Chemistry – An Asian Journal

Professor Eiichi Nakamura celebrates his 60th (Kan Reki) birthday this month. Professor Nakamura has had a far-reaching influence in multiple areas of chemistry through his outstanding contributions and is highly respected the world over. He was also extremely active in the founding of Chemistry—An Asian Journal, first serving on our Editorial Board and currently on our International Advisory Board. His enthusiasm and hard work were instrumental in the journal's success, and he has continued to set a high standard with his own publications in the journal. As a part of his birthday celebration, and as a tribute to Professor Nakamura's illustrious career, this special issue is in honor of this occasion. Cover picture courtesy of Mr. Shuzaburo Shibi, photographer: Mr. Masakatsu Shibata.

Ceci n'est pas un nez The above picture invites a free association (Margittesque) with the first synthetic sensor that mimics biological olfactory systems in lipid bilayer membranes. Dynamic polyion–counterion transporters are used as artificial olfactory receptors to generate multidimensional patterns. In their Full Paper on page 681 ff., J. Montenegro and S. Matile describe how complete charge inversion in the polyion–counterion complexes affords facile discrimination between, for example, enantiomers, cis/trans isomers, and homologues.

A Soft Target! Starting from the world of serendipity, molecular gel chemistry is now being transformed towards the programmed development of smart functions by utilizing the principles of supramolecular interaction. This Focus Review is an attempt to reveal the underlying correlation between the gel structure and function.

Efficient insertion: Early-transition-metal complexes bearing phenoxy–imine-type ligands can achieve selective and nonselective ethylene oligomerization with high efficiency. These complexes will be a rich source for the development of new ethylene-insertion catalysts.

Spacer Oddity: Hybrid azoles support a myriad of coordination polymers by serving as flexible and adaptable spacers through a range of coordination modes.

Diene Hard with a Vengeance: The scope and application of the 1,4-diiodo-1,3-dienes in organic synthesis is discussed, including their uses in assembling complex organic molecules, in the preparation of natural products, and in compounds potentially important for material science. Their key advantages include easy preparation from alkynes, high reactivity, excellent selectivity, and mild reaction conditions.

Go nano! The fabrication of layered nanomaterials, such as inorganic–inorganic, organic–inorganic, and bioinorganic nanohybrids (see picture), has been demonstrated through controlled lattice engineering techniques, including intercalation, exfoliation–reassembling, and pillaring reactions.

Small but deadly? As nanomaterial-based products enter the market, there is an urgent need for related research in order to prevent dramatic consequences of any health-oriented issues caused by nanotechnology-driven products. The results of research on nanotoxicity have profound significance because the design of nanomaterials used in industry and consumer products should be based on the outcome of such research. The research has multi-billion dollar significance for industry and an even greater value for consumers and health care.

The photophysical and electrochemical properties, as well as the intermolecular interactions of oligothiophenes, which incorporate the rigid, fused-ring bulky EMind groups, siginificantly depend on the number and location of the bulky EMind groups.

An umpoled method for regioselective functionalization of biaryls is demonstrated. As a model substrate, binol was converted into a tethered ortho-quinol derivative, allowing selective installation of nucleophiles at the C4 or C3 position to give monofunctionalized binol derivatives with complete retention of the axial stereochemistry.

An aldimine bearing a 3-methyl-2-pyridyl group undergoes [2+2+2] cycloaddition reaction with two alkyne molecules under nickel catalysis to afford a 1,2-dihydropyridine derivative in moderate to good yield. The reaction is likely to involve oxidative cyclization of the imine and alkyne, insertion of another alkyne, and CN reductive elimination, followed by a 1,5-sigmatropic hydrogen shift. The pyridyl group is proposed to facilitate the reaction by chelation to the aza-nickelacycle intermediates.

Micropatterns of cells were generated on a cyclic olefin copolymer (COC) by a combination of aryl-azide-based photopatterning of a polymerization initiator and surface-initiated atom-transfer radical polymerization of non-biofouling 3-(methacryloylamino)propyl)-dimethyl(3-sulfopropyl)ammonium hydroxide (MPDSAH). The optical transparency of the COC made it possible to generate the patterns indirectly through a COC slab.

Mesogenie in a bottle: The first liquid-crystalline 1,10-phenanthroline-based macrocycles were synthesized by Suzuki–Miyaura cross-coupling. Their optical properties and mesomorphism were investigated by UV/Vis absorption and emission spectroscopy, DSC, and 2D WAXS measurements. These studies revealed formation of columnar superstructures.

The planet of the azepines: Epoxy-fused azepines have been synthesized in a highly selective reaction with hemiaminals and vinyl sulfonium salts. Stereochemistry is controlled by the substituent at the four- or five-position of the hemiaminal. The key step involves ring-opening of the hemiaminal, conjugate addition onto a vinyl sulfonium salt, and epoxidation of the aldehyde by the in situ formed sulfur ylide.

