Suzuki Noriyuki

A molecular editing strategy to construct quinoxalinones from chromones and benzimidazolylidene N-heterocyclic carbenes (NHCs) was developed. The C2 atoms of the chromones were incorporated into the quinoxalinones via ring expansion of the NHCs.

Abstract: Ruthenium-catalyzed olefin metathesis reactions were conducted in water with thermoresponsiveblock copolymers forming micelles. The block copolymers were prepared by living radicalpolymerization and consisted of a thermo-responsive and hydrophilic segments. The formersegment included poly(N-isopropylacrylamide) or poly(N,N-diethylacrylamide), and the latterpoly(sodium 4-styrene sulfonate), poly(sodium 2-acrylamido-2-methylpropanesulfonate) orpoly(ethylene glycol). Homometathesis, cross-metathesis and ring-closing metathesis reactions proceededto afford the products in moderate to good yields. Extraction efficiency from the reactionmixture was also studied.

The soil is a rich ecosystem where many ecological interactions are mediated by small molecules, and in which amoebae are low-level predators and also prey. The social amoeba Dictyostelium discoideum has a high genomic potential for producing polyketides to mediate its ecological interactions, including the unique ‘Steely’ enzymes, consisting of a fusion between a fatty acid synthase and a chalcone synthase. We report here that D. discoideum further increases its polyketide potential by using the StlB Steely enzyme, and a downstream chlorinating enzyme, to make both a chlorinated signal molecule, DIF-1, during its multi-cellular development, and a set of abundant polyketides in terminally differentiated stalk cells. We identify one of these as a chlorinated dibenzofuran with potent anti-bacterial activity. To do this, StlB switches expression from prespore to stalk cells in late development and is cleaved to release the chalcone synthase domain. Expression of this domain alone in StlB null cells allows synthesis of the stalk-associated, chlorinated polyketides. Thus, by altered expression and processing of StlB, cells make first a signal molecule, and then abundant secondary metabolites, which we speculate help to protect the mature spores from bacterial infection.

Reactions of five-membered zirconacycloalkynes and zirconacyloallenes with Cp₂Zr(H)Cl gave five membered zirconacyloallenes without work-up such as protonolysis and hydrogenolysis.

A few kinds of thermoresponsive diblock copolymers have been synthesized and utilized for palladium-catalyzed coupling reactions in water. Poly(N-isopropylacrylamide) (PNIPAAm) and poly(N,N-diethylacrylamide) (PDEAAm) are employed for thermoresponsive segments and poly(sodium 4-styrenesulfonate) (PSSNa) and poly(sodium 2-acrylamido-methylpropanesulfonate) (PAMPSNa) are employed for hydrophilic segments. Palladium-catalyzed Mizoroki–Heck reactions are performed in water and the efficiency of the extraction process is studied. More efficient extraction was observed for the PDEAAm copolymers when compared with the PNIPAAm copolymers and conventional surfactants. In the study of the Sonogashira coupling reactions in water, aggregative precipitation of the products was observed. Washing the precipitate with water gave the product with satisfactory purity with a good yield.

Cynaropicrin is found in artichoke (Cynara scolymus) and is the source of its bitter taste and it is a sesquiterpene lactone with a 5-7-5 tricyclic skeleton, six chiral centers, and four exo-olefins. This natural product has numerous attractive biological activities including the inhibition of NF-kappa B activation, antihepatitis C activity, and antitrypanosomal activity. In this study, the first total synthesis of cynaropicrin was achieved starting from (S)-alpha-pinene. The synthesis involved a stereoselective Favorskii rearrangement and an indium-promoted diastereoselective Barbier reaction.

