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The first enantioselective carbometalation reaction of azabicycloalkenes has been achieved by iron catalysis to in situ form optically active organozinc intermediates, which are amenable to further synthetic elaborations. The observed chiral induction, along with the DFT and XAS analyses, reveals the direct coordination of the chiral phosphine ligand to the iron centre during the carbon–carbon and carbon–metal bond forming step. This new class of iron-catalysed asymmetric reaction will contribute to the synthesis and production of bioactive molecules.

We have developed novel surface plasmon resonance (SPR) sensor chips whose surfaces bear newly synthesized functional self-assembled monolayer (SAM) anchoring lignin through covalent chemical bonds. The SPR sensor chips are remarkably robust and suitable for repetitive and accurate measurement of noncovalent lignin–peptide interactions, which is of significant interest in the chemical or biochemical conversion of renewable woody biomass to valuable chemical feedstocks. The lignin-anchored SAMs were prepared for the first time by click chemistry based on an azide–alkyne Huisgen cycloaddition: mixed SAMs are fabricated on gold thin film using a mixture of alkynyl and methyl thioalkyloligo(ethylene oxide) disulfides and then reacted with azidated milled wood lignins to furnish the functional SAMs anchoring lignins covalently. The resulting SAMs were characterized using infrared reflection–absorption, Raman, and X-ray photoelectron spectroscopies to confirm covalent immobilization of the lignins to the SAMs via triazole linkages and also to reveal that the SAM formation induces a helical conformation of the ethylene oxide chains. Further, SPR measurements of the noncovalent lignin–peptide interactions using lignin-binding peptides have demonstrated high reproducibility and durability of the prepared lignin-anchored sensor chips.

We have developed a novel diastereoselective iron-catalyzed cross-coupling reaction of various glycosyl halides with aryl metal reagents for the efficient synthesis of aryl C-glycosides, which are of significant pharmaceutical interest due to their biological activities and resistance toward metabolic degradation. A variety of aryl, heteroaryl, and vinyl metal reagents can be cross-coupled with glycosyl halides in high yields in the presence of a well-defined iron complex, composed of iron(II) chloride and a bulky bisphosphine ligand, TMS-SciOPP. The chemoselective nature of the reaction allows the use of synthetically versatile acetyl-protected glycosyl donors and the incorporation of various functional groups on the aryl moieties, producing a diverse array of aryl C-glycosides, including Canagliflozin, an inhibitor of sodium-glucose cotransporter 2 (SGLT2), and a prevailing diabetes drug. The cross-coupling reaction proceeds via generation and stereoselective trapping of glycosyl radical intermediates, representing a rare example of highly stereoselective carbon-carbon bond formation based on iron catalysis. Radical probe experiments using 3,4,6-tri-O-acetyl-2-O-allyl-α-d-glucopyranosyl bromide (8) and 6-bromo-1-hexene (10) confirm the generation and intermediacy of the corresponding glycosyl radicals. Density functional theory (DFT) calculations reveal that the observed anomeric diastereoselectivity is attributable to the relative stability of the conformers of glycosyl radical intermediates. The present cross-coupling reaction demonstrates the potential of iron-catalyzed stereo- and chemoselective carbon-carbon bond formation in the synthesis of bioactive compounds of certain structural complexity.

A series of norvaline (Nva) peptides possessing ONO-pincer ruthenium complexes, Boc-{l-[Ru(pydc)(t-Bu-terpy)]Nva}n-OMe (n = 2–6), were synthesized successfully by solution-phase peptide synthesis. Efficient coupling of equimolar amounts of N-free Ru-bound norvaline peptides, H-{l-[Ru(pydc)(t-Bu-terpy)]Nva}n-OMe, and C-free Ru-bound norvaline, Boc-l-[Ru(pydc)(t-Bu-terpy)]Nva-OH, was achieved by using the 2-chloro-4,6-dimethoxy-1,3,5-triazine-based method. Structural analysis by means of CD and NMR spectroscopy revealed the formation of stable helical conformations in peptides more than three residues.