The world on a plate: In addition to their role as a capping agent that selectively binds to the {111} faces of silver, the carboxylate group can coordinate with Ag⁺ ions to form complexes and thus substantially reduce the reduction rate of Ag⁺ ions, leading to the formation of silver seeds with both twin planes and stacking faults.

Huey Lewis (acid) and the News: Crystallographic and computational studies on the cationic-oxazaborolidine-catalyzed Diels–Alder reaction of acetylenic ketones indicated that the reaction proceeds through a favored syn, exo transition state. These results provide a basis for understanding why acyclic dienes give higher enantioselectivities than cyclic dienes.

We're bringing sexy back: The highly efficient introduction of stereogenic centers bearing methyl group by conjugate addition of RMgBr to α,β-unsaturated esters has been employed in the total syntheses of two sex pheromones (see scheme). Binap=[1,1′-binaphthalene]-2,2′-diylbis(diphenylphosphane).

Non-metallocene allyl complexes of early lanthanides (lanthanum, cerium, neodymium, and samarium), that contain a sulfur-linked bis(phenolate) ligand, catalyze the regioselective hydrosilylation of styrene.

From simplicity to complexity and diversity: This paper reports a synergistic strategy combining the Diels–Alder reaction, the ene reaction, and the allylation reaction all in one pot to construct important polycyclic scaffolds.

Switching off the best: The addition of TCNE and TCNQ to triple bonds is promoted by donor substitution of the acetylenic substrates. This study investigates the activation strength of different donors in this transformation. Selective switching-off of the strong anilino donor by protonation forces the cycloaddition-retro-electrocyclization of TCNE to the triple bond adjacent to the weaker ferrocenyl donor to form the usually unfavorable product.

CAACs are not NHCs! (NHC)CuH cannot be stored at room temperature, whereas a (CAAC)CuH is stable for weeks both in solution and in the solid state. In the presence of an additional L ligand, the hydride migrates to the carbene carbon, thus affording (CAAC,H)CuL complexes. CAAC=cyclic (alkyl)(amino)carbene; NHC=N-heterocyclic carbene.

An eye furan eye: A simple and efficient protocol for the synthesis of benzofuran and naphthofuran derivatives catalyzed by indium triflate was developed by coupling α,β-unsaturated nitroalkenes with phenol/naphthols. The present method provides arenofuran derivatives in one pot from readily available starting materials (DCE=1,2-dichloroethane; see scheme).

On neutral territory: A neutral palladium(II)-dimer catalyst system incorporating anionic sulfonamidoquinoline ligands is effective for the γ-selective and stereospecific allyl–aryl coupling between acyclic (E)-allylic acetates and arylboronic acids.

In the ring: The Michael-type cycloaddition of C₆₀ with (S,S)-diphenylsulfilimines (see scheme) was carried out to regioselectively afford bis- and tris-aziridinated fullerenes. The aziridination occurred exclusively at the same six-membered ring on C₆₀ to give a sole isomer. Their structures were determined by spectroscopic and single-crystal X-ray analyses.

Phthalocyanine on the beat: The formation of pseduohexagonal and linear patterns of copper phthalocyanine (CuPc) on a highly oriented pyrolytic graphite surface has been achieved (see picture) by co-adsorbing with 2,3,7,8,12,13-hexahexyloxy-truxenone (TrO23) at the solid/liquid interface. Analysis of high-resolution scanning tunneling microscopy images reveals the structural details of the arrangement of TrO23 and CuPc in the binary assembly structures.

The Discovery channel: The excited state intraligand charge transfer (ILCT) modulated fluorescence response of bipyridyl-based fluorophore against various chemical inputs is shown on filter paper using a microfluidic technique (see picture). The three different emission outputs generated from allow five different Boolean logic operations in independent and integrated modes.

Tubethumping: Selective dispersion of single-walled carbon nanotubes (SWCNTs) in order to preferentially solubilize distinct diameters or even chiralities can be considered as the definitive sorting tool. The enrichment of SWCNTs with diameters larger than 0.8 nm by a novel tweezer-type dispersant with perylene bis(imide) moieties as SWCNT anchor groups is presented.

Sum of the living: Hybrid block copolymers composed of poly(meth)acrylates and poly(vinyl ether)s are synthesized by in situ selective polymer end-transfer reactions. Organotellurium compounds are common chain-transfer agents for both living radical and living cationic polymerization reactions.

Lock, stock, and β barrel: β-Barrel protein mimics of dual functionality have been developed through the self-assembly of β-sheet-forming peptides (see graphic). A unique feature of this system is the formation of highly uniform and discrete water-soluble β-barrel nanoring structures highly similar to natural β-barrel proteins in structure and composition.