Five-membered metallacycloallene compounds, 1-zirconacyclopenta-2,3-dienes 1, derived from but-1- en-3-ynes 2 and low-valent zirconocene, reacted with esters and isocyanates. Reactions of 1 with car- boxylic esters such as ethyl acetate and methyl benzoate resulted in the formation of alkynyl ketones after hydrolysis, albeit in low yields, and diethyl carbonate gave alkynyl esters in moderate yields. Insertion of isocyanates such as phenylisocyanate to the ZreC bond of 1 afforded an alkynyl amide when 1 had substituents at the 2,4-positions (1a), while the zirconium complexes 1 that had silyl groups at the 2,5-positions, 1b and 1c, gave dienyl amides after hydrolysis. These reactions involved C]O insertion into the Zr-Csp3 bond in 1. It is likely that the insertion afforded seven-membered 1-oxa-2- zirconacyclohepta-3,4-diene intermediates first, whilst the reaction of 2,5-disilyl-1-zirconacyclopenta- 2,3-dienes 1b-c with isocyanates formed five-membered 1-oxa-2-zirconacyclopent-3-ene intermediates. Additional CeC bond formation reactions of these intermediates via transmetallation to copper salts followed by addition of allyl halides furnished allylated products.

L-Proline was covalently tethered on thermoresponsive ionic block copolymers that formed micelles in aqueous solutions. The block copolymers consisted of a poly(N-isopropylacrylamide) (PNIPAAm) segment and an anionic or cationic polymer segment. These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 35–40 °C, and achieved thermal stimuli-induced formation and dissociation of micelles. The copolymer generated micelles in aqueous solution at higher temperature, where a catalytic aldol reaction proceeded with high diastereo- and enantioselectivities. The micelles dissociated at lower temperature to form a clear solution such that the products could be efficiently extracted from the aqueous reaction mixture. Extraction of the aldol product with organic solvent from the aqueous solution of the anionic copolymer was more efficient than from the nonionic copolymer solution.

Palladium-catalyzed Mizoroki-Heck reactions were carried out in water using thermoresponsive polymer micelles. The micelles were generated from thermoresponsive block copolymers consisting of a poly(N-isopropylacrylamide) (PNIPAAm) segment and a hydrophilic segment such as nonionic poly(ethylene glycol) (PEG) (2) and anionic poly(sodium p-styrenesulfonate) (PSSNa) (9). These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 40-50 deg and showed thermal stimuli-induced formation and dissociation of micelles. The copolymers formed micelles in aqueous solution at higher temperature, where catalytic reactions proceeded. At lower temperature, the micelles dissociated to form a clear solution, enabling efficient extraction of the products from aqueous reaction mixture. In the presence of these copolymers, palladium complexes catalyzed the coupling reactions between aryl iodides and alkene compounds inside the hydrophobic micelle cores in water under relatively milder conditions. Extraction of the products from the aqueous solution of 2 or 9 was found to be efficient enough in comparison with conventional surfactants.

Five-membered metallacycloallene compounds, 2,5-disubstituted 1-zirconacylopenta-2,3-dienes were prepared from (E)-1,4-trialkylsilylbut-1-en-3-ynes in good yields. The structures of these compounds were determined by X-ray diffraction study. Contrary to our previous study on 2,4-disubstituted 1-zirconacylopenta-2,3-dienes, which gave alkynyl alcohols by the reaction with ketones after hydrolysis, the 2,5-bis(trialkylsilyl) complexes reacted with ketones to afford allenyl alcohols. Reactions with a nitrile gave a pyrolle compound probably via the formation of seven-membered 1-aza-2-zirconacylcohepta-3,4,7-triene compounds. When the (E)-1,4-bis(trialkylsilyl)but-1-en-3-ynes were treated with titanium isopropoxide/n-butyllithium followed by reaction with nitriles, the corresponding alkynyl ketones were obtained.

A multidentate O,N,O[sbnd]P ligand 4 designed for early–late heterobimetallic (ELHB) complexes was synthesized. The ligand 4 has an O,N,O-tridentate ligand moiety and a triarylphosphine group. The O,N,O-moiety based on lutidine scaffold selectively coordinated to early transition metals such as titanium and niobium in the reaction with the corresponding metal alkoxides to form mononuclear complexes. Coordination of the triarylphosphine moiety to the niobium atom was negligible in the Nb-ONO[sbnd]P complex according to 31P NMR spectroscopy, whereas a part of the phosphorus atom coordinated to the titanium atom in the Ti-ONO[sbnd]P complex. Addition of [PdCl(π-allyl)]2 or [RhCl(cod)]2 to the Nb-ONO[sbnd]P complex gave rise to the formation of ELHB complexes. Thus, the one-pot preparation of ELHB complexes was achieved by simple procedure.

