Cyclohexenones as Michael acceptors in the Staunton-Weinreb annulation: a simple stannane modification for the synthesis of polycyclic systems

[reaction: see text] o-Toluate anions generated via transmetalation from the corresponding tributyl stannane underwent a Michael addition-Dieckmann condensation sequence with various cyclohexenones. This protocol provides an efficient entry into complex polycyclic systems without the use of beta-alkoxy enones hitherto required for the reaction.     

Cascade annulation of malonic diamides: a concise synthesis of polycyclic pyrroloindolines

A concise synthesis of polycyclic pyrroloindolines from simple malonic diamides via an intramolecular oxidative coupling/condensative cyclization cascade process is reported. The reaction provides an efficient method to construct polycyclic pyrroloindolines in good to excellent yields, which should be useful in the synthesis of natural products and pharmaceutical molecules.     

Synthesis of fused polycyclic aromatics by palladium-catalyzed annulation of arynes using 2-halobiaryls

The Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides provides a very efficient, high yielding synthesis of polycyclic aromatic and heteroaromatic hydrocarbons. This process appears to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.     

Selective cleavage of polycyclic cyclopropanes by electrochemical oxidation

Anodic oxidation in acetic acid of polycyclic cyclopropanes, namely tricyclene, cyclofenchene, and longicyclene, followed by hydrolysis brought about stereo- and regioselective formation of the corresponding homoallylic alcohols as the main product in good yields.     

Ionic liquid-promoted regiospecific Friedlander annulation: novel synthesis of quinolines and fused polycyclic quinolines

Several room-temperature ionic liquids (ILs) based on 1-butylimidazolium salts with varying anions were synthesized and evaluated for the preparation of biologically active substituted quinolines and fused polycyclic quinolines using the Friedlander heteroannulation reaction. On screening, 1-butylimidazolium tetrafluoroborate [Hbim]BF4 was found to be the best ionic liquid for the heteroannulation reaction, and the reasons to this effect are well explained. The reactions proceed very well under relatively mild conditions without any added catalyst. The IL acts as a promoter for this regiospecific synthesis and can be recycled. By this green approach, various quinolines were prepared in excellent yields and purity and well-characterized.     

Fluorescent sensors for nitroaromatic compounds based on monolayer assembly of polycyclic aromatics

A class of fluorescent films in which pyrene was assembled, in a monolayer manner, on glass slide surfaces via various flexible spacers of different lengths and substructures was used for the detection of nitroaromatic compounds (NACs) in vapor phase. This design strategy offers several advantages for thin film fluorescent sensory materials. These advantages have been demonstrated experimentally by the sensitive response of the films to the presence of trace amounts of NACs in vapor phase. The fluorescence quenching of the films upon exposure to NACs vapors depends on several factors, including the evaporate rate of the NAC detected, the length of the spacers connecting the sensing element and the substrate surface, and the density of the sensing element on the substrate surface. Further experimentation showed that the sensing process is reversible and free of commonly encountered interference. The sensitive response, reversibility of the sensing process, and freedom from commonly encountered interference of the specially designed films to NACs qualify these materials as promising NACs fluorescent sensory materials.     

Highly efficient route to fused polycyclic aromatics via palladium-catalyzed aryne annulation by aryl halides

Polycyclic aromatic and heteroaromatic hydrocarbons have been synthesized in high yield by two different processes involving the Pd-catalyzed annulation of arynes. The first process involves a Pd-catalyzed annulation of arynes by 2-halobiaryls and related vinylic halides. The second process utilizes a Pd-catalyzed double annulation of arynes by simple aryl halides. Both processes appear to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.     

An expedient domino three-component [3+2]-cycloaddition/annulation protocol: regio- and stereoselective assembly of novel polycyclic hybrid heterocycles with five contiguous stereocentres

A novel three-component strategy for the efficient synthesis of unprecedented polycyclic hybrid heterocycles comprising fused, bridged, and spiro rings with five contiguous stereocentres in a regio- and stereoselective manner is described. This transformation proceeds via 1,3-dipolar cycloaddition of azomethine ylides generated in situ from the reaction of sarcosine/thiazolidine-4-carboxylic acid and acenaphthoquinone to a series of 2-[arylmethylidene]-3,4-dihydro-1(2H)-acridinones and concomitant annulation through an intramolecular aldol-type reaction.     

An ultrasensitive electrochemical sensor for the mercuric ion via controlled assembly of SWCNTs

An ultrasensitive "turn-on" electrochemical sensor for the Hg(2+) ion was proposed based on the T-Hg(2+)-T coordination chemistry and the controlled assembly of SWCNTs on the MHA/SAM-modified gold electrode.     

New polycyclic pyran ring systems

Reaction of 1-oxo-3-dialkylamino-1H-naphtho[2,1-b]pyrans, 4-hydroxycoumarin and formaldehyde gave rise to the formation of 1-oxo-2-((2-oxo-4′-hydroxy-2′H-1′-benzopyran-3′-yl)-melhyl J-3-dialkylamino-1H-naphtho[2,1-b]pyrans. When these compounds were refluxed in glacial acetic acid, cyclization occurred and 6,8-dioxo-6H,7H,07-,5,15,16-trioxadibenzo[a,j]-naphthacene arose by cleavage of the dialkylamino group. In a similar manner, starting from suitable products, many other trioxanaphthacene or azadioxanaphthacene derivatives were synthesized.     

