Garratt–Braverman cyclization on basic alumina: a green protocol with improved selectivity

A green protocol (compared to the existing methodology) for carrying out Garratt–Braverman cyclization has been developed. The method involves stirring a pre-absorbed bispropargyl sulfone/ether/sulfonamide over basic alumina. The reaction with sulfones was over within 10–15 min at room temperature whereas for the ether/sulfonamide the reaction took 6–8 h at 130 °C. The products, aryl naphthalene derivatives, are obtained by simple filtration through Celite, in excellent yields.     

A facile convergent route to dendritic polyols

The synthesis of monodisperse dendrimers triggers a great challenge to the synthetic chemistry. Here, we reported a facile convergent approach to the synthesis of the first generation, six-directional ether-bond polyols with better controlled structures and ease of purification.     

An interesting competition between 6π-electro- and Garratt–Braverman cyclization in bis-diene-allene sulfones: synergy between experiment and theory

The reactivity of a series of bispropargyl sulfones with an ortho alkenyl moiety was studied. Under basic condition, these molecules isomerized to the bis-diene-allene system capable of undergoing 6π-electro-(EC) as well as Garratt–Braverman (GB) cyclization. The reaction generally favours the GB process but the balance can be tilted towards the 6π-EC pathway by suitable perturbation of structure and temperature. The findings are useful as the systems undergoing GB pathway can show DNA-damage activities.     

A facile route to growth of γ-MnOOH nanorods and electrochemical capacitance properties

Single crystal nanorods of γ-MnOOH with lengths up to hundreds of nanometers were successfully prepared employing a novel solvothermal process based on the redox reaction between potassium permanganate (KMnO(4)) and N, N-dimethyl ammonium formate (DMF) without extra surfactant or template. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Fourier transformed infrared spectroscopy (FTIR). The electrochemical properties of γ-MnOOH nanorods were investigated by cyclic voltammetry and galvanostatic charge-discharge performance measurements. Specific capacitance (C(s)) calculated from the galvanostatic discharge curve was 131.9 F g(-1) for γ-MnOOH nanorods at the current density of 0.5 A g(-1). The electrochemical experiment results demonstrate that γ-MnOOH nanorods should be a good candidate as electrode material for supercapacitor.     

A facile route to polysubstituted 2-hydroxy-3-nitro-cyclopentanones via a linear α-ketoenamine

The morpholino monoenamine of diacetyl has been synthesized and reacted with conjugated nitroolefins to give functionalized cyclopentanone derivatives, after hydrolysis of the isolated enamine intermediates.     

A facile pathway to 2-furfurylketones

2-(Chloromethyl)furan as an electrophile reacted with lithium trialkylalkyllylbo-rates,followcl by the oxidation with H_2O_2 under basic condition to afford 2-furfurylketonesin good yields.This provides a new method for the preparation of 2-furfurylkctoncs.     

Self-catalytic Michael reaction of enolizable carbonyl compounds. A facile route to α-methylene-δ-valerolactones

Various dicyclohexylammonium 2-phosphono-5-oxoalkanoates 3 were prepared by the Michael reaction of enolizable carbonyl compounds with the acrylate 1. The corresponding 2-phosphono-5-oxoalkanoic acids 4 were converted into α-phosphono-δ-valerolactones 6. The products were shown to be useful substrates for the synthesis of α-methylene-δ-valerolactones 7 by the Horner-Wadsworth-Emmons reaction.     

A furan route to (−)-exo-isobrevicomin

A new enantiocontrolled synthesis of (−)-exo-isobrevicomin, isolated from male mountain pine beetles, Dendroctonus ponderosae, has been established starting from 5-ethyl-2-furfural by employing AD-mix-induced asymmetric induction and oxidative furan ring-expansion reaction as the key steps.     

Reactivity of Bispropargyl Sulfones under Basic Conditions: Interplay Between Garratt–Braverman and Schmittel/Myers–Saito Cyclization Pathway

The preference for Garratt–Braverman (GB) over Myers–Saito (MS) and Schmittel (SCM) cyclizations has recently been demonstrated in sulfones capable of undergoing all three of the processes. As the GB cyclization is a self-quenching process, there is a need to change the selectivity to the non-self-quenching MS or SCM pathway so as to enhance the DNA-cleaving efficiency that operates through the radical-mediated process. Herein we report a conformational constraint-based strategy developed by using computations (M06-2X/6-31+G*) to switch the selectivity from GB to MS/SCM pathway which also results in greater DNA-cleavage activity. The preference for GB could be brought back by easing the constraint with the help of spacers.     

Highly diastereoselective radical addition–cyclization strategy: facile synthesis of substituted furans

A novel strategy is described in which an intermolecular carbon-centered radical addition to a β-oxygenated acceptor followed by intramolecular cyclization leads to the formation of 2,3,4- and 2,3,4,5-substituted furan rings. Excellent levels of 2,4-trans selectivity are observed in accordance with the Beckwith–Houk model for selectivity in 5-exo radical cyclizations.     

