Boric Acid–Catalyzed One-Pot Access to 7-Aryl-benzopyrano[4,3-b] benzopyran-6,8-diones Under Aqueous Micellar Conditions

A mild protocol for the synthesis of 7-arylbenzopyrano[4,3-b]benzopyran-6,8-diones by three-component reaction of 4-hydroxycoumarin, aromatic aldehyde, and 5,5-dimethylcyclohexane-1,3-dione (dimedone) with boric acid catalyst under aqueous micellar conditions is described. Good to excellent yield, high selectivity, tolerance of several common functional and protecting groups, and green features including avoidance of organic solvent in the reaction as well as isolation stage and use of nontoxic water-compatible mild Lewis acid catalyst are key attractive features of the protocol.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Room temperature ultralow threshold GaN nanowire polariton laser

We report ultralow threshold polariton lasing from a single GaN nanowire strongly coupled to a large-area dielectric microcavity. The threshold carrier density is 3 orders of magnitude lower than that of photon lasing observed in the same device, and 2 orders of magnitude lower than any existing room-temperature polariton devices. Spectral, polarization, and coherence properties of the emission were measured to confirm polariton lasing.     

Quantum criticality between topological and band insulators in 3+1 dimensions

Four-component massive and massless Dirac fermions in the presence of long range Coulomb interaction and chemical potential disorder exhibit striking fermionic quantum criticality. For an odd number of flavors of Dirac fermions, the sign of the Dirac mass distinguishes the topological and the trivial band insulator phases, and the gapless semimetallic phase corresponds to the quantum critical point that separates the two. Up to a critical strength of disorder, the semimetallic phase remains stable, and the universality class of the direct phase transition between two insulating phases is unchanged. Beyond the critical strength of disorder the semimetallic phase undergoes a phase transition into a disorder controlled diffusive metallic phase, and there is no longer a direct phase transition between the two types of insulating phases.     

Interfacial insights on the dibenzo-based crown ether assisted cesium extraction in [BMIM][Tf2N]–water binary system

The distribution coefficient of Cs is estimated using dibenzo-21-crown-7 (DB21C7) and di-benzo-18-crown-6 (DB18C6) in 1-butyl-3-methylimidazolium bis (trifluroromethanesulphonyl) imide (BMIMTF2N) ionic liquid by performing solvent extraction experiments. In addition, molecular dynamics studies on the extraction of cesium (Cs⁺) ion transfer from the aqueous phase to the BMIMTF2N phase is reported. The experimental findings gave a cesium distribution coefficient of 0.218 and 0.326, which agrees closely with the values of 0.2 and 0.5 obtained from MD simulation for the ionophores DB18C6 and DB21C7, respectively. Thus MD simulation may be helpful in screening the solvents prior to the experiments.

     

Low-power bacteriorhodopsin-silicon n-channel metal-oxide field-effect transistor photoreceiver

A bacteriorhodopsin (bR)-silicon n-channel metal-oxide field-effect transistor (NMOSFET) monolithically integrated photoreceiver is demonstrated. The bR film is selectively formed on an external gate electrode of the transistor by electrophoretic deposition. A modified biasing circuit is incorporated, which helps to match the resistance of the bR film to the input impedance of the NMOSFET and to shift the operating point of the transistor to coincide with the maximum gain. The photoreceiver exhibits a responsivity of 4.7 mA/W.     

Elucidation of post-PKS tailoring steps involved in landomycin biosynthesis

The functional roles of all proposed enzymes involved in the post-PKS redox reactions of the biosynthesis of various landomycin aglycones were thoroughly studied, both in vivo and in vitro. The results revealed that LanM2 acts as a dehydratase and is responsible for concomitant release of the last PKS-tethered intermediate to yield prejadomycin (10). Prejadomycin (10) was confirmed to be a general pathway intermediate of the biosynthesis. Oxygenase LanE and the reductase LanV are sufficient to convert 10 into 11-deoxylandomycinone (5) in the presence of NADH. LanZ4 is a reductase providing reduced flavin (FMNH) co-factor to the partner enzyme LanZ5, which controls all remaining steps. LanZ5, a bifunctional oxygenase-dehydratase, is a key enzyme directing landomycin biosynthesis. It catalyzes hydroxylation at the 11-position preferentially only after the first glycosylation step, and requires the presence of LanZ4. In the absence of such a glycosylation, LanZ5 catalyzes C5,6-dehydration, leading to the production of anhydrolandomycinone (8) or tetrangulol (9). The overall results provided a revised pathway for the biosynthesis of the four aglycones that are found in various congeners of the landomycin group.     

