BH3-catalyzed oligomerization of ethyl diazoacetate: the role of C-boron enolates

In contrast to trialkyl boranes, the reaction of borane (BH3) and ethyl diazoacetate (EDA) generates dimer, trimer, and oligomers of EDA. The products arise from double, triple, and multiple insertions of CHCO2Et groups in B-C bonds. On the basis of NMR spectroscopic data, trapping experiments, and computational studies, a novel C-boron enolate has been identified as a key intermediate in this reaction. This C-boron enolate species is calculated to be 7.1 kcal/mol (gas phase) more stable than its isomeric O-boron enolate form. Both spectroscopic data and trapping results also reveal the formation of a doubly borylated enolate generated as a side product by a proton transfer between the C- and O-boron monoenolates.     

An approach to the synthesis of stenine

A type 2 N-acylnitroso intramolecular Diels-Alder reaction followed by reductive N-O bond cleavage formed the B and C rings of the Stemona alkaloid stenine. Further elaboration provided the functionalized tricyclic core.     

Simple and Sensitive Electrochemical DNA Detection of Primer Generation‐Rolling Circle Amplification

A new electrochemical sequence‐specific DNA detection platform based on primer generation‐rolling circle amplification (PG‐RCA), methylene blue (MB) redox indicator, and indium tin oxide (ITO) electrode is reported. In the presence of a specific target sequence, PG‐RCA, an isothermal DNA amplification technique, produced large amounts of amplicons in an exponential manner. In addition to the standard components, the reaction mixture contained MB, which bound with the PG‐RCA amplicons. End‐point electrochemical measurement by differential pulse voltammetry (DPV) was performed using ITO electrode. The amplicon‐bound MB resulted in a lower DPV signal than free MB due to a smaller diffusion coefficient as well as electrostatic repulsion between the negatively charged amplicon‐bound MB and ITO electrode. With simple assay design (recognition probe) and instrumentation (operating temperature at 37 °C and ITO electrode without the need for probe immobilization), this detection platform is well suited for point‐of‐care and on‐site testing. Real‐time measurement was also achieved by pretreating the ITO electrode with bovine serum albumin.     

Phase transfer catalysts anchored to polystyrene

Quarternary phosphonium and ammonium salts attached to polystyrene resins by short (2 - 3 atom) carbon chains are highly active phase transfer catalysts for a variety of nucleophilic substitution reactions.     

Adsorption of PTCDI on Au(1 1 1): Photoemission and scanning tunnelling microscopy

The adsorption of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI) on Au(1 1 1) has been studied using synchrotron-based X-ray photoelectron spectroscopy and in situ scanning tunnelling microscopy. Direct topographic and surface coverage information provided by the scanning probe measurements have enabled us to correlate peaks in the relatively complex carbon core-level photoemission to interactions of the surface with different parts of the PTCDI molecule. A strong interaction between the imide ends of the molecule with the underlying gold substrate is evidenced by a large chemical shift in the imide carbon peaks, which is observed only for the first adsorbed layer.     

Regioselective SNAr reactions of substituted difluorobenzene derivatives: practical synthesis of fluoroaryl ethers and substituted resorcinols

In this Letter, we describe a practical and highly selective method for the preparation of fluoroaryl ethers and differentially substituted resorcinol derivatives. This synthetic strategy relies on a selective S_NAr of substituted difluorobenzene derivatives with various alcohols.     

Admissible convergence for the Poisson-Szegö integrals

We prove almost everywhere semirestricted admissible convergence of the Poisson-Szegö integrals ofL ^p functions (1 <p ≤ ∞) on the Bergman-Shilov boundary of a Siegel domain. In the case of symmetric domains our theorem can be deduced from the results by Peter Sjögren on admissible convergence to the boundary of Poisson integrals on symmetric spaces, although semirestricted admissible convergence means here a more general approach to the boundary then originally defined for symmetric spaces.     

Novel trifunctional building blocks for fluorescent polymers

[reaction: see text] Herein, we describe the synthesis of fluorescent 2-(arylsulfonyl)methacrylates and its polymers. These novel trifunctional monomers, possessing a fluorescent arylsulfonyl (ArSO(2)) group, an alkyl group (R), and a polymerizable olefin, serve as useful building blocks for functionalized fluorescent polymers.     

Enantiomeric and isomeric separation of herbicides using cyclodextrin-modified capillary zone electrophoresis

Cyclodextrin-modified capillary zone electrophoresis (CD-CZE) was applied successfully to the enantiomeric and isomeric separation of three herbicides (imazaquin, diclofop and imazamethabenz). Commercially available cyclodextrins were evaluated for separation of the enantiomers and isomers of the three herbicides having varied molecular structures. The enantiomers of imazaquin and diclofop, and the isomers of imazamethabenz could be resolved with a resolution of ≥1.5. The resolution was found to depend on pH of the run buffer, cyclodextrin type and cyclodextrin concentration. By employing mixed cyclodextrins in the running buffer, the three herbicides were simultaneously separated in a single run. In addition, rapid (less than 3 min) enantiomeric separation is demonstrated using imazaquin as a model herbicide. The reported capillary electrophoresis (CE) methods are simple, rapid, efficient and reproducible and our results demonstrate that CE provides a powerful analytical tool for enantiomeric and isomeric separation of herbicides.