Frankenstein hybrids: A series of novel hybrids of three anticancer agents that share a common microtubule-stabilizing mode of action and tubulin binding site were designed and synthesized by a modular route with rational matching of structural components (see scheme).

As strong as an Aux: Chiral (R)-2-(isopropylsulfinyl)phenol (R=H) and preferably a more-electron-rich methoxy derivative (R=OCH₃) serve as auxiliaries for the asymmetric synthesis of chiral ruthenium/polypyridyl complexes.

It's not simple: According to theoretical and experimental studies, the formal [4+2] cycloaddition of dienynes proceeds by means of cyclopropyl gold(I) carbenes and not through simple carbocations (see scheme). The significance of homoallylic stabilization is shown, even for systems in which the tertiary carbocation is stabilized by two methyl groups.

Quick on the uptake: A piperazinephenyl-appended nucleoside (^PPU) was synthesized by a simple Suzuki-coupling reaction and incorporated into oligonucleotides for achieving enhancement of cellular uptakes. This building block (^PPU) is designed to have a cationic charge part and suitable fluorescence (see picture).

Out of orbit: A series of density functional theory (DFT) calculations on aliphatic and aromatic hydroxylation reactions have been performed by using [Fe^IVO(TMC)(L)]ⁿ⁺. These studies predict regioselective aliphatic hydroxylation over aromatic hydroxylation (see scheme). The observed trends and product distributions have been rationalized by using thermodynamic cycles and orbital assignments, and explain the reasons for the regioselectivity preference. (TMC=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, and L=CNCH₃ or Cl⁻).

The behavior of Sc₃N cluster inside the trifluoromethylated C₈₀ (I_h) fullerene cage was examined by structure elucidation of two new CF₃ derivatives, these are Sc₃N@C₈₀(CF₃)₁₄ and Sc₃N@C₈₀(CF₃)₁₆ (see picture; Sc red, N blue, C gray and violet, F green). The most significant structural features of Sc₃N@C₈₀(CF₃)_14,16 isomers are the multiple CF₃ additions to the THJ positions of the carbon cage and a high degree of Sc₃N ordering combined with large angular deviations from trigonal symmetry owing to Sc coordination to the cage.

Double activation: DFT calculations of the chiral-phosphoric-acid-catalyzed enantioselective Friedel–Crafts reaction of indoles with nitroalkenes were carried out. The reaction proceeds through the simultaneous activation of the indole and the nitroalkene on the Brønsted acidic (proton) and basic (phosphoryl oxygen) sites.

Animated amination: Functionalized heterocyclic zinc reagents are easily synthesized by a facile oxidative amination reaction of zinc amidocuprates prepared from various lithium amides (see scheme). For this purpose, PhI(OAc)₂ proved to be an efficient oxidant. Moreover, a new CN ring-closing reaction involving an oxidative amination step is reported.

Zinc-ing outside the box: Zinc–porphyrin-appended single-stranded polynorbornene and zinc–porphyrin-linked double-stranded polymeric ladderphane (see picture) have been used for complexation with 1,4-diazabicyclo[2.2.2]octane (DABCO) to generate an array of porphyrin–DABCO supramolecular scaffolds.

Amaresin grace: A highly convergent total synthesis of two proposed structures of maresin, a potent anti-inflammatory lipid mediator derived from docosahexaenoic acid (DHA), has been achieved. The four known fragments were assembled into maresin structures in 17 steps (see scheme). The two synthesized C7-diastereomers were found to be comparably active in blocking neutrophil infiltration in the acute peritonitis model.

Glowing gold! A series of gold(I) complexes with N-heterocyclic carbene, acetylide, and isocyanide ligands have been synthesized. At room temperature, most of these gold(I) complexes are emissive in the solid state and in solutions with emission lifetimes in the nanosecond to submicrosecond regime. Four complexes were found to aggregate into crystalline nanowires/nanobelts in freshly prepared THF/water dispersions.

Easy access to silacyclophanes: A new series of silacyclophanes, disilanyl double-pillared bisanthracenes (^SiDPBAs), was synthesized using a one-pot operation from 1,8-diiodoanthracenes. The major product with anti geometry bears a steplike structure favorable for σ–π conjugation, and the minor product with syn geometry bears a U-shaped structure favorable for excimer formation.

A benzyne-mediated one-pot indoline formation/cross-coupling sequence is used for the construction of a highly substituted common indole intermediate. The peripheral substituents were introduced using a Friedel–Crafts reaction on the indole intermediate in a modular fashion to complete the total synthesis.

Go total! A convergent route to galbulimima alkaloids is described. This route was successfully employed in the efficient syntheses of (−)-GB 13, (+)-GB 16, and (−)-himgaline.

