Lokesh Kumar Kumawat

2-(Alkylamino)-3-aryl-6,7-dihydrobenzofuran-4(5H)-ones: Improved Synthesis and their Photophysical Properties

Furans are an important class of compounds and exhibit a diverse range of activities and properties. As such, improved synthetic access to furans is an important research goal. In the present report, a solvent- and catalyst-free reaction between 5,5-dimethyl-1,3-cyclohexanedione (dimedone), an aryl aldehyde and an isocyanide under microwave irradiation is presented. This method is significantly improved from previously described protocols in terms of applicability of wide ranging aryl aldehydes, better yields, shorter reaction times, facile work up and essentially no need of column chromatography. The photophysical properties of this series of compounds were studied for their possible applicability in the field of metal ion sensors. In solution, two compounds, 2-(cyclohexylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 i) and 2-(tert-butylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 j), underwent an observable color change from yellow to colorless in the presence of aluminum(III) ions. Further studies to investigate the UV absorption and luminescence behavior of these compounds revealed their utility as “naked-eye sensors” for aluminum detection.

Rational design of the first furoquinolinol based molecular systems for easy detection of Cu2+ with potential applications in the area of membrane sensing

Two molecular probes based on the furoquinolinol (FQ) framework have been rationally designed for the rapid detection and trace level quantification of Cu2+ in organic and semi-aqueous mediums. Synthesized FQs were extensively examined for their Cu2+ sensing abilities by UV-vis/fluorescence experiments, NMR titrations and DFT based calculations. Higher binding constant [2.11 × 104 M−1 (FQ1) and 1.87 × 104 M−1 (FQ2)], low detection limit [1.52 × 10−7 M (FQ1) and 2.13 × 10−7 M (FQ2)], high selectivity, fast response, wide operational pH range, and repeated usability are some of the salient features of the reported sensors. Furthermore, these compounds (FQs) retained their metal detection abilities in thin PVC membranes.

Structure property studies revealed a new indoylfuranone based bifunctional chemosensor for Cu2+ and Al3+

The present report highlights the role of comprehensive structure property relationships (SPRs) in the discovery of a new and more effective molecular system for sensing purposes. From an extensive survey of different classes of amino substituted annulated furanones, it was realized that with some exceptions, these functionalized furanones could sense Cu2+ ions in the semi-aqueous phase irrespective of the nature of substituents; furthermore the same scaffolds could also detect Al3+, if the aldehydic position is specifically filled by a 3-indoyl group. As a result, amino substituted annulated furanones with 3-indoyl groups could detect both metal ions, response time of which mainly depends on the overall molecular framework. After replacing different furanone frameworks, a dual metal ion sensor (for Cu2+ and Al3+) with short response time and high selectivity and association constant was identified. The proposed bifunctional sensor displayed a distinct but observable response (turn off colorimetric for Cu2+ and turn on fluorescence for Al3+) to both metal ions with potential applications in the area of real sample analysis and membrane sensing.

Optical and electrochemical dual channel sensing of Cu 2+ using functionalized furo[2,3- d ]pyrimidines-2,4[1 H ,3 H ]-diones

Owing to their easy accessibility and high degree of structural and functional diversity, many multicomponent reactions (MCRs) have been a rich source of conjugate π-systems, functionalised chromophores (or fluorophore) and redox active molecules. Despite their high explorative potential and practical benefits, only a few MCR products have been so far investigated for their metal sensing abilities. In the present report, two furopyrimidinones (FPys) based molecular systems have been synthesized by [4+1] cycloaddition based MCR sequence. Designed chemosensors displayed optic (absorption spectra) as well as electroanalytical (ion selective electrode) response toward Cu2+ ion in solution and membrane phase respectively (dual channel sensing). Different aspects of both the sensing phenomena such as selectivity, association constants, detection limit, membrane composition etc. were studied in detail using UV-Vis spectroscopy, NMR titration and cell assembly. Both the compounds showed excellent performance characteristics such as high selectivity, acceptable affinity and low detection limits (10-7M) in both sensing assays with potential utility in the area of sample monitoring.