 . Recently, we reported a dirhodium catalyst for the site-selective functionalization of the most accessible non-activated (that is, not next to a functional group) secondary C–H bonds by means of rhodium-carbene-induced C–H insertion 12 . Here we describe another dirhodium catalyst that has a very different reactivity profile. Instead of the secondary C–H bond 12 , the new catalyst is capable of precise site-selectivity at the most accessible tertiary C–H bonds. Using this catalyst, we modify several natural products, including steroids and a vitamin E derivative, indicating the applicability of this method of synthesis to the late-stage functionalization of complex molecules. These studies show it is possible to achieve site-selectivity at different positions within a substrate simply by selecting the appropriate catalyst. We hope that this work will inspire the design of even more sophisticated catalysts, such that catalyst-controlled C–H functionalization becomes a broadly applied strategy for the synthesis of complex molecules.

Carbon–hydrogen (C–H) bonds have long been considered unreactive and are inert to traditional chemical reagents, yet new methods for the transformation of these bonds are continually being developed 1 – 9 . However, it is challenging to achieve such transformations in a highly selective manner, especially if the C–H bonds are unactivated 10 or not adjacent to a directing group 11 – 13 . Catalyst-controlled site-selectivity—in which the inherent reactivities of the substrates 14 can be overcome by choosing an appropriate catalyst—is an appealing concept, and substantial effort has been made towards catalyst-controlled C–H functionalization 6 , 15 – 17 , in particular methylene C–H bond functionalization. However, although several new methods have targeted these bonds in cyclic alkanes, the selectivity has been relatively poor 18 – 20 . Here we illustrate an additional level of sophistication in catalyst-controlled C–H functionalization, whereby unactivated cyclohexane derivatives can be desymmetrized in a highly site- and stereoselective manner through donor/acceptor carbene insertion. These studies demonstrate the potential of catalyst-controlled site-selectivity to govern which C–H bond will react, which could enable new strategies for the production of fine chemicals. Unactivated cyclohexane derivatives can be desymmetrized by site- and stereoselective C–H functionalization using carbene-insertion chemistry.

The kagome lattice, composed of a planar array of corner-sharing triangles, is one of the most geometrically frustrated lattices. The realization of a spin S = 1/2 kagome lattice antiferromagnet is of particular interest because it may host an exotic form of matter, a quantum spin liquid state, which shows long-range entanglement and no magnetic ordering down to 0 K. A few S = 1/2 kagome lattice antiferromagnets exist, typically based on Cu2+, d9 compounds, though they feature structural imperfections. Herein, we present the synthesis of (CH3NH3)2NaTi3F12, which comprises an S = 1/2 kagome layer that exhibits only one crystallographically distinct Ti3+, d1 site, and one type of bridging fluoride. A static positional disorder is proposed for the interlayer CH3NH3+. No structural phase transitions were observed from 1.8 K to 523 K. Despite its spin-freezing behaviour, other features—including its negative Curie–Weiss temperature and a lack of long-range ordering—imply that this compound is a highly frustrated magnet with unusual magnetic phase behaviours.The highly frustrated spin-1/2 kagome lattice antiferromagnet, predicted to exhibit unconventional magnetic behaviours, has remained difficult to synthesize without structural imperfections. Now, a d1-titanium fluoride kagome lattice antiferromagnet has been prepared in which there is only one crystallographically distinct Ti3+ site and one type of bridging fluoride, and it is shown to be a frustrated magnet with unusual magnetic properties.

Porous crystals made to order Controlling and predicting the structural properties of porous molecular crystals would have important implications in gas adsorption, separation and catalysis applications, but remain an unmet goal. This paper introduces a new concept of modular assembly at the molecular level for the formation of porous crystalline solids. Different large chiral molecules with intrinsic nanosize pores, or porous modules, self-assemble through chiral recognition during co-crystallization to produce solid porous frameworks. The three-dimensional structure of the final material can be predicted theoretically. The paper explores four different, albeit analogous, porous modules, which form four different porous solids. Nanoporous molecular frameworks 1 , 2 , 3 , 4 , 5 , 6 , 7 are important in applications such as separation, storage and catalysis. Empirical rules exist for their assembly but it is still challenging to place and segregate functionality in three-dimensional porous solids in a predictable way. Indeed, recent studies of mixed crystalline frameworks suggest a preference for the statistical distribution of functionalities throughout the pores 7 rather than, for example, the functional group localization found in the reactive sites of enzymes 8 . This is a potential limitation for ‘one-pot’ chemical syntheses of porous frameworks from simple starting materials. An alternative strategy is to prepare porous solids from synthetically preorganized molecular pores 9 , 10 , 11 , 12 , 13 , 14 , 15 . In principle, functional organic pore modules could be covalently prefabricated and then assembled to produce materials with specific properties. However, this vision of mix-and-match assembly is far from being realized, not least because of the challenge in reliably predicting three-dimensional structures for molecular crystals, which lack the strong directional bonding found in networks. Here we show that highly porous crystalline solids can be produced by mixing different organic cage modules that self-assemble by means of chiral recognition. The structures of the resulting materials can be predicted computationally 16 , 17 , allowing in silico materials design strategies 18 . The constituent pore modules are synthesized in high yields on gram scales in a one-step reaction. Assembly of the porous co-crystals is as simple as combining the modules in solution and removing the solvent. In some cases, the chiral recognition between modules can be exploited to produce porous organic nanoparticles. We show that the method is valid for four different cage modules and can in principle be generalized in a computationally predictable manner based on a lock-and-key assembly between modules.

