Arylboron compounds have intriguing properties and are important building blocks for chemical synthesis. A family of Ir catalysts now enables the direct synthesis arylboron from aromatic hydrocarbons boranes under "solventless" conditions. The highly selective C-H activation do not interfere with subsequent in situ transformations, including Pd-mediated cross-couplings aryl halides. By virtue their favorable activities exceptional selectivities, these impart synthetic versatility reagents to...

The unusual solid-state nonplanarity seen in the X-ray structures of [N]phenylenes (an example is shown here) to be most likely result crystal-packing-induced deformations. These conclusions are based on a study published and eight new structure determinations, comparison with data napththalenes anthracenes obtained from Cambridge Structural Database, ab initio calculations.

An efficient one-pot C−H activation/borylation/oxidation protocol for the preparation of phenols is described. This method particularly attractive generation meta-substituted bearing ortho-/para-directing groups, as such substrates are difficult to access by other phenol syntheses.

Ir-catalyzed borylation of 2-substituted indoles selectively yields 7-borylated products in good yields. N-Protection, required for previous functionalizations indoles, is unnecessary.

Glandular secreting trichomes of cultivated tomato (Solanum lycopersicum) and close relatives produce a variety structurally diverse volatile non-volatile specialized ('secondary') metabolites, including terpenes, flavonoids acyl sugars. A genetic screen is described here to profile leaf trichome surface metabolite extracts nearly isogenic chromosomal substitution lines covering the genome. These contain specific regions Solanum pennellii LA0716 genome in an otherwise 'wild-type' M82...

Abstract Background For cellulosic biofuels processes, suitable characterization of the lignin remaining within cell wall and correlation quantified properties to polysaccharide enzymatic deconstruction is underrepresented in literature. This particularly true for grasses which represent a number promising bioenergy feedstocks where quantification grass lignins problematic due high fraction p- hydroxycinnamates. The main focus this work use with diverse range properties, applying multiple...

Aromatic monomer yields from lignin depolymerization can be predicted using quantifiable properties.

Glycyrrhiza uralensis (Gan-Cao), commonly called "licorice", is one of the most used herbs in traditional Chinese medicine (TCM). In United States, licorice products are often consumed as flavoring and sweetening agents food products. The triterpenoid glycyrrhizin has several biological activities, including anti-inflammatory activity. Other potential constituents G. have not been fully investigated. Airway eosinophilic inflammation a major feature allergic asthma. Eotaxin-1 (eotaxin)...

We introduce a previously unexplored parameter-halenium affinity (HalA)- as quantitative descriptor of the bond strengths various functional groups to halenium ions. The HalA scale ranks potential ion acceptors based on their ability stabilize "free ion". Alkenes in particular but other Lewis bases well, such amines, amides, carbonyls, and ether oxygen atoms, etc., have been classified scale. This indirect approach enables rapid straightforward prediction chemoselectivity for systems...

A deep investigation of amorphous V2O5-P2O5 powders for magnesium batteries communicates the vital properties to achieving superior electrochemical performance at a 75 : 25 V2O5 P2O5 molar ratio. The manipulation inter-layer spacing and amorphization can enhance Mg(2+) diffusion afford cathode with high-voltage reversibility.

A room temperature stable complex formulated as Y(NHAr*)2 has been prepared, where Ar* = 2,6-(2,4,6-(iPr)3C6H2)C6H3, by KC8 reduction of ClY(NHAr*)2. Based on EPR evidence, is an example a d1 Y(ii) with significant delocalization the unpaired electron density from metal to ligand. The isolation molecular divalent complexes challenging for rare earth elements such yttrium. In fact, stabilization state requires judicious ligand design that allows center be coordinatively saturated. Divalent...

Two plus two times two: A double cobalt-catalyzed cycloisomerization was used to convert appropriate hexaynes into hydrocarbons 1 and 2. Their X-ray structures reveal pronounced helical topologies, but their barriers enantiomerization are low compared those of the helicenes.

Six of the final cyclobutadiene rings in angular [8]phenylene and [9]phenylene (1) are closed an unprecedented cobalt-catalyzed triple cyclization appropriate nonaynes. These strained products largest known phenylenes display unusual configurational lability. Their synthesis has enabled a first estimate properties hypothetical polyheliphene.

