7 research outputs found
Enantioselective syntheses of diquinane and (cis, anti, cis)-linear triquinanes
The enantioselective syntheses of diquinane and cis, anti, cis-linear triquinanes, starting from the readily available (S)-campholenaldehyde, employing an intramolecular rhodium carbenoid CH insertion reaction, are described. (C) 2010 Elsevier Ltd. All rights reserved
First Cu-Nanostar as Sustainable Catalyst Realized through Synergistic Effects of Bowl-shaped Features and Surface Activation of Sporopollenin Exine
Recently, nanostar-shaped structures, including gold nanostars (NS), have drawn much attention for their potential use in surface-enhanced Raman spectroscopy (SERS) and catalysis. Yet, very few studies have been conducted on Cu-Au hybrid NS, and there are none for Cu-based NS. Herein, we describe an effective method for controlling copper oxide nanostar (ESP-PEI-CuI/IIO-NS) growth using sporopollenin as a sustainable template material. However, ESP-PEI-CuI/IIO-NS growth depends on sporopollenin surface functionalization. Sporopollenin surface activation was done by amine functionalization with polyethyleneimine (PEI), without which ESP-PEI-CuI/IIO-NS growth was not observed. The sporopollenin’s exine (outer wall) has bowl-like structures, which mediates the growth of Cu nanorods, resulting in an NS morphology. Furthermore, due to their increased surface area, ESP-PEI-CuI/IIO-NS showed excellent catalytic activity for Huisgen 1,3-dipolar cycloadditions even when used in H2O and without additives under greener conditions. This approach utilising biomass as a sustainable template would pave the way for developing controlled growth of nanostructures for SERS-related and catalytic applications
New Access to the Synthesis of 1,1,4,4-Tetracyanobuta-1,3-Diene-Based Push–pull Chromophores Using Tetracyanoethylene Oxide via [3+2] Cycloaddition-Ring Opening Reactions
Herein we report a new way to access the synthesis of established invaluable push–pull chromophores based on 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) using tetracyanoethylene oxide (TCNEO) upon reaction with alkynes substituted with an electron-donating group (EDG) via [3+2] cycloaddition (CA) followed by ring-opening (RO) reactions. Further, we uncovered that the facile [3+2] CA–RO reaction under simpler reaction condition is possible due to the presence of EDG group, otherwise, even the formation of [3+2] cycloadduct without EDG requires harsher condition and does not lead to TCBD as reported earlier in 1965 by Linn and Benson
Unravelling the effect of non-drug spacers on a true drug-polymer and a comparative study of their antimicrobial activity
Several studies have been conducted on polymerisation of drug units using spacers or other polymeric units. In order to study the importance of spacers in drug polymers, we designed polymers with and without spacers. As a proof of concept, herein, we present a comparative study on the efficacy of antibacterial activity using a polymeric biocide (PB) C0P1 having no spacer (0%) and two other PBs with varied spacer content (C2P2:29%, C10P3:53%). We considered C0P1 as a potential new type of PB generated from a widely used fluoroquinolone antibiotic, ciprofloxacin 1, by a simple self-condensation activation with thionyl chloride. Monomer 2 (formylated methyl ester of 1) was polymerised with ethylenediamine (C2) and 1,10-diaminodecane (C10) to provide C2P2 and C10P3, respectively. The trend for minimum inhibitory concentration study against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was observed as 1>C0P1>C2P2=C10P3>>2. Further, after coating on nylon threads, the non-spacer polymer C0P1 showed enhanced zone of inhibition (ZOI) than monomer 1 as well as the spacer polymers owing to its superior coating ability and sustained drug release capabilities. Thus, this study clearly states that the bio-efficacy of a drug-polymer could be retained and enhanced in the absence of non-bioactive spacer units
A Subtle Change in Substituent Enabled Multi-Ways Fluoride Signals Including Paper-Strip Colorimetric Detection Using Urea Receptor Functionalized 1,1,4,4-Tetracyanobuta-1,3-Diene-Based Push-Pull Chromophore
A simple color change detection by the naked-eye using untreated paper for a biologically relevant fluoride (F–) anion in water is a challenge. New non-planar push-pull chromophore involving intramolecular charge-transfer (ICT) from urea donor in 2,3-disubstituted-1,1,4,4-tetracyanobuta-1,3-diene (TCBD) turns out to be an efficient system for detecting F– ion giving various output signals. But, replacing phenyl (Ph) at C3-position with 4-(dimethylamino)phenyl (DMA) led to the absence of colorimetric and fluorometric detections due to the masking and quenching, nature of strong ICT by the DMA. NMR and electrochemical studies revealed that the sensing mechanism is governed by H-bonding as well as the deprotonation of N–H attached with TCBD moiety which reduces the HOMO–LUMO gap and causes the dramatic color change. Coupled with excellent sensitivity (3 ppm) and specificity towards F–, a successful demonstration of cheap tissue paper-based visual strip-detection in aqueous is presented
A Study of [2+2] Cycloaddition–Retroelectrocyclization in Water: Observation of Substrate-driven Transient Nanoreactor Induced New Reactivity
Organic solvents limit [2+2] cycloaddition-retroelectrocyclization (CA–RE) in biological fields. We examined the formation of 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) through CA–RE reactions and their unusual reactivity to produce N-heterocyclic compounds when surfactant nature and concentrations were varied in the aqueous phase. An environment in which transient self-assembly (vesicles) was induced by substrate and surfactant molecules initiated new reactivity through H2O addition on the TCBD generating enol form of the intermediate which results in the formation of the 6,6-dicyano-heteropentafulvene (amidofulvene) compound while lamellar sheets at higher concentrations favored TCBD generation. Interestingly, the amidofulvene underwent a clean transformation to 6-membered-heterocycles via keto-enol tautomerism mediated by a polar aprotic solvent which resembles cardiotonic drugs (milrinone, amrinone), opening up a new avenue for drug discovery. Unlike organic solvent-mediated CA–RE reactions, the present nanoreactor-mediated approach enabled the selective production of TCBDs as well as new heterocycles using H2O as a green solvent. Besides the widely explored organic electronics/materials, we believe that this study would help overcome the long-standing limitation of CA–RE reaction applicability in biological fields
Design and Synthesis of Aviram-Ratner-Type Dyads and Rectification Studies in Langmuir-Blodgett (LB) Films
The design and synthesis of Aviram-Ratner-type molecular rectifiers, featuring an anilino-substituted extended tetracyanoquinodimethane (exTCNQ) acceptor, covalently linked by the sigma-spacer bicyclo[2.2.2]octane (BCO) to a tetrathiafulvalene (TTF) donor moiety, are described. The rigid BCO spacer keeps the TTF donor and exTCNQ acceptor moieties apart, as demonstrated by X-ray analysis. The photophysical properties of the TTF-BCO-exTCNQ dyads were investigated by UV/Vis and EPR spectroscopy, electrochemical studies, and theoretical calculations. Langmuir-Blodgett films were prepared and used in the fabrication and electrical studies of junction devices. One dyad showed the asymmetric current-voltage (I-V) curve characteristic for rectification, unlike control compounds containing the TTF unit but not the exTCNQ moiety or comprising the exTCNQ acceptor moiety but lacking the donor TTF part, which both gave symmetric I-V curves. The direction of the observed rectification indicated that the preferred electron current flows from the exTCNQ acceptor to the TTF donor