The reactivity of the bidentate ancillary ligand 1,2-bis(dimethylphosphino)ethane (dmpe), Me2PCH2CH2PMe2, involving low-valent zirconium complexes was studied. Negishi reagent, Cp2Zr(n-Bu)(2), gave zirconocene but-l-ene complexes of monocoordinated dmpe, while dicoordinated Cp2Zr(K-2-dmpe) was not formed. Cp2ZrEt2 reacted with dmpe to afford Cp2Zr(eta(2)-ethene)(kappa(1)-dmpe) (2) and [Cp2Zr(eta(2)-ethene)](2)(mu,kappa(1)-dmpe) (3). Cp2Zr(K-2-dmpe) (1) prepared by reduction of Cp2ZrCl2 with Li in the presence of dmpe reacted with alkynylimine and alkynylthioamide to give the corresponding 1-aza-2-zirconacyclopenta-3,4-diene (6) and 1-thia-2-zirconacyclopenta-3,4-diene (8), respectively, whereas neither conjugated 1-en-3-ynes nor alkynes gave zirconacycle products. Reactions of 1 with iodomethane brought about oxidative addition of C-I to afford Cp2Zr(Me)X (X = Cl, I) species. (C) 2017 Elsevier B.V. All rights reserved.

A Ph3PAuCl–SnCl2 composite, prepared in situ from Ph3PAuCl and SnCl2, catalyzed the formation of 1-benzopyrans from phenols and phenylacetylene. The Ph3PAuCl–SnCl2 composite catalyzed reaction was presumed to proceed through the successive ortho-alkenylation and O-alkenylation of phenols with phenylacetylene followed by cyclization of the prepared ortho- and O-dialkenylated phenol derivatives. Conveniently, all reactions with Ph3PAuCl–SnCl2 composite were established without rigorous exclusion of air and water.

Background: Conducting organic reactions in water as a solvent have attracted chemists because of its environmentally benign property. However, it often suffers practical difficulties since most of organic compounds are insoluble in water. One promising methodology to improve the reactivity in water is to use surfactants that emulsify the organic/water mixture. Efficient extraction from the emulsified mixture is necessary to reduce the usage of organic solvent. Methods: We designed polymer micelle that can be turned on and off by temperature-stimuli. Poly(N-isopropyl acrylamide), known as thermoresponsive polymer, was copolymerized with the acrylate ester of 4-hydroxy-L-proline using a reversible addition/fragmentation chain transfer polymerization (RAFT) reagent that contains a poly(ethylene glycol) (PEG) chain to obtain a polymer-tethered organocatalyst. The L-proline moieties were immobilized on a thermoresponsive amphiphilic diblock copolymer that consists of poly(N-isopropyl acrylamide) (PNIPAAm) and linear PEG fragments. The copolymer dissolved in water to form clear solution at room temperature, whereas the solution turned opaque at 50 °C, indicating the micelle formation. Results: The aldol reaction of 4-nitrobenzylaldehyde and cyclohexanone was catalyzed with the copolymer micelles, and the product was obtained in good yield with excellent diastereo- and enantioselectivity. Both the yield and stereoselectivity were superior to those obtained by using our previously developed proline-immobilized “broom”-type PNIPAAm-b-PEG copolymer catalysts. The Michael reaction was also catalyzed by the “linear”-type PNIPAAm-b-PEG catalyst and resulted in moderate yields with good stereoselectivity. Conclusion: We have synthesized a series of “linear” thermoresponsive block copolymers on which L-proline moieties were immobilized. The polymer catalyst formed micelles at 50 °C. The aldol reaction was catalyzed by the copolymer in water with high diastereo- and enantioselectivity. The catalytic performance of the linear copolymer was superior to that of the similar “broom”-type copolymer. The polymer catalyst also catalyzed the enantioselective Michael addition reaction.

Heterobimetallic complexes containing titanium and palladium were prepared from O,N,O-N,N multidentate ligands. The ligands each contained an O,N,O-tridentate part based on a 2,6-lutidine scaffold and an N,N-bidentate di(pyridin-2-yl) part. The O,N,O-moiety selectively coordinated to a titanium atom on treatment with titanium(tetraisopropoxide), although one of the di(pyridin-2-yl) groups in the N,N-moiety coordinated to the titanium atom. The N,N-bidentate di(pyridin-2-yl) moiety coordinated to the palladium atom on treatment with bis(benzonitrile)palladium(II) chloride to afford a heterobimetallic complex. The dynamic behavior of the complexes in solution was studied by NMR spectroscopy. Heterobimetallic complexes containing titanium and palladium were prepared from O,N,O-N,N multidentate ligands and structurally characterized.

