AuI-Catalyzed Haloalkynylation of Alkenes

The formal insertion of alkenes into aromatic chloro- and bromoalkynes takes place under cationic gold catalysis. This haloalkynylation reaction can be performed with cyclic, gem-disubstituted and monosubstituted alkenes, using BINAP, triazolo[4,3-b]isoquinolin-3-ylidene ligands or SPhos, respectively. The products were isolated in moderate to excellent yields and with complete diastereo- and regioselectivity; the halogen atom bonding the more substituted carbon of the alkene. Preliminary experiments showed that the enantioselective haloalkynylation of cyclopentene can be performed with (S)-BINAP to afford the insertion products with moderate to good enantioselectivities.     

Synthesis of Polysubstituted Iodoarenes Enabled by Iterative Iodine‐Directed para and ortho C−H Functionalization

Among halogenated aromatics, iodoarenes are unique in their ability to produce the bench‐stable halogen(III) form. Earlier, such iodine(III) centers were shown to enable C?H functionalization ortho to iodine via halogen‐centered rearrangement. The broader implications of this phenomenon are explored by testing the extent of an unusual iodane‐directed para C?H benzylation, as well as by developing an efficient C?H coupling with sulfonyl‐substituted allylic silanes. Through the combination of the one‐shot nature of the coupling event and the iodine retention, multisubstituted arenes can be prepared by sequentially engaging up to three aromatic C?H sites. This type of iodine‐based iterative synthesis will serve as a tool for the formation of value‐added aromatic cores.     

Different approaches to proximate analysis by thermogravimetry analysis

The experimental optimization by the simplex method of the proximate analysis of coal and biomass by thermogravimetry analysis (TGA) is reported. Heating rate, final temperature, holding time, Ar flow rate and sample size were the control variables. The response function used was chosen to minimize the difference in percentage of volatile matter with the ASTM characterization. The relative accuracy of the method was demonstrated by determination of the volatile matter contents of a number of coals in parallel with the ASTM certified method. The method is successfully used with biomass samples.     

Facile preparation of 3-substituted 2-quinazolinones via electrogenerated base

A new series of 3,4-disubstituted quinazolin-2-ones, with potential T-type calcium channel antagonist activity, and new 4-methylene-quinazolin-2-ones, promising catalysts as N-heterocyclic olefins, have been prepared in good yield by a simple reaction between 2-aminobenzophenone, or 2-aminoacetophenone, and cyanomethyl anion electrogenerated by acetonitrile reduction at a graphite electrode, followed by the addition of different organic isocyanates and subsequent heterocyclization.     

Stepwise cycloreversion of oxetane radical cations with initial C-O bond cleavage

2,4,6-Triaryl(thia)pyrylium salts have been used as electron-transfer photosensitizers for the cycloreversion of the oxetane ring system. The radical cation of 2,3-diphenyl-4-hydroxymethyloxetane (1) undergoes stepwise splitting via initial O-C2 cleavage. Spin and charge in the resulting intermediate are located in the oxygen and carbon atoms, respectively. Subsequent intramolecular nucleophilic attack produces 2,3-diphenyl-4-hydroxytetrahydrofuran (4a). Formation of this product occurs in the submicrosecond time scale, competing with C3-C4 cleavage to the detectable (lambdamax = 470 nm) trans-stilbene radical cation.     

Simultaneous detection of molecular weight and activity of adenylate kinases after electrophoretic separation

Adenylate kinases (AKs) are ubiquitous monomeric phosphotransferases catalyzing the reversible reaction, AMP + MgATP = ADP + MgADP, which plays a pivotal role in the energetic metabolism. In vertebrates, six AK isoforms are known. In this work, we report the detection of many AK isoforms directly on gel or NC after separation by denaturing electrophoresis and electroblotting, by an optimized protocol for the enzyme detection. The method allows to clarify the apparent MW of most of those AK isozymes that follow the cited reaction, especially onto NC where bands are sharper due to the absence of protein diffusion. In contrast, GTP:AMP phosphotransferases are not detectable. AK activity from many sources can be detected in both its reaction courses; ATP production appears as dark-blue bands, while ADP formation appears as nonfluorescent bands over a fluorescent background, under long-wavelength UV light. We show that nondenaturing gel electrophoresis is not the first choice for AK activity detection. Our method is different from the preceding reports on AK activity detection in bacteria after native polyacrylamide gel separations, in the absence of SDS or methanol. The procedure is also quantitative, allowing to determine the amount of enzyme present in samples.     

Vascular endothelial and smooth muscle cell culture on NaOH-treated poly(epsilon-caprolactone) films: a preliminary study for vascular graft development

Tissue engineering offers the potential of providing vessels that can be used to replace diseased and damaged native blood vessels. The endothelization of a synthetic vascular graft minimizes the failures associated with blood clotting and platelet activation. The aim of this study was to culture vascular-derived endothelial and smooth muscle cells on both untreated and NaOH-treated poly(epsilon-caprolactone) (PCL) films, a biocompatible and bio-resorbable polymer, and to evaluate the behavior of both cell types as a preliminary study for vascular graft development. PCL films were prepared by hot pressing; characterized by DSC, IR, SEM, and scanning force microscopy; and treated with NaOH to increase the surface hydrophilicity before cell culture. Endothelial and smooth muscle cells, isolated from pig cava vein, were characterized by immunofluorescence and confocal microscopy studies of endothelial nitric oxide synthase and alpha-smooth muscle actin. Good adhesion, growth, viability and morphology of both the endothelial and smooth muscle cells on PCL films were obtained, but a light stimulation of mitochondrial activity was observed during short culture times. NaOH treatment improved the adhesion and enhanced the proliferation in both cell types. This verified the possible use of this modified polymer as a support in the preparation of a synthetic vascular graft. [Diagram: see text] SEM micrograph of smooth muscle cells cultured on NaOH-treated PCL film. (Original magnification: 1000x).     

Polyhydroxylated pyrrolizidines. Part 6: A new and concise stereoselective synthesis of (+)-casuarine and its 6,7-diepi isomer, from DMDP

A new synthesis for (+)-casuarine (1) and its 6,7-diepi isomer (15) in a stereocontrolled manner, is reported herein. An appropriately protected polyhydroxylated pyrrolidine, such as (2R,3R,4R,5R)-3,4-dibenzyloxy-2′-O-tert-butyldiphenylsilyl-2,5-bis(hydroxymethyl)pyrrolidine (3, protected DMDP), easily available from d-fructose, was chosen as the chiral starting material. Compounds 1 and 15 were obtained from 3, in seven steps, in a 23.2 and 20.5% overall yields, respectively.     

Conformational study of N-substituted 8-azabicyclo[3.2.1]octan-3-ones

N-Substituted 8-azabicyclo[3.2.1]octan-3-ones have been studied by ¹H and ¹³C NMR spectroscopy. In CDCl₃ solutions, these ketones display the same preferred conformation. The pyrrolidine and piperidone rings adopt a flattened N-8 envelope and distorted chair conformation, puckered at N-8 and flattened at C-3, respectively, with the N-substituent in axial position with respect to the piperidone ring.     

Potentiometric dissociation constants and analytical properties of α-mercaptobenzeneacetic acid

The α-mercaptobenzeneacetic acid has been synthesized and screened for its properties as an analytical reagent. The acid dissociation constants have been determined potentiometrically in 0.1 M KNO₃ and 0.5 M KNO₃ ethanol-water 20% (v/v) solutions at 25 ± 0.1 °C.