The self-assembled monolayer (SAM)-modified metallic nanoparticles (MNPs) often exhibit improved chemoselectivity in various catalytic reactions by controlling the reactants&rsquo, orientations adsorbed in the SAM, however, there have been a few examples showing that the reaction rate, i.e., catalytic activity, is enhanced by the SAM-modification of MNP catalysts. The critical parameters that affect the catalytic activity, such as the supports, nanoparticle size, and molecular structures of the SAM components, remain uninvestigated in these sporadic literature precedents. Here, we report the mechanistic investigation on the effects of those parameters on the catalytic activity of alkanethiolate SAM-functionalized gold nanoparticles (AuNPs) toward silane alcoholysis reactions. The evaluation of the catalytic reaction over two-dimensionally arrayed dodecanethiolate SAM-functionalized AuNPs with different supports revealed the electronic interactions between AuNPs and the supports contributing to the rate enhancement. Additionally, an unprecedented size effect appeared&mdash, the AuNP with a 20 nm radius showed higher catalytic activity than those at 10 and 40 nm. Infrared reflection&ndash, absorption spectroscopy revealed that the conformational change of alkyl chains of the SAM affects the entrapment of reactants and products inside the SAM, and therefore brings about the acceleration effect. These findings provide a guideline for further applying the SAM-functionalization technique to stereoselective organic transformations with designer MNP catalysts.

Two (ONO pincer)ruthenium‐complex‐bound norvalines, Boc−[Ru(pydc)(terpy)]Nva−OMe (1; Boc=tert‐butyloxycarbonyl, terpy=terpyridyl, Nva=norvaline) and Boc−[Ru(pydc)(tBu‐terpy)]Nva−OMe (5), were successfully synthesized and their molecular structures and absolute configurations were unequivocally determined by single‐crystal X‐ray diffraction. The robustness of the pincer Ru complexes and norvaline scaffolds against acidic/basic, oxidizing, and high‐temperature conditions enabled us to perform selective transformations of the N‐Boc and C−OMe termini into various functional groups, such as alkyl amide, alkyl urea, and polyether groups, without the loss of the Ru center or enantiomeric purity. The resulting dialkylated Ru‐bound norvaline, n‐C11H23CO−l‐[Ru(pydc)(terpy)]Nva−NH‐n‐C11H23 (l‐4) was found to have excellent self‐assembly properties in organic solvents, thereby affording the corresponding supramolecular gels. Ru‐bound norvaline l‐1 exhibited a higher catalytic activity for the oxidation of alcohols by H2O2 than parent complex [Ru(pydc)(terpy)] (11 a).

High-yielding cross-coupling reactions of various combinations of aryl chlorides and alkyl Grignard reagents have been developed by using an iron(III) fluoride/1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (SIPr) catalyst composite. The iron(III) fluoride/SIPr-catalyzed aryl–alkyl coupling demonstrates unprecedented scope for both aryl chlorides and alkyl Grignard reagents, thus enabling the first efficient coupling of electron-rich (deactivated) aryl chlorides with alkyl Grignard­ reagents without β-hydrogens. The present reaction is also effective for diverse alkyl Grignard reagents such as (trimethylsilyl)methyl, primary, and secondary alkyl Grignard reagents.

In the molecule of (2,7-dimethoxynaphthalen-1-yl)(3-fluorophenyl)methanone, C19H15FO3, (I), the dihedral angle between the plane of the naphthalene ring system and that of the benzene ring is 85.90 (5)°. The molecules exhibit axial chirality, with either anR- or anS-stereogenic axis. In the crystal structure, each enantiomer is stacked into a columnar structure and the columns are arranged alternately to form a stripe structure. A pair of (methoxy)C—H...F hydrogen bonds and π–π interactions between the benzene rings of the aroyl groups link anR- and anS-isomer to form a dimeric pair. These dimeric pairs are piled up in a columnar fashion through (benzene)C—H...O=C and (benzene)C—H...OCH3hydrogen bonds. The analogous 1-benzoylated compound, namely (2,7-dimethoxynaphthalen-1-yl)(phenyl)methanone [Katoet al.(2010).Acta Cryst.E66, o2659], (II), affords three independent molecules having slightly different dihedral angles between the benzene and naphthalene rings. The three independent molecules form separate columns and the three types of column are connected to each otherviatwo C—H...OCH3hydrogen bonds and one C—H...O=C hydrogen bond. Two of the three columns are formed by the same enantiomeric isomer, whereas the remaining column consists of the counterpart isomer. In the case of the fluorinated 1-benzoylated naphthalene analogue, namely (2,7-dimethoxynaphthalen-1-yl)(4-fluorophenyl)methanone [Watanabeet al.(2011).Acta Cryst.E67, o1466], (III), the molecular packing is similar to that of (I),i.e.it consists of stripes ofR- andS-enantiomeric columns. A pair of C—H...F hydrogen bonds betweenR- andS-isomers, and C—H...O=C hydrogen bonds betweenR(orS)-isomers, are also observed. Consequently, the stripe structure is apparently induced by the formation ofR...Sdimeric pairs stacked in a columnar fashion. The pair of C—H...F hydrogen bonds effectively stabilizes the dimeric pair ofR- andS-enantiomers. In addition, the co-existence of C—H...F and C—H...O=C hydrogen bonds makes possible the formation of a structure with just one independent molecule.