Isodesmosine is a crosslinking pyridinium amino acid of elastin and is an attractive biomarker for the diagnosis of chronic obstructive pulmonary disease (COPD). In this paper, we describe the total synthesis of isodesmosine. The key features of this synthesis are stepwise and regioselective palladium-catalyzed Negishi and Sonogashira cross-coupling reactions for efficient introduction of amino acid segments on the pyridine ring. The total synthesis of isodesmosine, a crosslinking amino acid of elastin and an attractive biomarker of COPD, has been achieved by stepwise and regioselective Negishi and Sonogashira cross-coupling reactions.

Stable five-membered metallacyclic allenes that contain a sulfur atom were synthesized and structurally characterized. Low-valent zirconocene and titanocene reacted with alkynylthioamides to afford 1-thia-2-metallacyclopenta-3,4-diene compounds in moderate to excellent yields. The molecular structure of the zirconium complexes indicated their cycloallene structure, while an eta(2)-alkyne-coordinated structure might be more responsible for the titanium complexes. Hydrolysis of the compounds gave the corresponding (Z)-alkenylthioamides predominantly. Deuterolysis resulted in >99% D incorporation.

Zirconium complexes of some [5]cumulene derivatives were studied for their variable coordination modes and haptotropic shifts. Some [5]cumulene compounds reacted with zirconocene(II) species to afford 1-zirconacyclopent-3-yne complexes that have five-membered cycloalkyne structures. Only a few [5]cumulene compounds afforded eta(2)-coordinated complexes in the presence of neutral ligands such as trimethylphosphine and tert-butyl isocyanide. Interconversion between the five-membered structure and the eta(2)-complex was observed. Investigation of [5]cumulene derivatives of various cycloalkylidene moieties indicated that the eta(2)-complex was preferred when the [5]cumulene has bulkier substituents. A [5]cumulene with 2,2,6,6-tetramethylcyclohexylidene groups much preferred the 1-zirconacyclopent-3-yne structure to eta(2)-coordination. In sharp contrast, the eta(2)-coordinated complex was favored for a [5]cumulene with 2,2,7,7-tetramethylcycloheptylidene groups in the presence of PMe3. Small differences in steric environments caused totally different reactivity in [5]cumulene complexes. DFT calculations on the formation enthalpy were consistent with the experimental results, although that cannot fully rationalize the difference.

The Negishi cross-coupling reaction of an organozinc derivative prepared from protected l-aspartic acid with monohalopyridines was improved by employing a combination catalyst of Pd2(dba)3 and P(2-furyl) 3 and removing an extra Zn from the organozinc reagent via centrifugation. The reactivity of halogenated pyridines (Cl, Br, I) with substituents at the C2, C3, and C4 positions of the pyridine ring was investigated, and it was found that the use of 4-iodopyridine as a substrate gave the best yield (90%) for the cross-coupling reaction. © 2013 HeteroCorporation.

Tin(II) chloride, which is insensitive to water and air, mediated the coupling reaction between alkynes and aldehydes as a Lewis acid in nitromethane to produce (E)-α,β-unsaturated ketones by a skeletal transformation in which one alkynic carbon atom changed into an oxo carbon atom accompanied by the cleavage of a C=O bond in the starting aldehydes. This coupling reaction was promoted by a catalytic amount of a primary or secondary alkanol. The coupling reaction between 1-deuterio-2-phenylethyne and benzaldehyde with BuOH afforded 1,3-diphenyl-2-deuterio-2-propenone (2-deuteriation: 94 % D), whereas the coupling reaction between phenylethyne and benzaldehyde with BuOD afforded 1,3-diphenyl-2-propenone (2-deuteriation: 0 % D). Because almost no exchange between hydrogen and deuterium at the 2-position of 1,3-diphenyl-2-propenone occurs in either of the reactions, the coupling reaction between alkynes and aldehydes with tin(II) chloride is presumed to proceed by nucleophilic addition of alkynes to aldehydes. The cleavage of the C-O single bond generated by the nucleophilic addition might be induced by the strong oxophilicity of tin. Coupling reactions occur between alkynes and aldehydes mediated by tin(II) chloride as a Lewis acid to produce (E)-α,β-unsaturated ketones by a skeletal transformation in which an alkynic carbon atom changes into an oxo carbon atom accompanied by cleavage of the C=O bond in the starting aldehydes. This coupling reaction is promoted by a catalytic amount of a primary or secondary alkanol. Copyright © 2013 WILEY-VCH Verlag GmbH &amp Co. KGaA, Weinheim.