Having a gas: The partial oxidation of methane over Pt/Al₂O₃ has been investigated by in situ Raman and pulse reaction methods. For the reaction at 700 °C with <1 ms contact time, pyrolysis of CH₄ on reduced platinum followed by coupling of two surface H atoms to H₂ and partial oxidation of surface carbon species to CO are the major reactions for synthesis gas formation in the oxidation zone (see graph).

A new rhodium-catalyzed reaction of fullerenes with organoboron compounds is described. This method enables introduction of various organic groups onto C₆₀ and C₇₀. The reaction generally proceeds with a high regioselectivity and in a mono-addition manner. Various functional fullerenes, such as fullerene-tagged amino acids and fullerene-capped π systems, can be synthesized.

Unfunctionalized trialkyl-substituted olefins are hydrogenated with high efficiency and excellent enantioselectivity using iridium complexes derived from chiral N,P ligands. In this way, pharmaceutically interesting and industrially relevant compounds with chiral alkyl fragments are easily accessible with high diastereo- and enantioselectivities.

SpringBoc reaction: An acid-catalyzed reaction of N-α-diazoacyl camphorsultams and N-Boc imines has been developed, as a facile means to provide trisubstituted aziridines in a highly stereoselective manner. The use of N-Boc α-ketimino esters and N-α-diazoacetyl camphorsultam as an alternative combination of substrates led to the construction of trisubstituted aziridines with two carbonyl functionalities (see scheme).

Saving the best for last: Enantioselective homoenolate additions have been hindered by the challenge of synthesizing N-mesityl-substituted azolium salts. A library of pyrrole-functionalized chiral triazolium salts was prepared by direct modification of the preformed azolium core.

Magnum PI: Gold-nanocluster catalysts, PI-Au, that were immobilized on polystyrene-based polymers with cross-linking moieties, were used to catalyze the syntheses of 1,2 and 1,3-diol monoesters and their derivatives from aldehydes. The effect of neighboring-group participation in the esterification reaction is also described.

Metall-o-Mix: A series of mixed-metallocene Group 4 metal chloride/amide/oxide/alkyl complexes bearing a CH₂-bridged ligand [H₂C(C₅Me₄)(C₂B₉H₁₀)]³⁻ have been prepared and structurally characterized. Their catalytic activity towards ethylene polymerization was examined.

A hard day's graft: NHS-ester-functionalized methallylsilanes showed remarkable grafting efficiencies with an acid catalyst. Mesoporous silica balls bearing covalently immobilized enzyme were obtained with high loading compared with conventional multistep grafting methods.

Stereoinduction: A thorough study on the diastereoselectivity in the TMM diyl mediated [2+3] cycloaddtion reaction of monosubstituted linear substrates to form angularly fused triquinanes was carried out. Substitution at position 3 provided complete diastereoselectivity, whilst positions 1 and 4 induced marginal stereoselectivity. Position 2 did not show any influence on the diastereoselectivity. Position 4 was incompatible with the cycloaddition reaction, as the carbene intermediate underwent OSi bond insertion to form a dihydrofuran ring.

This guest is bent on fitting in: Alkyltrimethylammonium and cucurbit[8]uril (CB[8]) form 1:1 host–guest complexes with a high binding constant (K≈10⁶ m⁻¹). A short hexyl chain can be fully encapsulated in an extended conformation inside the CB[8] cavity, whilst for longer aliphatic chains, from octyl to cetyl, the alkyl tails take on a U-shaped conformation inside the cavity, which follows the enthalpy–entropy compensation rule commonly observed in molecular recognition systems.

Salt-controlled reaction: The tandem aza-Michael reaction/enantioselective protonation of α-substituted α,β-unsaturated carbonyl compounds is described in detail. The combined use of chiral palladium complex 1 and amine salts was critical to obtain α-substituted β-amino carbonyl compounds with high enantioselectivity (see scheme).

Accelerated addition: Treatment of 2-vinylpyridine derivatives with styrylboronic acids under cobalt catalysis results in addition reactions. This represents a rare example of the cobalt-catalyzed reaction of organoboronic acids. Cobalt shows catalytic activity similar to rhodium, and catalyzes an unprecedented assembly of organoboronic acids and activated alkenes.

A library of chiral diphosphonite (bop) ligands was synthesized based on chiral hexasubstituted biphenols with fine-tuning capability. Their application for the synthesis of a key intermediate to indole alkaloids through a palladium-catalyzed intermolecular asymmetric allylic amination is reported (TBS=tert-butyldimethylsilyl, TIPS=triisopropylsilyl, dba=dibenzylideneacetone).

A sense of smell: Full charge inversion in the first synthetic system that operates, like biological olfactory systems, in lipid-bilayer membranes gives differential sensing systems with superior discriminatory power and responsiveness to gemini rather than octopus amphiphiles.

The copolymerization of vinylarenes with CO and the terpolymerization of vinylarene and polar vinyl monomers with CO have been achieved by using palladium phosphine-sulfonate catalysts.