Allenes with two carbon–carbon double bonds belong to a unique class of unsaturated hydrocarbons. The central carbon atom of allene is sp hybridized and forms two σ-bonds and two π-bonds with two terminal sp² hybridized carbon atoms. The chemistry of allenes has been well documented over the last decades. They are more reactive than alkenes due to higher strain and exhibit significant axial chirality, thus playing a vital role in asymmetric synthesis. Over a variety of organic transformations, allenes specifically undergo classical metal catalyzed cycloaddition reactions to obtain chemo-, regio- and stereoselective cycloadducts. This review briefly describes different types of annulations including [2+2], [2+2+1], [3+2], [2+2+2], [4+2], [5+2], [6+2] cycloadditions using titanium, cobalt, rhodium, nickel, palladium, platinum, gold and phosphine catalyzed reactions along with a mechanistic study of some highlighted protocols. The synthetic applications of these reactions towards the synthesis of natural products such as aristeromycin, ent-[3]-ladderanol, waihoensene(−)-vindoline and (+)-4-epi-vindoline have also been described.

The emerging concepts of sustainable textiles and controlled production strategy demands ideally zero emissions of contaminants into the aquatic environment. However, the currently in-practiced conventional processes in textiles dispose of a number of contaminants especially super toxic synthetic dyes as effluents. In recent years, nanomaterials have become attractive choice for eco-friendly removal of organic dyestuff. Accordingly, this article reports synthesis and characterization of biocomposite wherein copolymer of polyaniline (PANI) and Polypyrrole (PPY) was grafted onto hydroxyethyl cellulose (HEC). Further, adsorption properties of as-prepared composite were evaluated using textile dyes Rhodamine B (RhB) and methyl Orange (MO)- as model adsorbate. The characterization of novel biocomposite (HEC/PANI-PPy) was carried out using Fourier Transform Infrared (FT-IR), Brunauer-Emmett-Teller analyzer (BET), Scanning Electron Microscope (SEM), and powder X-ray diffraction (XRD). The operational parameters such as dye initial concentration, adsorbent amount, pH and contact time were also studied to evaluate the efficiency level of the prepared biocomposite. Interestingly, the composite-mediated adsorption of RhB and MO followed pseudo-second order and the Langmuir isotherm. It is found that the adsorption capacity HEC/PANI-PPy is 30.06 and 29.3 for RhB and MO respectively. Thus, HEC/PANI-PPy is an inexpensive and highly efficient adsorbent that could be employed for could be employed for the separation and removal of toxic organic dyes from polluted textile effluents.

Growing industry and its effluents create a serious environmental concern. Various industrial wastes such as toxic dyes and volatile organic compounds are posing a threat to a clean environment because of their non-biodegradable nature and high chemical stability. In recent years, the degradation of toxic dyes and drugs by photo-catalysts has gained much importance and proved a successful approach to capture light by hybrid photo-catalysts for decomposing toxic organic molecules. This work presents the synthesis of a poly(o-anisidine)-based composite with graphitic carbon nitride and zinc oxide (POA/g-C₃N₄/ZnO) and its utilization as a photo-catalyst. Various analytical techniques investigated the synthesized photo-catalysts’ chemical structure, crystallinity, and morphology. The degradation of Congo red dye evaluated the efficiency of the photo-catalyst in an aqueous medium under ultraviolet light. It was revealed that the photo-catalytic activity of the synthesized POA/g-C₃N₄/ZnO composites show 81.43%, 92.28%, and 87.05% degradation. This sustainable composite will be highly beneficial to treat industrial wastewater to make our environment clean.

Electrically conductive polyorthochloroaniline/chromium nanocomposites (POC/Cr NCs) were prepared by in situ chemical oxidative polymerization of orthochloroaniline in the presence of Cr nanoparticles (Cr NPs). The load percentage of Cr nanofiller was varied in POC matrix to investigate the effect of Cr nanoparticles on the properties of the nanocomposites. The composition, structure, and morphology of POC and its composites were examined by Scanning electron microscopy, Fourier transform infrared spectroscopy, and UV–visible spectroscopic analysis. The antibacterial potential of POC and its composites was evaluated by the disc diffusion method against Escherichia coli and Bacillus subtilis. The results showed the improved antibacterial potential with the increase in the load percentage of nanofiller. The electrical conductivity of polymer and its composites was measured and correlated with the load percentage. The results showed that electrical conductivity of the composites was enhanced with the increase in load percentage of Cr nanoparticles.

Piperazine is a privileged moiety that is a structural part of many clinical drugs. Piperazine-based scaffolds have attracted the attention of pharmaceutical and medicinal scientists to develop novel, efficient therapeutic agents owing to their significant and promising biological profile. In the current study, an ecofriendly ultrasonic-assisted synthetic approach was applied to achieve a novel series of 1-tosyl piperazine dithiocarbamate acetamide hybrids 4a–4j, which was evaluated for in vitro tyrosinase inhibition and thrombolytic and hemolytic cytotoxic activities. Among all the piperazine-based dithiocarbamate acetamide target molecules 4a–4j, the structural analogs 4d displayed excellent tyrosinase inhibition efficacy (IC₅₀ = 6.88 ± 0.11 µM) which was better than the reference standard drugs kojic acid (30.34 ± 0.75 µM) and ascorbic acid (11.5 ± 1.00 µM), respectively, which was further confirmed by in silico induced-fit docking (IFD) simulation Good tyrosinase activities were exhibited by 4g (IC₅₀ = 7.24 ± 0.15 µM), 4b (IC₅₀ = 8.01 ± 0.11 µM) and 4c (IC₅₀ = 8.1 ± 0.30 µM) dithiocarbamate acetamides, which were also better tyrosinase inhibitors than the reference drugs but were less active than the 4d structural hybrid. All the derivatives are less toxic, having values in the 0.29 ± 0.01% to 15.6 ± 0.5% range. The scaffold 4b demonstrated better hemolytic potential (0.29 ± 0.01%), while a remarkably high thrombolytic chemotherapeutic potential was displayed by analog 4e (67.3 ± 0.2%).