Seven-membered metallacyclic allene compounds, 1-zirconacyclohepta-2,3,6-trienes, were synthesized by intermolecular coupling between alkynes and 1-en-3-ynes on a zirconium atom. X-ray diffraction studies and NMR spectroscopic observation indicated their seven-membered structures, although the contribution from 2-alkynyl-1-zirconacyclopent-4-ene might be considered. Benzyne, an unstable alkyne, also coupled with 1-en-3-ynes on zirconium and titanium. (C) 2013 Elsevier B.V. All rights reserved.

The cyclotrimerization of terminal alkynes, such as ethyl propynoate, arylacetylenes, and alkylacetylenes, catalyzed by phosphine-free [IrCl(cod)]2 is induced by a catalytic amount of tin(II) chloride in 1,4-dioxane to afford 1,2,4- and/or 1,3,5-trisubstituted benzenes. Terminal α,ω-diynes also undergo the cyclotrimerization with monoynes to form bicyclic benzene derivatives. cod=1,5-cyclooctadiene.

A weak Lewis acid, tin(II) chloride, which is insensitive to water and air, functioned as a catalyst for the propargylic substitution of secondary propargylic alcohols with carbon nucleophiles, such as electron-rich arenes, heteroarenes, and 1,3-dicarbonyl compounds, and nitrogen nucleophiles, such as sulfonamides, carbamates, and carboxamides, at 40-80 °C in CH 3NO2 under air and exhibited a higher catalytic activity than tin(II) bromide or iodide in the propargylic substitution of 1-phenyl-2-propyn-1-ol with anisole at 40 °C in CH3NO 2. The solubility of tin(II) fluoride in CH3NO2 would have to be extremely low to cause no propargylic substitution. 1-Phenyl-substituted propargylic alcohols readily reacted with all these nucleophiles, whereas 1-(4-cyanophenyl)-2-propyn-1-ol and 1-(pentafluorophenyl)- 2-propyn-1-ol did not react at all with 1,2,3-trimethoxybenzene even in CH 3NO2 at reflux. The 1-alkyl-substituted secondary propargylic alcohol, 1,5-diphenyl-1-pentyn-3-ol, underwent SnCl 2-catalyzed propargylic substitution with electron-rich arenes and amides, although the reaction was slow even at 80 °C in CH 3NO2. Thus, the SnCl2-catalyzed propargylic substitution reaction is dependent upon the stability of the propargylic carbenium ion formed upon elimination of hydroxide from the corresponding propargylic alcohol. Copyright © 2013 WILEY-VCH Verlag GmbH &amp Co. KGaA, Weinheim.

Carbon-carbon bond formation reactions of a silyl-substituted [3]cumulene, (2)-1,4-bis(trimethylsilyl)buta-1,2,3-triene (1), with alpha,beta-unsaturated carbonyl compounds in the presence of Lewis acids are presented. The reactions gave 1,3-enyne compounds bearing a carbonyl moiety, and the silyl groups of 1 were maintained in the products. The reaction of 1,4-dideuterated 1-d(2) suggested that the C-C bond formation proceeds by an ene reaction mechanism. (C) 2013 Elsevier Ltd. All rights reserved.