An efficient one-pot organocatalytic synthesis of 9-(1H-indol-3-yl)-xanthen-4-(9H)-ones under mild aqueous micellar conditions

An efficient and facile l-proline-catalyzed three-component coupling of 2-hydroxybenzaldehyde, 5,5-dimethyl-1,3-cyclohexanedione (dimedone), and indole has been accomplished under mild aqueous micellar conditions to deliver a small library of 9-(1H-indol-3-yl)-xanthen-4-(9H)-ones of potential biological relevance. Under optimized conditions [10 mol % of l-proline, water (2 mL), SDS (23 mg, 0.08 mmol), rt], the reaction was highly selective toward the target compound and essentially free from competitive two-component byproduct formation.     

Antitumour activity of Terminalia arjuna leaf against Ehrlich ascites carcinoma in mice

Terminalia arjuna Roxb. (Combretaceae), commonly known as 'Arjuna', is a large tree occurring throughout the Indian peninsula. This study was undertaken to evaluate the methanol extract of T. arjuna leaf (META) for antitumour activity against Ehrlich ascites carcinoma (EAC) in Swiss albino mice. Twenty-four hours after intraperitonial inoculation of tumour (EAC) cells in mice, META was administered at 100 and 200?mg?kg(-1) body weights for 9 consecutive days. On day 10, half of the mice were sacrificed and the rest kept alive for an assessment of the increase in life span. The antitumour effect of META was assessed by evaluating tumour volume, tumour weight, viable and non-viable tumour cell counts, median survival time and increase in life span of EAC-bearing hosts. Haematological profiles were estimated. META showed a significant (p<0.001) decrease in tumour volume, tumour weight and viable cell count, and also increased the life span of EAC-bearing mice. Haematological profiles were significantly (p<0.001) restored to normal levels in META-treated mice compared to the EAC control. Therefore, from this study, it can be concluded that T. arjuna leaf exhibited remarkable antitumour activity against EAC in Swiss mice.     

Fe‐enriched Clay‐coated and Reduced Graphene Oxide‐modified N‐doped Polymer Nanocomposite: A Natural Recognition Element‐based Sensing Electrode for DNT

Dinitrotoluene (DNT) is a signature material of all nitro‐aromatic explosives including the lethal 2,4,6‐trinitrotoluene (TNT). A clay‐modified reduced graphene oxide (rGO)‐polymer nanocomposite was prepared as sensing electrode for the detection of (DNT) in the aquatic systems. rGO was in situ dispersed in the electro‐conductive N‐doped phenol/formaldehyde polymer and the clay ‘montmorillonite’ was coated on the nanocomposite. The clay, containing iron as one of its mineral components, served as the recognition element for DNT. Tested using electrochemical measurement techniques – cyclic voltammetry and differential pulse voltammetry, the prepared sensing electrode exhibited a low detection limit (0.0016 μM) on signal to noise ratio basis (S/N=3) and excellent linearity (R²=0.997) over 0.02–10 mg L^?1 with high sensitivity value (428 μA mM^?1 cm^?2) for DNT. The electrode showed negligible interference with the gravimetric and volumetric salts commonly present in seawater, and also, with explosive derivatives. The separate tests performed in a simulated seawater confirmed the suitability of the prepared electrode for use in field applications.     

Cu(I)/Fe(III) promoted dicarbonylation of aminopyrazole via oxidative CH coupling with methyl ketones

Cu(I)/Fe(III) promoted C4-dicarbonylation of 5-aminopyrazole is developed. The strategy involved radical triggered direct oxidative coupling of 5-aminopyrazoles with methyl ketones using aerial oxygen as a source of oxygen in newly generated carbonyl group. CuI is used as catalyst and FeCl₃·6H₂O is used as additive and the reaction proceeded at 120?°C in DMSO for 9–12?h. It is found that use of Cu(II) catalyst gives the thiomethylated product by reacting with DMSO instead of oxidative coupling. A plausible mechanism is also given.