Ni–Zn ferrite-loaded superparamagnetic amorphous carbon nanotubes through a facile route

Partial filling of mixed ferrite (Ni_0.5Zn_0.5Fe₂O₄; NZFO) nanoparticles into the amorphous carbon nanotubes (aCNTs) cavity is achieved by simple mixing of the aqueous dispersions of the two (aCNTs and NZFO) at room temperature. The process of incorporation of the nanoparticles into the aCNT cavity is solely mediated by the capillary action of the liquid. NZFO nanoparticles were homogeneously dispersed in the aqueous solution but after mixing they are sparsely distributed into the aCNT channel as a result of the capillary action. The encapsulation of the nanoparticles into the aCNTs amorphous shield was established by means of X-ray diffraction, transmission electron microscopy, Fourier transformed infrared spectroscopy, and Raman spectroscopic analysis. Such entrapment of the nanoparticles causes the composite nanotubes superparamagnetic in nature with blocking temperature (T _B) at 15 K. However, compared to the powder NZFO nanoparticles, T _B appears more sharply and at relatively lower temperature. Low filling density and the spatial confinement of the nanoparticles lessen the inter-particle interactions and the polydispersity within the NZFO nanoparticles which are manifested in their altered magnetic behavior.     

A versatile route to the synthesis of 1-substituted β-carbolines by a single step Pictet-Spengler cyclization

A one-step conversion of l-tryptophan and activated aldehydes (1,2-dicarbonyl compounds) directly to 1-substituted β-carbolines without formation of the tetrahydro derivatives under modified Pictet-Spengler conditions was described. Moreover, a practical application for the synthesis of a natural 1-substituted β-carboline, luzongerine A, isolated from Illigera luzonensis was also successfully carried out utilizing this protocol. The effects of synthetic compounds 11 and 11a on nitric oxide (NO) production in LPS/IFN-γ stimulated RAW 264.7 macrophage cells were evaluated in vitro. They displayed significant dose-dependent inhibition of inducible nitric oxide synthase (iNOS).     

A Tamao–Fleming oxidation route to dipeptides bearing N,O-acetal functionality

Tamao–Fleming oxidation of the N-dimethylphenylsilylmethyl group linked to the nitrogen of a peptide bond enables access to dipeptide N,O-acetal functionality. The N-silylmethyl functionality serves as a latent form of the N,O-acetal which is revealed after peptide bond construction.     

A biofriendly sol–gel route to new hybrid gels for enzyme encapsulation

New hybrid gels were prepared from the gelation of glycol-modified tetraethoxysilane (TEOS) in the presence of O-2-hydroxy-3-(trimethylammonio)propyl guar gum (HTPG), and were then used for the in situ encapsulation of papain. Different from the sol–gel process based on commonly used TEOS, the biofriendly sol–gel process developed in this study could be conducted rapidly at ambient temperature without the addition of any organic solvent or acidic catalyst. In particular, the mechanical strength and microstructure of resultant hybrid gel matrix could be modulated by HTPG amount. In comparison with free papain, the encapsulated papain is characteristic of improved enzymatic activity, thermal and storage stability as well as good reusability.     

Pd-catalyzed asymmetric conjugate addition of arylboronic acids to 2-nitroacrylates: a facile route to β-homophenylglycines

Asymmetric conjugate addition of arylboronic acids to 2-nitroacrylamide in the presence of cationic palladium–Chiraphos complex proceeds with high yield and enantioselectivity (73–89% ee) using as low as 0.05–0.25 mol % of the catalyst. The adducts can be smoothly transformed into the corresponding β²-homophenylglycines in two simple steps.     

A synthetic route to 4-alkyl-α-methylhydrocinnamylaldehydes

Research on Chemical Intermediates - The 4-Alkyl-α-methylhydrocinnamylaldehydes (alkyl-isopropyl, isobutyl, methyl) are frequently used fragrances with desired floral (lilac, cyclamen,...     

A new route to α-alkyl-α-fluoromethylenebisphosphonates

A new route to α-alkyl-α-fluoromethylenebisphosphonates, 2 has been developed starting from commercially available tetraethyl fluoromethylenebisphosphonate (1), and alkyl halides using either caesium carbonate in DMF or sodium dimsyl. De-esterification of 2 provided biologically important α-alkyl-α-fluoromethylenebisphosphonic acid, 3, while alkoxide-induced carbon-phosphorus bond cleavage of 2 gave α-fluorophosphonates, 4, which are useful synthons in organic synthesis.     

A novel chemical route to SiO_2 nanowires

A white substance was got by directly heating TiSi powder on Ti foil, under Ar+O2 atmosphere. ED, EDX, SEM and HRTEM studies reveal that the white substance consists of amorphous SiO2nanowires of smooth surface and uniform diameter (40-90 nm). X-ray-induced luminescent emission experiment shows that two broad peaks are at 430 and 570 nm. A one-dimensional growth mechanism, on the basis of the one-dimensional thermal flow during nanowire formation, is discussed.