Swastika Singh

Visible light promoted synthesis of dihydropyrano[2,3-c]chromenes via a multicomponent-tandem strategy under solvent and catalyst free conditions

The development of unique, mild and efficient one pot, multicomponent-tandem synthesis of highly functionalized dihydropyrano[2,3-c]chromenes under photochemical activation is reported. The key feature of the present work is the utilization of visible light which is a ubiquitous, inexpensive and eco-sustainable reagent for catalysing the reaction. The reported methodology is the first example of visible light induced synthesis of dihydropyrano[2,3-c]chromenes and includes several advantages like solvent and catalyst free, environmentally benign reaction conditions, operational simplicity, cost effectiveness, short reaction times, high atom economy, and excellent yields, making it a genuinely green protocol.

Catalyst free, multicomponent-tandem synthesis of spirooxindole-indazolones and spirooxindole-pyrazolines: a glycerol mediated green approach

The development of a versatile new one pot, catalyst free, multicomponent-tandem strategy for assembly of spirooxindole-indazolones and spirooxindole-pyrazolines is described. The reported protocol includes several advantages like environmental friendliness, cost effectiveness, high atom economy, short reaction times and high yields. The reported method is the first green synthesis of spirooxindole-indazolones and spirooxindole-pyrazolines.

A catalyst free, multicomponent-tandem, facile synthesis of pyrido[2,3-d]pyrimidines using glycerol as a recyclable promoting medium

A clean and efficient, multicomponent-tandem strategy for the synthesis of pyrido[2,3-d]pyrimidines is reported in glycerol, a biodegradable and reusable promoting medium. The advantages of the present methodology includes a one-pot catalyst free environmentally friendly approach, 100% atom economy, cost effectiveness, broad substrate scope, operational simplicity, short reaction times, easy workup procedure and high yields.

Synthesis of Copper/Copper-Oxide Nanoparticles: Optical and Structural Characterizations

In the present study, we have synthesized copper/copper‐oxide nanoparticles by laser ablation of copper metal in aqueous solution of sodium dodecyl sulfate. The focused output of 1064 nm wavelength of pulsed Nd:YAG laser is used for ablation. The synthesized nanoparticles are characterized by UV‐visible absorption, X‐ray diffraction, transmission electron microscopy and Raman spectroscopy techniques. The synthesis of copper/copper oxide nanoparticles are confirmed by XRD and Raman studies. The possible mechanism of nanoparticle formation is also discussed.

Bioorganopromoted green Friedländer synthesis: a versatile new malic acid promoted solvent free approach to multisubstituted quinolines

The discovery of a new, malic acid promoted, eco-friendly Friedlander approach to varied multisubstituted quinolines is disclosed. To the best of our knowledge, this is the first report on the use of malic acid, classified as one of the 12 biobased hot molecules by the US Department of Energy, as an organopromoter in organic synthesis and includes many benefits like wide substrate scope, solvent free ambient reaction conditions, short reaction times, operational simplicity, cost effectiveness, high atom economy, good to excellent yields, and recylability of the organopromoter, making it a valuable green alternative to the existing methods. The versatility and practicability of the developed method was further established by its successful application towards the targeted synthesis of some important quinoline molecules and successful scale up.

Catalyst-free glycerol-mediated green synthesis of 5′-thioxospiro[indoline-3,3′-[1,2,4]triazolidin]-2-ones/spiro[indoline-3,3′-[1,2,4]triazolidine]-2,5′-diones

ABSTRACT The development of new catalyst-free green and efficient protocol to access 5′-thioxospiro[indoline-3,3′-[1,2,4]triazolidin]-2-ones/spiro[indoline-3,3′-[1,2,4]triazolidine]-2,5′-diones, potential privileged scaffolds for drug discovery, is disclosed. Key feature of this methodology is the dual use of glycerol—a recyclable, bioorganic compound, as a solvent cum promoter. Other highlights include use of inexpensive reagents, mild reaction conditions, operational simplicity, short reaction time, no need for chromatographic purification, and high yields. GRAPHICAL ABSTRACT

Cadmium Oxide Nanostructures in Water; Synthesis, Characterizations & Optical Properties

Cadmium oxide nanoparticles are synthesized by pulsed laser ablation of cadmium metal in double distilled water, which are found stable for 24 hours. The sample is characterized by using UV‐VIS absorption, scanning electron microscopy, thermo gravimetric analysis, differential thermal analysis, X‐ray diffraction and fourier transform infrared techniques. XRD pattern shows that as synthesized nanopowder has maximum amount of the Cadmium hydroxide rather than its oxide, which converts into Cadmium oxide after annealing at 350° C.

Organocatalytic mediated green approach: A versatile new L-valine promoted synthesis of diverse and densely functionalized 2-amino-3-cyano-4H-pyrans

ABSTRACT The discovery of a new L-valine promoted facile and versatile green synthesis of diversified 2-amino-3-cyano-4H-pyrans using a one pot multicomponent-tandem reaction of aromatic aldehydes, malononitrile, and diverse electron-rich enolizable carbonyl compounds is described. To the best of our knowledge this is the first report on the use of native L-valine as a catalyst in organic synthesis. Environmental friendly, mild reaction conditions, use of easily available inexpensive starting materials, short reaction time, excellent yields, high atom economy, and recyclability of organocatalyst are the major advantages of the disclosed protocol. GRAPHICAL ABSTRACT

A practical green approach to diversified spirochromene/spiropyran scaffolds via a glucose–water synergy driven organocatalytic system

The development of a versatile, new biomimetic glucose–water organocatalytic system promoted, one-pot green and practical method for the synthesis of diversified spirochromenes/spiropyrans is reported. To the best of our knowledge this is the first report on the use of a glucose–water system as a catalyst in organic synthesis. Superior green credentials, operational simplicity, easy scale up and recyclability of the catalyst are the key strengths of this method, which combined with attributes like broad substrate scope, mild reaction conditions, short reaction times, cost effectiveness, high atom economy and good to excellent yields make the present method a distinct improvement over existing methods.

Raman Signal Enhancement Based Chemical Sensing of Volatile Organic Compounds

Surface enhanced Raman scattering based optical sensing (SERS‐OS) is one of the most powerful techniques for the sensitive and selective detection of low concentration analytes. Mostly, metallic nanoparticles, such as Ag, Au and Cu, are used as substrate materials in this technique. Present work is concerned with the possibility of utilization of colloidal zinc nanoparticles, produced by pulsed laser ablation method, as substrate material in SERS‐OS.