Microchip-based electrochemical detection for monitoring cellular systems

The use of microchip devices to study cellular systems is a rapidly growing research area. There are numerous advantages of using on-chip integrated electrodes to monitor various cellular processes. The purpose of this review is to give examples of advancements in microchip-based cellular analysis, specifically where electrochemistry is used for the detection scheme. These examples include on-chip detection of single-cell quantal exocytosis, electrochemical analysis of intracellular contents, the ability to integrate cell culture/immobilization with electrochemistry, and the use of integrated electrodes to ensure cell confluency in longer-term cell culture experiments. A perspective on future trends in this area is also given.     

A non-covalent strategy for the assembly of supramolecular photocurrent-generating systems

Three photocurrent-generating thin films were assembled on gold surfaces. SAM I was constructed from molecules consisting of an alkyl disulfide group linked covalently to a 12-residue helical peptide and terminated with an alanine residue containing a pyrene chromophore. SAM I served as a benchmark for multilayered films II and III in photocurrent generation experiments. Films II and III were assembled from several components that were linked noncovalently by metal-ligand complexation. Cyclic voltammetry and contact angle measurements suggest that the films consist of ordered layers with relatively few defects. Photoexcitation of SAM I by the output of a 350 nm lamp ( approximately 0.2 mW power incident on the sample) results in current generation in the range 5-10 nA/cm2. Photoexcitation of II and III yields higher current in the range 10-30 nA/cm2, representing a quantum efficiency of approximately 1%. The observation of comparable or higher current from noncovalently assembled multicomponent films indicates that this method of assembly may obviate the problems associated with the covalent assembly of devices from large molecules.     

Concise assembly of the polycyclic frameworks associated with the hapalindole and fischerindole alkaloids

[reaction: see text] Reaction of N-methylindole (4) with 6,6-dibromobicyclo[3.1.0]hexane (5) in the presence of silver tetrafluoroborate affords conjugate 7 in 67% yield. This product can be readily elaborated to compounds 12b and 13b which embody the polycyclic frameworks associated with members of the hapalindole and fischerindole classes of alkaloids. The chiral-auxiliary-substituted 6,6-dibromobicyclo[3.1.0]hexanes 21 and 22 react with indole to give adducts likely to be useful in the enantioselective total synthesis of the title alkaloids.     

Mass-transfer problems in the electrochemical systems

The problems concerning quantitative analysis of mass-transfer processes in the electrochemical systems (ECS) are briefly reviewed. The interrelation between the mass-transfer problems in the electrochemical and heat systems is considered. Various approaches to the numerical determination of distributions of concentrations of ions of all types and electrochemical potential in the ECS are considered. The methods of allowance for the migration transfer and choosing the boundary conditions for the transfer equations and other problems are considered. Some actual lines of development of the theory of mass-transfer in the ECS are pointed out.     

Microbe-based electrochemical sensing systems

The combination of micro-organisms with electrochemical sensors can result in new sensing systems with extended analytical capabilities. The most common approaches for this combination are microbial electrodes and microbiological assays which utilize electrochemical detection.     

Domino Mukaiyama-Michael reactions in the synthesis of polycyclic systems

Good results were obtained in the Mukaiyama-Michael reaction of the silyl enol ether of cyclohexanone with 2-methyl-2-cyclopentenone and carvone, with transfer of the silyl group to the receiving enone and with TrSbCl₆ as catalyst. A second Mukaiyama-Michael reaction of this new silyl enol ether with methyl vinyl ketone and cyclization of the resulting adduct leads to tricyclic compounds in one-pot domino sequences. The scope and limitations of this domino reaction have been investigated.     

Gold-catalyzed assembly of heterobicyclic systems

We have described an efficient gold-catalyzed double cyclization of 1,5-enynes to afford a range of heterobicyclic compounds, including oxabicylclo[3.2.1]octenes, azabicyclo[3.2.1]octenes, oxaspiro[5.4]decene, azaspiro[5.4]decene, oxaspiro[5.5]undecene, oxabicyclo[4.3.0]nonene, azabicyclo[4.3.0]nonene, and oxabicyclo[4.4.0]decene. The mechanism of this reaction is proposed to involve a chemoselective gold-based alkyne activation, carbocyclization, intramolecular nucleophilic addition, followed by protodemetalation. The most notable aspect of this process is the efficient and diastereospecific interception of the reactive intermediate of the initial 6-endo-dig (or 5-endo-dig) cyclization with either oxygen- or nitrogen-based nucleophiles.     

Dienyne RCM/Diels-Alder approach for the construction of novel steroid-like polycyclic systems

Our studies directed towards the preparation of novel steroid-like derivatives using RCM reactions are described. The strategy here described was applied to the construction of novel ring-inserted skeleton-expanded steroid analogs by combination of tandem ring-closing metathesis of lineal dienynes and Diels-Alder reaction.     

Three-dimensionally printed electrochemical systems for biomedical analytical applications

Additive manufacturing (3D-printing) has revolutionized many areas of the manufacturing. Three-dimensional printing offers enormous potential to biomedical devices, including electroanalytical systems. The motivation for 3D printing is rapid prototyping and decentralized customizable fabrication of bioanalytical systems in the diverse and remote areas of the globe. We overview the recent trends and discuss the fabrication and applications of 3D printed polymer/carbon and metal electrodes and whole electrochemical systems for biomedical applications and DNA detection. We show that sky is the limit and envision whole analytical systems, including electronics, to be 3D printed in the future for diagnostics in the remote areas of the globe.