Synthesis, Structures, and Norbornene Polymerization Behavior of <i>o</i>‑Aryloxide-Substituted NHC-Ligated σ, π‑Cycloalkenyl Palladium Complexes

Treatment of the pro-ligand (2-OH-3,5-^<i>t</i>Bu₂C₆H₂)­(Mes)­(C₃H₃N₂)⁺Br^– (<b>2a</b>) with di­[μ-chloro-2η²,5η¹-(6-methoxy-<i>endo</i>-bicyclo­[2.2.1]-hept-2-enyl)­palladium­(II)] (<b>1a)</b> and K₂CO₃ in dioxane, or reaction of the pro-ligand <b>2a</b> subsequently with ^<i>n</i>BuLi and <b>1a</b> in THF afforded the <i>o</i>-aryloxide-substituted NHC-ligated σ, π-cycloalkenyl palladium complex <b>3</b>. Similarly, treatment of the pro-ligands (2-OH-3,5-^<i>t</i>Bu₂C₆H₂)­(R)­(C₃H₃N₂)⁺Br^– [R = Mes (<b>2a</b>), Me (<b>2b</b>), ^<i>i</i>Pr (<b>2c</b>), Ph (<b>2d</b>)] with bis­[μ-chloro-1η²,5η¹-(6-ethoxy-<i>exo</i>-5,6-dihydrodicyclopentadienyl)­palladium­(II)] (<b>1b</b>) and K₂CO₃ in dioxane afforded the desired products <b>4</b>–<b>9</b>. All these complexes were fully characterized by ¹H and ¹³C NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. Single-crystal X-ray diffraction analysis results further confirmed the molecular structures of <b>3</b>–<b>6</b>. With methylaluminoxane (MAO) as cocatalyst, these complexes showed excellent catalytic activities up to 10⁷ g of PNB (mol of Pd) ^–1 h^–1 in the addition polymerization of norbornene

Synthesis, Structures, and Norbornene Polymerization Behavior of N‑Heterocyclic Carbene-Sulfonate-Ligated Palladacycles

A series of new N-heterocyclic carbene-sulfonate (NHC-sulfonate) ligands <b>5a</b>–<b>e</b> were synthesized. Treatment of the NHC-sulfonate ligands with Ag₂O and palladacycles {[Pd­(OAc)­(8-Me-quin-H)]₂ or [Pd­(dmba)­(μ-Cl)]₂ (dmba = Me₂NCH₂C₆H₅)} yielded the desired C­(sp³),N-chelated and C­(sp²),N-chelated NHC-sulfonate palladacycles <b>6a</b>–<b>e</b> and <b>7a</b>–<b>e</b> in high yields. All these complexes were fully characterized by ¹H and ¹³C NMR, high-resolution mass spectrometry, and elemental analysis. The molecular structures of compounds <b>5a</b>, <b>6d</b>, <b>6e</b>, and <b>7e</b> were determined by single-crystal X-ray diffraction analysis. In the presence of MAO, the C­(sp³),N-chelated NHC-sulfonate palladacycles <b>6a</b>–<b>e</b> showed excellent catalytic activities [10⁷ g of polynorbornene (PNB) (mol of Pd)⁻¹ h^–1], while the C­(sp²),N-chelated palladacycles <b>7a</b>–<b>e</b> showed moderate catalytic activities [10⁶ g of PNB (mol of Pd)⁻¹ h^–1] in the vinyl polymerization of norbornene. The C­(sp²),N-chelated palladacycles <b>7a</b>–<b>e</b> showed high thermal stability and reached the highest activities at high temperature (100 °C)

DNA Fingerprinting of Chinese Melon Provides Evidentiary Support of Seed Quality Appraisal

<div><p>Melon, <em>Cucumis melo</em> L. is an important vegetable crop worldwide. At present, there are phenomena of homonyms and synonyms present in the melon seed markets of China, which could cause variety authenticity issues influencing the process of melon breeding, production, marketing and other aspects. Molecular markers, especially microsatellites or simple sequence repeats (SSRs) are playing increasingly important roles for cultivar identification. The aim of this study was to construct a DNA fingerprinting database of major melon cultivars, which could provide a possibility for the establishment of a technical standard system for purity and authenticity identification of melon seeds. In this study, to develop the core set SSR markers, 470 polymorphic SSRs were selected as the candidate markers from 1219 SSRs using 20 representative melon varieties (lines). Eighteen SSR markers, evenly distributed across the genome and with the highest contents of polymorphism information (PIC) were identified as the core marker set for melon DNA fingerprinting analysis. Fingerprint codes for 471 melon varieties (lines) were established. There were 51 materials which were classified into17 groups based on sharing the same fingerprint code, while field traits survey results showed that these plants in the same group were synonyms because of the same or similar field characters. Furthermore, DNA fingerprinting quick response (QR) codes of 471 melon varieties (lines) were constructed. Due to its fast readability and large storage capacity, QR coding melon DNA fingerprinting is in favor of read convenience and commercial applications.</p> </div

<i>o</i>‑Aryloxide-N-heterocyclic Carbenes: Efficient Synthesis of the Proligands and Their <i>p</i>‑Cymene Ruthenium Complexes

