In this review, particular attention will be given to the synthesis of organoboron compounds via the metal-catalyzed addition and coupling reactions, and their synthetic applications in organic syntheses. The traditional methods for the synthesis of organoboron compounds are based on the reaction of trialkyl borates with Grignard or lithium reagents (transmetalation) or the addition of H-B reagents to alkenes or alkynes (uncatalyzed hydroboration). Although these methods are now most common and convenient for large-scale preparations, the metal-catalyzed reactions are advantageous in terms of efficiency and selectivity of the transformations. Hydroboration of alkenes and alkynes is one of the most studied of reactions in the synthesis of organoboron compounds and their application to organic synthesis. However, the catalyzed hydroboration to be a more interesting strategy to realize the different chemo-, regio-, diastereo-, and enantioselectivities, relative to the uncatalyzed reaction. The cross-coupling reaction of metal-boryl reagents is an alternative to the transmetalation method and perhaps a more convenient and direct protocol for the synthesis of organoboron compounds from organic halides and aromatic C-H bond. Much attention has been recently focused on organoboronic acids and their esters due to their practical usefulness for synthetic organic reactions including asymmetric synthesis, combinatorial synthesis, and polymer synthesis, molecular recognition such as host-guest compounds, and neutron capture therapy in treatment of malignant melanoma and brain tumor. New synthetic procedures reviewed in this article will serve to find further applications of organoboron compounds.
A new concept in the design of a unique device for green oxidation was demonstrated by using a temperature responsive polymer support, poly (N-isopropylacrylamide) (PNIPAAm). The PNIPAAm-based oxidation catalysts were synthesized, whose affinity for organic substrate in water could be controlled by external temperature change. Application of this intelligence to provide novel catalytic oxidation systems brought a remarkable acceleration of the reactivity and an ease of catalyst recovering in the oxidation with hydrogen peroxide, tert-butyl hydroperoxide, and oxygen gas (O2). In addition, the recovered catalyst could also be used for consecutive reactions without any significant loss of its catalytic efficacy.
Fluorinated organic compounds have received considerable attention because they possess unique properties such as greater stability, higher lipophilicity, high electronegativity, and water and oil repellency, which are potentially beneficial in terms of development of novel pharmaceuticals and advanced materials. Such extreme and bizarre behaviors of the fluoro-organic compounds however, often make the synthesis of them all the more complicated, especially, when the synthesis of target compounds requires an enantio-controlled methodology. Many strategies can be employed for introduction of asymmetry into organic molecules, the enantioselective fluorination and fluoromethylation reactions are especially attractive because non-fluorinated prochiral substrates can be directly transformed to chiral fluoro-organic compounds with controlled absolute configuration. Significant progress has been made in the development of asymmetric fluorination reactions in recent years; however, the direct enantioselective trifluoromethylation remains achallenge. In this article, we review the recent developments in the enantioselective trifluoromethylation reactions including nucleophilic, electrophillic and radical approaches. Although the emphasis of this report will be on the enantioselective trifluoromethylation reaction, as well as the less studied enantioselective difluoromethylation and monofluoromethylation reactions will also be covered.
This review article focuses on the self-assembly of amphiphilic molecules into discrete, hollow cylindrical tubular architectures (organic nanotubes). Researches on the nanotube formation from dumbbell-shaped peptide lipids, 1-O-glucopyranoside and 1-N-glucopyranosylamide lipids, and wedge-shaped bolaamphiphiles with carboxylic, amino, and oligoglycine groups at one end have been outlined with their characteristic self-assembly. Finally, recent progress on massive production, dimension control, and novel functions of organic nanotubes are described.
Semiconductor nanoclusters and nanoparticles of cadmium chalcogenides have attracted special attention due to their unique optical properties. We particularly take notice of the host-guest chemistry and molecular events at the surface of small clusters and have been exploring unique functions by designing the organic environment around the cluster. In this article we review our recent approaches utilizing molecular clusters with a general formula Cd10S16R12 having twelve surface organic groups. Aryl-substituted clusters trapped ammonium cations among the surface aromatics through cation-π interaction, and such an intercalative cation binding caused a notable enhancement of the cluster photoluminescence at -600 nm. A systematic study using a series of substituted-phenyl-capped clusters revealed that the electronic properties of the substituents on the phenyl rings notably affect the cation binding capability as well as the photoluminescence emission energy. It was also found that the cation intercalation promotes the formation ofπ-stacked dimer of the aromatic moiety on the cluster surface. Highly sensitive and selective turn-on photoluminescence response to Cu (I) and Ag(I) in neutral buffer was also achieved by using an oligo(ethyleneglycol)-modified aryl-substituted cluster.
Friedel-Crafts reaction is a classical and fundamental reaction and powerful tool to make a carbon-carbon bond on a variety of aromatic ring such as phenol, aniline, pyrrole, and indole. A recent advance of the asymmetric version using chiral metal and non-metal catalysts is significant. This mini-review focuses on the most up-to date results.
Specific conversion of C-X bond to C-C bond by palladium-catalyzed reaction has been widely used in organic synthesis. Recently, several groups reported unusual C-C bond formation occurred at a different carbon from which halogen was initially attached. These reaction has been considered to happen through intramolecular migration of palladium before the C-C bond was formed. Larock et al. discovered a set of reaction conditions which enables to switch such migration on or off. Sharp et al. reported stepwise migration of isolated complexes. By focusing on these results, intramolecular palladium migration will be briefly discussed.