The research on chiral recognition and chiral selection is not only fundamental in resolving the puzzle of homochirality, but also instructive in chiral separation and stereoselective catalysis. Here we report the chiral recognition and chiral selection during the self-assembly process of two enantiomeric wheel-shaped macroanions, [Fe 28 ( μ 3 -O) 8 (Tart) 16 (HCOO) 24 ] 20− (Tart= D - or L -tartaric acid tetra-anion). The enantiomers are observed to remain self-sorted and self-assemble into their individual assemblies in their racemic mixture solution. The addition of chiral co-anions can selectively suppress the self-assembly process of the enantiomeric macroanions, which is further used to separate the two enantiomers from their mixtures on the basis of the size difference between the monomers and the assemblies. We believe that delicate long-range electrostatic interactions could be responsible for such high-level chiral recognition and selection. Certain chiral macroions have previously been shown to self-assemble into spherical structures. Here, the authors observe self-sorting of racemic macroions into enantiomeric ‘blackberry’-shaped structures, and furthermore show that the addition of chiral co-anions allows the formation of a single enantiomer.

1,3-Dimethyl-2,3-dihydrobenzo[ d ]imidazoles, 1H , and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[ d ]imidazoles, 1 2 , are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[ d ]imidazolium ( 1g–i + , respectively) have been synthesized and reduced with NaBH 4 to 1gH , 1hH , and 1iH , and with Na:Hg to 1g 2 and 1h 2 . Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- ( 1b + ) and 2-cyclohexylbenzo[ d ]imidazolium ( 1e + ) salts. E ( 1 + / 1 • ) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducing E ( 1 + / 1 • ) values, as well as cathodic shifts in E ( 1 2 •+ / 1 2 ) and E ( 1H •+ / 1H ) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the 1H species with PC 61 BM. Because 2-aryl groups stabilize radicals, 1b 2 and 1g 2 exhibit weaker bonds than 1e 2 and 1h 2 and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene ( VII ) via a “cleavage-first” pathway, while 1e 2 and 1h 2 react only via “electron-transfer-first”. 1h 2 exhibits the most cathodic E ( 1 2 •+ / 1 2 ) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers with VII via “electron-transfer-first”. Crystal structures show rather long central C–C bonds for 1b 2 (1.5899(11) and 1.6194(8) Å) and 1h 2 (1.6299(13) Å).

The natural compound Genkwanin (systematic name: 5-hydroxy-2-(4-hydroxyphenyl)-7-methoxychromen-4-one) C16H12O5 (1) is a non-glycosylated flavonoid isolated from Callicarpa americana. Microcrystals of Genkwanin were prepared by slow evaporation of a methanol solution under low temperature conditions. The structure of 1 was determined based on spectroscopic analyses, one-dimensional NMR, HRESIMS and was confirmed by single-crystal X-ray diffraction. The crystals grow as very thin needles with an extremely high aspect ratio and with the long axis (along the y-axis) corresponding to the very short unit cell b-axis. There are two independent molecules in the asymmetric unit with two different conformations and modes of packing in the crystal. One molecule has a higher degree on non-planarity than the other. The short stacking distance and separation between the molecules implies a high degree of co-planarity consistent with a conjugated system. The crystal structure is non-centrosymmetric but achiral.

The discovery and study of novel bacterial species offer an opportunity to identify new microbial biological processes, molecular mechanisms, and secondary metabolites, such as new antibiotics. Our work indicates that slow-growing organisms inhabiting nutrient-limited environments may represent an enriched source of novel microbial species. Furthermore, we find that a subset of these organisms is likely to produce corresponding novel antimicrobials, presumably as a means to outcompete faster-growing rival organisms. Indeed, we show that a putative new Streptomyces species is capable of producing a previously undescribed antimicrobial, pyocyanin A, with potent, selective antibacterial toward Acinetobacter baumannii , a prominent cause of antibiotic-resistant infections.

X-ray crystallographic and theoretical charge-density data for a series of compounds—[(Co(Ts3tren))M(Co(Ts3tren))], (M = Mg, Ca, Sr and Ba)—were examined. The crystal structures were isostructural, and the alkaline-earth-metal ions had the same six-coordinate environment oxygen donor atoms which was octahedral despite the large variation in their ionic radii. The isomorphism of these molecules was surprising, and a theoretical examination of their electronic structures, with various metal ions along the series, provided detailed insight into their stabilities. The theoretical and experimental data were consistent and agreed well. The local properties of the Co(II) ion and its donor atoms were relatively independent of the alkaline earth metals.