An efficient method to synthesize <i>o</i>-hydroxyaryl-substituted imidazoles (2-OH-3-R-5-^<i>t</i>BuC₆H₂)­(C₃H₃N₂) [R = ^<i>t</i>Bu (<b>1a</b>), H (<b>1b</b>)] was developed through copper-catalyzed C–N bond formation. Treatment of <b>1a</b> or <b>1b</b> with a halohydrocarbon in refluxing toluene afforded a series of <i>o</i>-hydroxyaryl imidazolinium proligands <b>2a</b>–<b>h</b> in high yields. Reactions of proligands <b>2a</b>–<b>h</b> with Ag₂O and [(<i>p</i>-cymene)­RuCl₂]₂ gave the corresponding <i>o</i>-aryloxide-N-heterocyclic carbene ligated <i>p</i>-cymene ruthenium complexes <b>3a</b>–<b>h</b>. All the imidazolium salts and ruthenium complexes were fully characterized by ¹H and ¹³C NMR spectra, elemental analysis, and high-resolution mass spectrometry. Without the cocatalyst or irradiation, these complexes can efficiently catalyze norbornene ring-opening metathesis polymerization. Notably, the structures of the catalysts were found to have significant effects on the catalytic activity and the properties of obtained polymers

UPGMA dendrogram of 471 melon accessions based on the 18 core set of SSR markers.

<p>Materials with the same fingerprinting codes had been merged. The end of each branch represents a melon variety, and many names of varieties had been omitted due to space considerations. For more detailed classification information, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0052431#pone.0052431.s001" target="_blank">Figure S1</a>. The 471 test accessions were in 3 distinct clusters: color codes red, blue, and pink.</p

Characteristics of 20 melon varieties used for developing the melon DNA fingerprinting core SSRs.

<p>Characteristics of 20 melon varieties used for developing the melon DNA fingerprinting core SSRs.</p

Materials with the same fingerprinting codes.

<p>Materials with the same fingerprinting codes.</p

Alignment of homonym melon varieties and genetic purity detection of commercial melon varieties. a.

<p>Alignment of 4 groups of homonym melon varieties. Qitian No.1, Qitian No.2, Zetian No.1 and Fengtian No.3 represent four commercial varieties in which homonym phenomena were found. Numbers to the left of colons are the numbers of varieties in Table S2; fingerprinting codes are listed to the right of the colons. <b>b.</b> Genetic purity detection results of commercial melon varieties. CV: commercial cultivar; CVH: commercial cultivar labeled “hybrid” or “F₁”; CV (thin): commercial thin rind melon cultivar; CVH (thin): commercial thin rind melon cultivar labeled “hybrid” or “F₁”; CV (thick): commercial thick rind melon cultivar; CVH (thick): commercial thick rind melon cultivar labeled “hybrid” or “F₁”.</p

Synthesis, Structures, and Norbornene ROMP Behavior of <i>o</i>-Aryloxide-N-Heterocyclic Carbene <i>p</i>-Cymene Ruthenium Complexes

Treatment of the <i>o</i>-hydroxyaryl imidazolium proligands (2-OH-3,5-^<i>t</i>Bu₂C₆H₂)­(R)­(C₃H₃N₂)⁺Br^– (R = ^<i>i</i>Pr (<b>1a</b>), ^<i>t</i>Bu (<b>1b</b>), Ph (<b>1c</b>), Mes (<b>1d</b>)) with 3 equiv of Ag₂O afforded the corresponding silver complexes <b>2a</b>–<b>d</b>. The subsequent metal-exchange reactions with [(<i>p</i>-cymene)­RuCl₂]₂ at room temperature yielded the desired <i>o</i>-aryloxide-N-heterocyclic carbene <i>p</i>-cymene ruthenium complexes <b>3a</b>–<b>d</b> in nearly quantitative yields. All the complexes were characterized by ¹H and ¹³C NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of complex <b>3b</b> was determined by single-crystal X-ray diffraction analysis. The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with <b>3a</b>–<b>d</b> was studied. Among them, complex <b>3d</b> showed high activity and efficiency toward ROMP of NBE at 85 °C without the need for any cocatalyst, and polymers with very high molecular weight (>10⁶) and narrow molecular weight distributions were obtained. This complex can also catalyze the alternating copolymerization of NBE and cyclooctene (COE)

Synthesis, Structures, and Norbornene Polymerization Behavior of Palladium Complexes Bearing Tridentate <i>o</i>‑Aryloxide-N-heterocyclic Carbene Ligands

A series of new pincer-type tridentate <i>o</i>-aryloxide-N-heterocyclic carbene ligands <b>2a</b>–<b>d</b> were synthesized. Treatment of the proligands with Ag₂O and (COD)­PdCl₂ afforded the desired <i>o</i>-aryloxide-NHC tridentate palladium complexes <b>3a</b>–<b>d</b> in high yields (NHC = N-heterocyclic carbene). In comparison with the above tridentate complexes, bidentate bis­(aryloxide-NHC) palladium complex <b>3e</b> was also synthesized. All of these complexes were fully characterized by ¹H and ¹³C NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis. The molecular structures of <b>3a</b>,<b>b</b>,<b>d</b>,<b>e</b> were determined by single-crystal X-ray diffraction analysis. On activation with either methylaluminoxane (MAO) or diethylaluminum chloride (Et₂AlCl), all palladium complexes exhibited excellent activities of up to 5.99 × 10⁷ g of PNB (mol of Pd)⁻¹ h^–1 toward norbornene addition polymerization, and the monomer conversion is up to 99.9%. Notably, the tridentate palladium complexes show better activities than the corresponding bidentate bis­(aryloxide-NHC) palladium complexes in the presence of MAO. The resulting polymers were soluble in CHCl₃ when the reactions were conducted in the presence of Et₂AlCl and were characterized by gel permeation chromatography (GPC)