Synthesis and Characterization of a 1,3-Phenylene-Bridged N‑Alkyl Bis(benzimidazole) CCC-NHC Pincer Ligand Precursor: Homobimetallic Silver and Rhodium Complexes and the Catalytic Hydrosilylation of Phenylacetylene

A new CCC-NHC pincer ligand precursor architecture based on 1,3-bis­(N-alkylbenzimidazole)­benzene has been synthesized and metalated using Ag₂O, forming a homobimetallic Ag complex with a metal to ligand ratio of 1:1. The Ag complex was treated with either [Rh­(COD)­Cl]₂ or Rh­(COD)₂OTf and NBu₄I to yield a homobimetallic Rh complex by transmetalation. The Rh complexes were characterized, and an X-ray structure is reported. Their catalytic activity in the hydrosilylation of phenylacetylene is reported

Synthesis, Characterization, and X‑ray Molecular Structure of Tantalum CCC-N-Heterocyclic Carbene (CCC-NHC) Pincer Complexes with Imidazole- and Triazole-Based Ligands

Unprecedented Ta bis­(NHC) pincer complexes have been synthesized and characterized by extension of the early-transition-metal amido methodology. The reaction of 1,3-bis­(3-butylimidazol-1-yl)­benzene diiodide (<b>1</b>) with stoichiometric and substoichiometric amounts of (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V) yielded (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­diiodotantalum­(V) (<b>2</b>) and (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>3</b>). Use of excess (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V) to metalate 1,3-bis­(3-butylimidazol-1-yl)­benzene diiodide (<b>1</b>) yielded (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>3</b>) exclusively. Furthermore, the first early-transition-metal (group 3–5) triazole-based NHC complex, (1,3-bis­(3-butyltriazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>5</b>), has been synthesized via amine elimination of 1,3-bis­(3-butyltriazol-1-yl)­benzene diiodide (<b>4</b>) with (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V)

Synthesis, Characterization, and X‑ray Molecular Structure of Tantalum CCC-N-Heterocyclic Carbene (CCC-NHC) Pincer Complexes with Imidazole- and Triazole-Based Ligands

Unprecedented Ta bis­(NHC) pincer complexes have been synthesized and characterized by extension of the early-transition-metal amido methodology. The reaction of 1,3-bis­(3-butylimidazol-1-yl)­benzene diiodide (<b>1</b>) with stoichiometric and substoichiometric amounts of (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V) yielded (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­diiodotantalum­(V) (<b>2</b>) and (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>3</b>). Use of excess (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V) to metalate 1,3-bis­(3-butylimidazol-1-yl)­benzene diiodide (<b>1</b>) yielded (1,3-bis­(3-butylimidazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>3</b>) exclusively. Furthermore, the first early-transition-metal (group 3–5) triazole-based NHC complex, (1,3-bis­(3-butyltriazol-1-yl-2-idene)-2-phenylene)­(<i>tert</i>-butylimido)­(dimethylamido)­iodotantalum­(V) (<b>5</b>), has been synthesized via amine elimination of 1,3-bis­(3-butyltriazol-1-yl)­benzene diiodide (<b>4</b>) with (<i>tert</i>-butylimido)­tris­(dimethylamido)­tantalum­(V)

Phase solubility diagram of PA and <i>β</i>-CD at 25, 35°C (n = 3).

<p>Phase solubility diagram of PA and <i>β</i>-CD at 25, 35°C (n = 3).</p

Lowest energy PA-<i>β</i>-CD docked complex.

<p>(A) Stick model. (B) The optimized model. Yellow stick represents <i>β</i>-CD and grey small molecule represents PA.</p

Characterization of PA, <i>β</i>-CD, PA/CD CI, and PA/CD PM.

<p>(A) DSC thermograms. (B) IR spectra. (C) 6 PXRD patterns. (D) SEM spectra.</p

Degradation profiles of PA-CD inclusion complex (a, c, e) and PA (b, d, f).

<p>Thermal stability (a, b), humidity stability (c,d), and photostability (e,f).</p

Chemical structures of (A) PA and (B) <i>β</i>-cyclodextrin.

<p>Chemical structures of (A) PA and (B) <i>β</i>-cyclodextrin.</p

<i>Neocosmospora</i> sp.-Derived Resorcylic Acid Lactones with in Vitro Binding Affinity for Human Opioid and Cannabinoid Receptors

Bioassay-guided fractionation of a fungus <i>Neocosmospora</i> sp. (UM-031509) resulted in the isolation of three new resorcylic acid lactones, neocosmosin A (<b>2</b>), neocosmosin B (<b>3</b>), and neocosmosin C (<b>4</b>). Three known resorcylic acid lactones, monocillin IV (<b>1</b>), monocillin II (<b>5</b>), and radicicol (<b>6</b>), were also isolated and identified. The structures of these compounds were established on the basis of extensive 1D and 2D NMR spectroscopic analysis, mass spectrometric (ESIMS) data, and X-ray crystallography. Compounds <b>4</b>–<b>6</b> show good binding affinity for the human opioid receptors. These findings have important implications for evaluating the potential psychoactive effects with this class of compounds

UPLC-MS-ELSD-PDA as a Powerful Dereplication Tool to Facilitate Compound Identification from Small-Molecule Natural Product Libraries

The generation of natural product libraries containing column fractions, each with only a few small molecules, using a high-throughput, automated fractionation system, has made it possible to implement an improved dereplication strategy for selection and prioritization of leads in a natural product discovery program. Analysis of databased UPLC-MS-ELSD-PDA information of three leads from a biological screen employing the ependymoma cell line EphB2-EPD generated details on the possible structures of active compounds present. The procedure allows the rapid identification of known compounds and guides the isolation of unknown compounds of interest. Three previously known flavanone-type compounds, homoeriodictyol (<b>1</b>), hesperetin (<b>2</b>), and sterubin (<b>3</b>), were identified in a selected fraction derived from the leaves of <i>Eriodictyon angustifolium</i>. The lignan compound deoxypodophyllotoxin (<b>8</b>) was confirmed to be an active constituent in two lead fractions derived from the bark and leaves of <i>Thuja occidentalis</i>. In addition, two new but inactive labdane-type diterpenoids with an uncommon triol side chain were also identified as coexisting with deoxypodophyllotoxin in a lead fraction from the bark of <i>T. occidentalis.</i> Both diterpenoids were isolated in acetylated form, and their structures were determined as 14<i>S</i>,15-diacetoxy-13<i>R</i>-hydroxylabd-8­(17)-en-19-oic acid (<b>9</b>) and 14<i>R</i>,15-diacetoxy-13<i>S</i>-hydroxylabd-8­(17)-en-19-oic acid (<b>10</b>), respectively, by spectroscopic data interpretation and X-ray crystallography. This work demonstrates that a UPLC-MS-ELSD-PDA database produced during fractionation may be used as a powerful dereplication tool to facilitate compound identification from chromatographically tractable small-molecule natural product libraries