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241.
The atom‐transfer carbonylation reaction of various alkyl iodides thereby leading to carboxylic acid esters was effectively accelerated by the addition of transition‐metal catalysts under photoirradiation conditions. By using a combined Pd/ reaction system, vicinal C‐functionalization of alkenes was attained in which α‐substituted iodoalkanes, alkenes, carbon monoxide, and alcohols were coupled to give functionalized esters. When alkenyl alcohols were used as acceptor alkenes, three‐component coupling reactions, which were accompanied by intramolecular esterification, proceeded to give lactones. Pd‐dimer complex [Pd2(CNMe)6][PF6]2, which is known to undergo homolysis under photoirradiation conditions, worked quite well as a catalyst in these three‐ or four‐component coupling reactions. In this metal/radical hybrid system, both Pd radicals and acyl radicals are key players and a stereochemical study confirmed the carbonylation step proceeded through a radical carbonylation mechanism.  相似文献   
242.
The solution‐dispersed‐state and polymer‐dispersed‐state circular dichroism (CD) and circularly polarized luminescence (CPL) properties of chiral binaphthyl fluorophores could be controlled by the choice of open‐ or closed‐type substituents on the binaphthyl units and by the axial chirality of the binaphthyls.  相似文献   
243.
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, R1COOH, or amines, R2NH2, to give the corresponding N‐/C‐functionalized norvalines R1‐D /L ‐[PdCl(dpb)]Nva‐R2 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.  相似文献   
244.
Pentacyanocyclopentadienide (PCCp?), a stable π‐electronic anion, provided various ion‐pairing assemblies in combination with various cations. PCCp?‐based assemblies exist as single crystals and mesophases owing to interionic interactions with π‐electronic and aliphatic cations with a variety of geometries, substituents, and electronic structures. Single‐crystal X‐ray analysis revealed that PCCp? formed cation‐dependent arrangements with contributions from charge‐by‐charge and charge‐segregated assembly modes for ion pairs with π‐electronic and aliphatic cations, respectively. Furthermore, some aliphatic cations gave dimension‐controlled organized structures with PCCp?, as observed in the mesophases, for which synchrotron XRD analysis suggested the formation of charge‐segregated modes. Noncontact evaluation of conductivity for (C12H25)3MeN+ ? PCCp? films revealed potential hole‐transporting properties, yielding a local‐scale hole mobility of 0.4 cm2 V?1 s?1 at semiconductor–insulator interfaces.  相似文献   
245.
(+)-Alternamin (1), a new dihydrofuranocoumarin, was isolated from the aerial parts of Murraya alternans (Kurz) Swingle. The analysis 2-D NMR correlation of (+)-1 led to either of linear dihydrofuranocoumarin (2A, 2C) or angular one (2B). An IR and a vibrational circular dichroism (VCD) studies were conducted to distinguish the structure and to assign the absolute configuration. By comparison of the observed spectra with the calculated spectra for (S)-2A, (S)-2B, and (R)-2C, the molecular structure of (+)-1 was determined to be (S)-(+)-5,8-dimethoxymarmesin. The compound exhibited antidote activity against snake venom from Trimeresurus flavoviridis, affording experimental support for the pharmacological use of M. alternans.  相似文献   
246.
Star polymers containing ruthenium complex in the core were prepared by ruthenium-catalyzed living radical polymerization, where the metal catalysts were directly encapsulated on linking reactions of living poly(MMA) in the presence of ethylene glycol dimethacrylate as a linker and diphenyl-4-styrylphosphine as a ligand incorporated in the core. The products were characterized by SEC/MALLS, UV-vis, NMR, AFM, TEM, and ICP-AES and were employed as polymer catalysts for the oxidation reaction of alcohol.  相似文献   
247.
Conformationally flexible hexakis-urea 1 was synthesized efficiently by condensing hexakis(aminomethyl)benzene with 4-nitrophenyl-(3,5-di-tert-butylphenyl)carbamate. The hexakis-urea 1 is unexpectedly soluble in organic solvents of low polarity due to intramolecular hydrogen bonding. The hexakis-urea 1 recognizes chloride, bromide, and acetate in a 1:2 host-guest ratio and in a positive allosteric manner in CDCl3. The ability of 1 to recognize dihydrogen phosphate is a unique outcome, and the structure of the associated complex, which contains four dihydrogen phosphate ions, was clarified by single-crystal X-ray structural analysis. However, in solution, a complex with three dihydrogen phosphate ions was identified. The dihydrogen phosphate association in CDCl3 proceeds in an amphoteric allosteric manner; in a positive allosteric manner (K1<K2) in the first step and a negative allosteric manner (K2>K3) in the subsequent step.  相似文献   
248.
Reactions of bis(o-(diphenylphosphino)phenyl)methylsilane with M(PPh(3))(4) (M = Ni, Pd, Pt) were investigated. When M = Ni or Pd, synthesis and isolation of η(2)-(Si-H) complexes of mononuclear Ni(0) and Pd(0) were achieved for the first time as frozen intermediates for oxidative addition of the Si-H bond. Structural analysis by X-ray and NMR spectroscopy disclosed that their η(2)-(Si-H) structures were maintained in both solid and solution states and coordination of the Si-H bond to the metal center was relatively weak. On the other hand, reaction with a platinum(0) complex afforded two kinds of pentacoordinate silyl platinum(II) hydride complexes having a PSiP-pincer ligand, which underwent unique thermal isomerization from a square-pyramidal cis-H-Pt-Si to a trigonal-bipyramidal trans-H-Pt-Si isomer. Mechanistic investigations revealed that this isomerization proceeded via an intramolecular rearrangement process probably through a turnstile rotation.  相似文献   
249.
[3]- and [5]-rotaxanes consisting of crown ether and ammonium salts were synthesized in high yields by a tributylphosphine-catalyzed end-capping method which provides a simple and practical means of obtaining higher-order rotaxanes.  相似文献   
250.
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