Department of Chemistry

We have devised a highly diastereoselective formal [2 + 1] annulation reaction of arylidene/alkylidine-pyrazolones with in situ-generated supported as well as standard pyridinium ylides to construct spirocyclopropanyl-pyrazolones. The cascade approach exhibits a wide range of functional group tolerance, gram-scale capability, and substrate versatility. A diverse range of spirocyclic cyclopropanes was synthesized extensively with both mediators, and the supported pyridine was reused in subsequent cycles. Density functional theory calculations confirmed the formation of spirocyclopropane as the lower energy pathway.

We disclose N′-arylidene-N-acryloyltosylhydrazides as novel skeletons for the synthesis of biologically relevant alkylated pyrazolones through a photoinduced radical cascade with N-(acyloxy)pthalimides as readily available alkyl surrogates. The reaction proceeds through the formation of a photoactivated electron donor-acceptor (EDA) complex between alkyl N-(acyloxy)phthalimide (NHPI) esters and LiI/PPh3 as a commercially available donor system. The reaction exhibits a broad scope and scalability, thereby enabling synthesis of a broad spectrum of functionally orchestrated alkylated pyrazolones under mild and transition-metal-free conditions.

Antibodies and their conjugates of fluorescent labels are widely applied in life sciences research and clinical pathology. Among diverse label types, compact quantum dots (QDs) provide advantages of multispectral multiplexing, bright signals in the deep red and infrared, and low steric hindrance. However, QD-antibody conjugates have random orientation of the antigen-binding domain which may interfere with labeling and are large (20-30 nm) and heterogeneous, which limits penetration into biospecimens. Here, we develop conjugates of compact QDs and Fab′ antibody fragments as primary immunolabels. Fab′ fragments are conjugated site-specifically through sulfhydryl groups distal to antigen-binding domains, and the multivalent conjugates have small and homogeneous sizes (∼12 nm) near those of full-sized antibodies. Their performance as immunolabels for intracellular antigens is evaluated quantitatively by metrics of microtubule labeling density and connectivity in fixed cells and for cytological identification in fixed brain specimens, comparing results with probes based on spectrally-matched dyes. QD-Fab′ conjugates outperformed QD conjugates of full-sized antibodies and could be imaged with bright signals with 1-photon and 2-photon excitation. The results demonstrate a requirement for smaller bioaffinity agents and site-specific orientation for the success of nanomaterial-based labels to enhance penetration in biospecimens and minimize nonspecific staining.

In this communication, we designed a highly selective camphor sulfonyl functionalized crown-ether-tethered calix[4]arene-derived organocatalyst for asymmetric Strecker reaction to provide the desired cyano adducts in high yields (∼99.9% yield) and enantioselectivities (up to 99.3% ee). Furthermore, 2 step facile syntheses of the antiplatelet drug (S)-clopidogrel exemplify the potential of this method for the preparation of commercial compounds.

Indolyl thioethers and indolin-2-one motifs are extremely common in pharmaceuticals and organic materials, therefore developing a method to create these scaffolds is considered to be a vital endeavour in the chemical sciences. Here we have reported a unified strategy developed by the fine-tuning of catalyst-solvent combination [SOCl2 /AlCl3 in CHCl3 and SOCl2/DMSO (1 : 1) in CHCl3 at 25 °C] towards selective functionalization of Indole to synthesize 2,2′-thiobisindoles and 3-chloro-3-alkyl substituted oxindoles selectively in one-pot manner with good to satisfactory yield (52-86 %; 26 Examples). In application, reactions of 3-subsituted indole and isatin derivatives produced the 1-(chloromethyl) indoline-2,3-diones by just changing the reaction condition (60 °C), which shows the synthetic utility of the developed method.

This chapter provides a concise overview of 2D supercapacitors incorporating nanostructured carbon-based materials, MXene, transition metal dichalcogenides (TMDs), black phosphorus (BP), hexagonal boron nitride (h-BN), carbon nitride, and metal oxides/hydroxides, emphasizing their significance in the near future. The introduction discusses supercapacitor classification, key components, and the pivotal role of selecting and designing electrode materials, along with their advantages. Furthermore, the chapter explores various preparation methods for 2D materials, delving into their applications in supercapacitors, and presenting a balanced examination of their advantages and disadvantages. The discussion concludes by addressing practical challenges associated with 2D supercapacitors, offering insightful suggestions to overcome these obstacles, thereby paving the way for their limitless applicability in diverse fields.

Metal oxide-carbon nanocomposites offer an interesting platform for electrochemical sensing due to the synergistic effect of a highly active semiconducting surface and conducting carbon as the supporting backbone. In this work, the in situ synthesis of SnO2 with reduced graphene oxide (rGO) led to the formation of small, uniform SnO2 nanoparticles, measuring 10-20 nm in size, whereas the inclusion of multiwalled carbon nanotubes (MWCNT) resulted in the formation of (200) oriented SnO2 nanoplatelets of ∼200 nm. X-ray photoelectron spectroscopy (XPS) demonstrates a chemical interaction between Sn and C rather than physical adherence. The cyclic voltammograms (CVs) of SnO2-rGO and SnO2-MWCNT display high peak current density and small ΔE in comparison to SnO2, signifying fast electron transfer, reversibility, and enhanced electrochemically active sites. Under optimized experimental conditions of square wave anodic stripping voltammetry (SWASV), the nanocomposites demonstrate high sensitivity (3.9, 9.9, 45.5, and 25.4 mA cm-1 ppb-1) and a low detection limit (in ppb) toward Cd2+, Pb2+, Cu2+, and Hg2+, respectively. The high selectivity of SnO2-rGO for Cd2+ and Pb2+ ions and SnO2-MWCNT for Hg2+ and Cu2+ in a complex metal ion environment is encouraging and is probed by using density functional theory (DFT). Additionally, an artificial neural network (ANN)-based model justifies the sensor’s accuracy and precision for real-time, on-site detection of heavy metal ions directly in tap water.

Detection of molecular anions in interstellar media implies that negatively charged species play a prominent role in astrochemical reactions. Among the observed species, carbon chain anions are important, as they can be precursors for the production of complex organic molecules. These anions can form either via direct electron attachment to the corresponding neutral species or through chain growth reactions of smaller anions, resulting in longer chains. In a recent study, crossed beam experiments coupled with velocity map imaging techniques were used to investigate the carbon chain growth reaction C2n- + C2H2 → C2n+2Hm- + H2-m (n = 1-3, m = 0,1). Products and branching ratios were established from experimental data. In the present work, electronic structure calculations and on-the-fly direct dynamics simulations were used to study these reactions. Energy profiles were investigated by using different density functional methods. Direct trajectory simulations were performed at the experimental collision energies using the B3LYP/6-31+G* level of theory. Trajectory analysis showed a variety of reaction pathways, and detailed atomic-level reaction mechanisms are presented.

A visible light-induced green and sustainable N−H functionalization of (aza)uracils with α-diazo esters leading to imide alkylation is described. The reaction does not require any catalyst or additive and proceeds under mild conditions. Moreover, an intriguing three component coupling was observed when (aza)uracils were allowed to react with α-diazo esters in cyclic ethers (e. g. 1,4-dioxane, THF) as a solvent. Both the insertion and three-component coupling features broad scope with good to excellent yields and appreciable functional group tolerance. Notably, the divergent method enables modification of natural products and pharmaceuticals, thereby facilitates access to potentially biologically active compounds.