A PCP pincer palladium-complex-bound norvaline, Boc- l -[Pd]Nva-OMe, was synthesized and fully characterized by NMR, FT-ICR-MS, and X-ray crystallography. Selective N- and C-terminus transformations of Boc- l -[Pd]Nva-OMe were performed by conventional deprotection–condensation procedures to afford lipophilic palladium-bound norvaline derivatives without metal detachment. The N-/C-bisfunctionalized palladium-bound norvaline showed self-assembly properties, as evidenced by supramolecular gel formation. The catalytic activity of the supramolecular gel was assessed in the 1,4-conjugate addition of phenylboronic acid.

The NCN-pincer Pd-complex-bound norvalines Boc-D/L-[PdCl(dpb)]Nva-OMe (1) were synthesized in multigram quantities. The molecular structure and absolute configuration of 1 were unequivocally determined by single-crystal X-ray structure analysis. The robustness of 1 under acidic/basic conditions provides a wide range of N-/C-terminus convertibility based on the related synthetic transformations. Installation of a variety of functional groups into the N-/C-terminus of 1 was readily carried out through N-Boc- or C-methyl ester deprotection and subsequent condensations with carboxylic acids, R(1)COOH, or amines, R(2)NH2 , to give the corresponding N-/C-functionalized norvalines R(1)-D/L-[PdCl(dpb)]Nva-R(2) 2-9. The dipeptide bearing two Pd units 10 was successfully synthesized through the condensation of C-free 1 with N-free 1. The robustness of these Pd-bound norvalines was adequately demonstrated by the preservation of the optical purity and Pd unit during the synthetic transformations. The lipophilic Pd-bound norvalines L-2, Boc-L-[PdCl(dpb)]Nva-NH-n-C11H23, and L-4, n-C4H9CO-L-[PdCl(dpb)]Nva-NH-n-C11H23, self-assembled in aromatic solvents to afford supramolecular gels. The assembled structures in a thermodynamically stable single crystal of L-2 and kinetically stable supramolecular aggregates of L-2 were precisely elucidated by cryo-TEM, WAX, SAXS, UV/Vis, IR analyses, and single-crystal X-ray crystallography. An antiparallel β-sheet-type aggregate consisting of an infinite one-dimensional hydrogen-bonding network of amide groups and π-stacking of PdCl(dpb) moieties was observed in the supramolecular gel fiber of L-2, even though discrete dimers are assembled through hydrogen bonding in the thermodynamically stable single crystal of L-2. The disparate DSC profiles of the single crystal and xerogel of L-2 indicate different thermodynamics of the molecular assembly process.

The enhanced catalytic activity of ruthenium complex-bound norvaline Boc-L-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.

The enhanced catalytic activity of ruthenium complex-bound norvaline Boc-L-[Ru]Nva-OMe 1, in which the ONO-pincer ruthenium complex Ru(pydc)(terpy) 2 is tethered to the α-side chain of norvaline, has been demonstrated for the oxidation of methoxybenzenes to p-benzoquinones with a wide scope of substrates and unique chemoselectivity.

offering a practical alternative to conventional nickel- and palladium-catalyzed aryl-alkyl couplings