Seven-membered metallacycloalkyne compounds were synthesized. The reaction of the zirconocene-ethylene complex and (Z)-1,4-bis(trimethylsilyl)buta-1,2,3- triene gave a mixture of 1-zirconacyclopent-3-yne and 1-zirconacyclohept-3-yne. In contrast, zirconocene-alkyne complexes, such as those of 1-(trimethylsilyl) prop-1-yne and diphenylacetylene, gave 1-zirconacyclohept-2-en-5-yne in good yields. Consideration of structural parameters suggests that both a seven-membered cyclic alkyne and a five-membered structure contribute to generation of this complex. Coupling of benzyne and [3]cumulenes on a metal was also found to afford the corresponding metallacycles. Seven-membered metallacycloalkyne compounds were synthesized and structurally characterized. Zirconocene-alkyne complexes, such as those of 1-(trimethylsilyl)prop-1-yne and diphenylacetylene reacted with [3]cumulene to give 1-zirconacyclohept-2-en-5-yne in good yields. Coupling of benzyne and [3]cumulenes on the metal also gave the corresponding metallacycles. Copyright © 2013 WILEY-VCH Verlag GmbH &amp Co. KGaA, Weinheim.

L-Proline moieties, which serve as organocatalysts, were tethered on block copolymers that consisted of thermoresponsive poly(N-isopropylacrylamide) and PEG-grafted polyacrylate blocks. The copolymer dissolved in water under the LCST (25 °C), while they formed micelle above the LCST (50 °C). Aldol reactions between an aryl aldehyde and a ketone were conducted in this aqueous solution. The aldol products were obtained in high yield with high diastereo- and enantioselectivity (96% ee). The catalyst solution could be reused up to three times.

O,N,O-tridentate ligands 2-H-2 based on a 2,6-substituted pyridine structure and their dichlorotitanium complexes 3 were synthesized and structurally characterized. The complexes have five-coordinated, trigonal bipyramidal structure, in which one chlorine atom was located at trans-position to the nitrogen atom of the pyridine ring and the other was at cis-position. NMR spectroscopy indicated their fluxional structure in solution. The complexes showed low to modest catalytic activity for ethylene polymerization in the presence of methylaluminoxane (MAO) as a co-catalyst. (C) 2012 Elsevier B.V. All rights reserved.

Reaction of η2-iminozirconocene chloride complexes with trimethylsilylethynyl lithium yields the corresponding five-membered aza-zirconacycloallenoids, which were also obtained from in situ generated zirconocene with alkynyl imines.

The stereoisomerization of 2,5-disubstituted 1-zirconacyclopent-3-yne compounds, stable five-membered cycloalkynes, has been studied with regard to the mechanism. The bimetallic complex of 1,4-bis(trimethylsilyl)butatriene was synthesized and structurally characterized, although it seems unimportant for the stereoisomerization reactions. The isomerization of trans-1,1-bis(eta(5)-cyclopentadienyl)-2,5-bis(trimethylsilyl)-1-zirconacyclopent-3-yne 2a into the cis-form in benzene-d(6) solution were observed using H-1 NMR spectroscopy at 50 degrees C in various concentrations. The reaction was first order with respect to trans-2a. This ruled out the possibility that a bimetallic complex was responsible for the isomerization. A kinetic isotope effect was observed (k(H)/k(D) 1.8), suggesting that C-H activation is involved in the rate-determining step. A mechanism via hydrogen elimination from the complex of eta(4)-pi,pi-coordination mode is proposed. (C) 2011 Elsevier B.V. All rights reserved.

Palladium(II)-exchanged hydroxyapatite (PdHAP; Pd/Ca ratio = ca. 1/200) was prepared by ion-exchanging with Ca2+ from calcined hydroxyapatite (2.0 mmol) and Pd(NO3)(2) (0.10 mmol) in water (150 mL) at 70 degrees C for 24h. The PdHAP (1 mol% Pd to aryl bromides) functioned as a catalyst for the Suzuki-Miyaura-type cross-coupling reaction of aryl bromides and potassium aryltrifluoroborates with triphenylphosphine (1 mol%) and excess potassium carbonate at 50 degrees C in methanol under air. This cross-coupling reaction was found to proceed in water, while the rate was slow compared with that in methanol. The heterogeneous PdHAP catalyst was used ten times repeatedly at 50 degrees C in methanol under air, though its catalytic activity gradually declined. XRD and XRF analyses and TEM images revealed that most of palladium species would still be supported as isolated ions on the repeatedly used PdHAP, in spite of the changes of the structure and composition of PdHAP surface at the late stages in the repetitive uses and the partial leaching of Pd species at the initial stages in the repetitive uses. The gradual decline of the catalytic activity might be dependent on either the changes of PdHAP surface at the late stages or the partial leaching of Pd species at the initial stages. Still, heterogeneous PdHAP served as a reusable catalyst for Suzuki-Miyaura-type cross-coupling reaction with potassium aryltrifluoroborates. (C) 2011 Elsevier B.V. All rights reserved.