Investigation of the methanol extract Aswagandha (Withania somnifera) roots for bioactive constituents yielded a novel withanolide sulfoxide compound (1) along with known dimer ashwagandhanolide (2) an S-linkage. The structure 1 was established by extensive NMR and MS experiments. Compound highly selective in inhibiting cyclooxygenase-2 (COX-2) enzyme 60% at 100 microm no activity against COX-1 enzyme. IC(50) values human gastric (AGS), breast (MCF-7), central nervous system (SF-268) colon...

Si29 and Al27 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy techniques were employed towards evaluation of hydrated cement paste concrete subjected to accelerated sulfate attack. Quantitative analyses the NMR spectra specimens different periods attack indicated that chain length CL SiO4/AlO4 tetrahedra was lowered by produced a significant rise in intensity ettringite sharp drop concentration monosulfate hydrate, which are some primary indications on concrete....

The plant secondary cell wall, a complex matrix composed of cellulose, hemicellulose, and lignin, is crucial for the mechanical strength water-proofing properties tissues, serves as primary source biomass biorenewable energy biomaterials. Structural analysis these polymers their interactions within wall has been heavily relying on 13C-based solid-state NMR techniques. In this study, we explore application 1H-detected techniques rapid, high-resolution structural characterization...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTotal synthesis and preliminary evaluation of (+)- ent-(-)-duocarmycin SADale L. Boger, Kozo Machiya, Donald Hertzog, Paul A. Kitos, Daniel HolmesCite this: J. Am. Chem. Soc. 1993, 115, 20, 9025–9036Publication Date (Print):October 1, 1993Publication History Published online1 May 2002Published inissue 1 October 1993https://pubs.acs.org/doi/10.1021/ja00073a019https://doi.org/10.1021/ja00073a019research-articleACS PublicationsRequest reuse...

The copper-mediated deracemization of the C2-symmetric vaulted biaryl ligands VANOL and VAPOL has been investigated. In course studies that have led to a more reliable procedure for this process, an unprecedented oxidative dimerization these uncovered. structures products were elucidated by series NMR experiments, assignments supported other spectroscopic techniques as well their chemical reactivity. This process was not observed linear BANOL BINOL, although new effective generation BINOL...

Electrophilic halofunctionalization reactions have undergone a resurgence sparked by recent discoveries in the field of catalytic asymmetric halocyclizations. To build mechanistic understanding these transformations, toolbox analytical methods has been deployed, addressing roles catalyst, electrophile (halenium donor), and nucleophile determining rates stereopreferences. The test reaction, (DHQD)2PHAL-catalyzed chlorocyclization 4-arylpent-4-enoic acid with 1,3-dichloro-5,5-dimethylhydantoin...

In recent work to develop cyanine dyes with especially large Stokes shifts, we encountered a "blueing" reaction, in which the heptamethine dye Cy7 (IUPAC: 1,3,3-trimethyl-2-((1E,3E,5E)-7-((E)-1,3,3-trimethylindolin-2-ylidene)hepta-1,3,5-trien-1-yl)-3H-indol-1-ium) undergoes shortening two-carbon steps form pentamethine (Cy5) and trimethine (Cy3) analogs. Each step blue-shifts resulting absorbance wavelength by ca. 100 nm. Though photochemical oxidative chain-shortening reactions had been...

A one-pot protocol for converting 1,3- and 1,4-substituted aryl halides to arylamine boronate esters is described. This achieved by sequential Ir-catalyzed aromatic borylation at the least hindered C−H bond of halide subsequent Pd-catalyzed C−N coupling position crude arylboronic ester.

"Weakly coordinating anions" such as tetraarylborates are ubiquitous in applications of inorganic and organometallic chemistry, with great industrial importance. In this work, we probe the ion-pairing ability these weakly anions using highly sensitive chromium(VI) nitrido bis(diisopropylamido) system NCr(N-i-Pr2)2X, one variable coordination site (X). This is being used quantification ligand donor to high-valent metal centers has simply been called parameter (LDP). The can be measured by...

Sechs der Cyclobutadienringe im gewinkelten [8]Phenylen und [9]Phenylen 1 entstehen bei neuartigen Cobalt-katalysierten dreifachen Cyclisierung geeigneter Nonaine. Diese gespannten Produkte sind die größten bekannten Phenylene konfigurativ ungewöhnlich labil. Ihre Synthese ermöglichte eine erste Abschätzung Eigenschaften des hypothetischen Polyheliphens.