In this research, we report the development, characterization and application of various plasmonic substrates (with localized surface plasmon resonance wavelength tunable by gold nanoparticle size) for two-photon absorption (TPA)-induced photodimerization of an anthracene derivative, anthracene carboxylic acid, in both surface and solution phase under incoherent visible light irradiation. Despite the efficient photoreaction property of anthracene derivatives and the huge number of publications about them, there has never been a report of a multiphoton photoreaction involving an anthracene derivative with the exception of a reverse photoconversion of anthracene photodimer to monomer with three-photon absorption. We examined the progress of the TPA-induced photoreaction by means of surface-enhanced Raman scattering, taking advantage of the ability of our plasmonic substrate to enhance and localize both incident light for photoreaction and Raman scattering signal for analysis of photoreaction products. The TPA-induced photoreaction in the case of anthracene carboxylic acid coated 2D array of gold nanoparticles gave different results according to the properties of the plasmonic substrate, such as the size of the gold nanoparticle and also its resultant optical properties. In particular, a stringent requirement to achieve TPA-induced photodimerization was found to be the matching between irradiation wavelength, localized surface plasmon resonance of the 2D array, and twice the wavelength of the molecular excitation of the target material (in this case, anthracene carboxylic acid). These results will be useful for the future development of efficient plasmonic substrates for TPA-induced photoreactions with various materials.

The dimerization reactions of 2-bromo-3,5,6-trimethyl-1,4-benzoquinone have been examined. 2,2′-Dimeric benzoquinone was prepared via a Stille-type homocoupling, whereas an oxepin was formed by the...

An NCN-pincer Pd-complex-bound norvaline-based supramolecular gel showed efficient catalytic activities for the intramolecular addition–cyclization of alkynoic acid and phenol derivatives in water ...

Novel NCN-pincer Pd-complex-bound norvaline derivatives were synthesized. The N- and C-termini-alkylated Pd–norvalines spontaneously assemble into fibrous aggregates to form supramolecular gels, in...

The title molecule, C44H30O8, lies about a crystallographic inversion centre located at the centre of the central benzene ring. The benzene rings in the benzoyl and the terephthalate units make dihedral angles of 67.05 (7)° and 57.57 (7)°, respectively, with the naphthalene ring system. There is an intramolecular C—H...O interaction between the ketonic carbonyl O atom and an H atom on the naphthalene ring system. In the crystal, C—H...O interaction of the benzene ring in the benzoyl group and weak C=O...π interaction [O...centroid = 3.375 (2) Å] of the naphthalene ring with the O atom in the ketonic carbonyl group are observed. These interactions form layers parallel to the bc plane.

Boron-modified pyrrole-based anion receptors (catechol–boron and diphenylboron dipyrrolyldiketone derivatives) formed planar receptor–anion complexes, leading to charge-by-charge assemblies with planar cations, as in the corresponding difluoroboron derivative.

A xerogel derived from the supramolecular gel of NHC-pincer Pd-complex-bound norvaline shows high catalytic activity for the intramolecular addition-cyclization of alkynoic acid and phenol derivatives in water furnishing ene-lactones in good to excellent yields.

A novel DNA base-pairing beta-hairpin peptide involving intramolecular hydrogen bonds for induction of beta-hairpin secondary structure and intermolecular complementary hydrogen bonds between thymine and diaminopyridine for molecular recognition has been synthesized.

Two-dimensional arrays of gold nanoparticles (AuNPs) as localized surface plasmon-resonant (LSPR) optics on a transparent conductive layer of indium–tin-oxide (ITO) were successfully fabricated. The typical surface coverage of the 10 nm sized AuNPs is over 87% for on ITO film roughness of ±0.2 nm. The LSPR wavelength is tunable in the range of 622–905 nm. By adjusting the LSPR wavelength to 905 nm at peak, two-photon photochromic reaction of diarylethene derivative in solution phase was demonstrated with irradiation by an incoherent near-infrared light in the range of 0.017–0.033 W/cm2 instead of a laser, thanks to the AuNP two-dimensional array.

The molecule of the title compound, C26H18F2O8S2, lies across a crystallographic twofold rotation axis. The benzene rings of the 4-fluorobenzoyl groups make dihedral angles of 78.93 (12)° with the naphthalene ring system. An intramolecular C—H...π interaction occurs. In the crystal, a number of C—H...O interactions link the molecules, forming a three-dimensional structure.

The title compound, [Pt(C15H18NO2S)Cl], was obtained by the cyclo­metallation reaction of cis-bis­(benzonitrile)dichlorido­platinum(II) with N-benzyl­idene-l-methio­nine allyl ester in refluxing toluene. The PtII atom has a square-planar geometry and is tetra-coordinated by the Cl atom and the C, N and S atoms from the benzyl­idene methio­nine ester ligand. In the crystal structure, the S atoms show opposite chiral configurations with respect to the α-carbon of the methio­nine, reducing steric repulsion between the methyl and allyl ester groups.