Desmosine, a crosslinking amino acid of elastin, is an attractive biomarker for diagnosis of chronic obstructive pulmonary disease (COPD). In this study, the first total synthesis of (+)-desmosine was achieved in 11% overall yield in 13 steps utilizing stepwise and regioselective Sonogashira cross-coupling reactions.

Copper(II)-exchanged hydroxyapatite, prepared by ion-exchanging of Ca(II) in calcium hydroxyapatite [Ca-10(PO4)(6)(OH)(2)] with Cu(NO3)(2) at 70 degrees C in water, functions as a reusable heterogeneous catalyst with neither reducing agents nor bases for azide-alkyne [3+2] cycloaddition at 50 degrees C in water under air. (C) 2011 Elsevier Ltd. All rights reserved.

The E isomer of a [5]cumulene derivative, 2,2, 9,9-tetramethyl-3,8-diphenyldeca-3,4,5,6,7-pentaene (1), which was previously believed to be unisolable owing to very fast E/Z isomerization, was isolated and structurally characterized. The Z isomer was trapped as the transition-metal complex 5, and the molecular structure was determined. DFT calculations and an electrochemical study on 1 are also described.

Ruthenium complexes bearing ethylbis(2-pyridylethyl)amine (ebpea), which has flexible -C2H4- arms between the amine and the pyridyl groups and coordinates to a metal center in facial and meridional modes, have been synthesized and characterized. Three trichloro complexes, fac-[(RuCl3)-Cl-III-(ebpea)] (fac-[1]), mer-[(RuCl3)-Cl-III(ebpea)] (mer-[1]), and mer-[(RuCl3-)-Cl-II{eta(2)-N(C2H5)(C(2)H(4)py)=CH-CH(2)py}] (mer-[2]), were synthesized using the Ru blue solution. Formation of mer-[2] proceeded via a C-H activation of the CH2 group next to the amine nitrogen atom of the ethylene arm. Reduction reactions of fac- and mer-[1] afforded a triacetonitrile complex mer- [Ru-II((CHCN)-C-3)(3)(ebpea)(PF6)(2) (mer-[3](PF6)(2)). Five nitrosyl complexes fac-[RuX2(NO) (ebpea)]PF6 (X = Cl for fac-[4]PF6; X = ONO2 for fac-[5]PF6) and mer-[RuXY(NO)(ebpea)]PF6 (X = Cl, Y = Cl for mer-[4]PF6; X = Cl, Y = CH3O for mer-[6]PF6; X = Cl, Y = OH for mer-[7]PF6) were synthesized and characterized by X-ray crystallography. A reaction of mer-[2] in H2O-C2H5OH at room temperature afforded mer-[1]. Oxidation of C2H5OH in H2O-C2H5OH and i-C3H7OH in H2O-i-C3H7OH to acetaldehyde and acetone by mer-[2] under stirring at room temperature occurred with formation of mer-[1]. Alternative C-H activation of the CH2 group occurred next to the pyridyl group, and formation of a C-N bond between the CH moiety and the nitrosyl ligand afforded a nitroso complex [Ru-II(N-3)(2){N(O)CH(py)CH2N(C2H5)C(2)H(4)py}] ([8]) in reactions of nitrosyl complexes with sodium azide in methanol, and reaction of [8] with hydrochloric acid afforded a corresponding chloronitroso complex [(RuCl2)-Cl-II{N(O)CH(py)CH2N(C2H5)C(2)H(4)py}] ([9]).

A five-membered metallacycloallene complex, 1-zirconacyclopenta-2,3-diene, was prepared from low-valent zirconocene and 2,4-bis(trimethylsilyl)but-1-en-3-yne. The complex reacted with carbonyl compounds to afford alkynyl alcohols after hydrolysis via C=O insertion into Zr-C bond. Similarly, nitriles inserted into the Zr-C bond to give the corresponding ketones after hydrolysis. The insertion of C=O and CN selectively took place at zirconium-sp(3) carbon of the metallacycle.

In this account [3]- and [5]cumulene complexes of group 4 metallocenes that form five-membered metallacycles are described. These complexes have a "triple bond" despite their five-membered ring structure, showing that they are regarded as 1-metallacyclopent-3-ynes. The molecular structures show their strained alkyne character. These complexes react with transition metals to form alkyne-coordinated bimetallic complexes. They also receive electrophilic attack by protons and boranes resulting in M-C bond cleavage. When a [3]cumulene couples with an alkyne on the metal, the reaction produces seven-membered metallacycloalkynes that have a strained structure showing an interaction between the "triple bond" and the metal center. Hexapentaenes. [5]cumulenes, form conjugated 1-metallacyclopent-3-ynes. The aryl-substituted [5]cumulene complex was reduced by alkali metal to give dianionic species that reacted with protons to give 1-metallacyclopent-3-ene, a cycloalkene, and with iodomethane to give 1-metallacyclopenta-2,3-diene, a cycloallene. The hexapentaene with tert-butyl groups reacts with zirconocene to form an eta(2)-pi-coordinated complex in the presence of trimethylphosphine, although it gave a 1-metallacyclopent-3-yne in the absence of the phosphine. The former was transformed into the latter by addition of a phosphine, and vice versa by removing the phosphine, showing a "haptotropic" shift. (C) 2009 Elsevier B.V. All rights reserved.

The (iminium ion)ruthenium(II) complex mer(Cl, Cl,Cl)-[RuCl(3){eta(2)-NCHCH(2)py(C(2)H(4)py)C(2)H(5)}] was synthesized via a C-H activation of the bridging ethyl group of an ethylbis(2-pyridylethyl)amine ligand and characterized by X-ray structural analysis. Oxidations of alcohols by the (iminium ion)ruthenium(11) complex occurred with generation of mer-[Ru(III)Cl(3)(ebpea)].

The first highly selective 1:2 cross-trimerization between triisopropylsilytacetylene and 2 equiv of internal alkynes, leading to 1,3-diene-5-yne compounds, was achieved using the Ni(cod)(2)/P(n)Pr(3) catalyst. Various symmetrical and asymmetrical internal alkynes could be used for the cross-trimerization reaction with high regio- and stereoselectivity.

Low-valent zirconocene species reacted with 1,1,6,6-tetraalkyl-1,2,3,4,5-hexapentaenes to form both 1-zirconacyclopent-3-ynes and n(2)-pi-coordinated complexes according to the alkyl groups (R) and the existence of the neutral ligand (L). Haptotropic interconvertion between these two complexes was observed. It was proposed that double insertion of isocyanide into the Zr-C bond of 1-zirconacyclopent-3-ynes takes place via the isocyanide adduct of the eta(2)-pi-complex as an intermediate.

We measured steady-state fluorescence of cis-stilbene in solution, by carefully separating the contribution of coexisting trace amount of trans isomer. The obtained 'pure' fluorescence spectrum of cis-stilbene shows a broad structureless band (peaked around 420 nm) extending to the wavelength region as long as 700 nm. Compared to the fluorescence intensity from the coexisting trans isomer, the oscillator strength of the cis fluorescence was evaluated as 0.17, which indicated that the S(1) state of cis-stilbene is an optically allowed state. (C) 2008 Elsevier B.V. All rights reserved.

Reactions of ruthenium complexes having 2-pyridinecarboxylato and 2,2'-bipyridine ligands with sodium azide in alcohol afforded nitrido-bridged diruthenium complexes, [{Ru(OR)(pyca)(bpy)}(2)(mu-N)](+) (R = CH3, C2H5). Diruthenium complexes showed diamagnetic properties, a linear Ru-N-Ru coordination configuration, and two irreversible oxidation waves and two reversible reduction waves.

The new iridium(I)-guanidinate complex served as an efficient catalyst for phosphine-dependent selective cross-dimerization between silylacetylene and terminal alkyl- or arylacetylene. Especially, in case of cross-dimerization between silylacetylene and alkylacetylene, E/Z selectivity of resulting enynes could be controlled by changing phosphine.