• LAKSHMI KANTAM MANNEPALLI

      Articles written in Journal of Chemical Sciences

    • Synthesis of substituted guanidines using Zn-Al hydrotalcite catalyst

      Lakshmi Kantam Mannepalli Venkanna Dupati Swarna Jaya Vallabha Manorama Sunkara V

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      Substituted guanidines were synthesized by the guanylation of amines with carbodiimides using Zn-Al hydrotalcite (Zn-Al HT) catalyst. Zn-Al HT was prepared by co-precipitation method and characterized by X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman and Thermogravimetric-Differential Thermal Analysis (TG-DTA). The heterogeneous catalyst afforded moderate to good yields ($\tilde r$ 50-60 %) of substituted guanidines in toluene at 110°C in 12 h. The catalyst was recovered quantitatively by simple filtration and reused for three cycles with consistent activity. The XRD and FTIR studies of the used catalyst shows no variation in the structure of the catalyst even after three recycles.

    • Synthesis of quinoxaline derivatives from terminal alkynes and o-phenylenediamines by using copper alumina catalyst

      AKHIL V NAKHATE KALIDAS B RASAL GUNJAN P DESHMUKH SHYAM SUNDER R GUPTA LAKSHMI KANTAM MANNEPALLI

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      An efficient method for the synthesis of quinoxaline derivatives through oxidative coupling of o-phenylenediamines (OPD) with terminal alkynes by using copper-alumina (Cu-Al) catalyst was described. A series of Cu-Al catalysts with different mole ratios of Cu ²⁺ /Al ³⁺, 2:1 (Cu-Al-1), 2.5:1 (Cu-Al-2) and 3:1 (Cu-Al-3) were prepared by co-precipitation method followed by calcination and their activity was checked for the synthesis of quinoxaline derivatives. Cu-Al-2 showed excellent activity at 60 ◦C in presence ofK ₂CO ₃. The catalyst is inexpensive, recyclable and environmentally benign. The fresh and recycled catalysts were characterized by different analytical techniques. Different reaction parameters were optimized; catalyst screening, solvent, base and temperature. The protocol was extended towards different substrates.

    • W/HAP catalysed N-oxidation of tertiary amines with H2O2 as an oxidant

      RAKHI VISHWAKARMA VIRENDRA RATHOD LAKSHMI KANTAM MANNEPALLI

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      Synthesis of several N-oxides with tungsten exchanged hydroxyapatite (W/HAP) in the presenceof 30% hydrogen peroxide (H2O2) as an oxidant is presented. A process with aqueous H2O2, a cheap andclean oxidant with an active catalyst is developed to reduce waste production and meet the requirements ofgreen chemistry. Several tertiary amines have been efficiently oxidized to their corresponding N-oxides withexcellent yields. The as-synthesized catalyst (W/HAP) is characterized using BET, FTIR, SEM, ICP-OES andXRD. Effect of catalyst loading , temperature and oxidants were studied. A kinetic model has been developedto determine the reaction rate at different temperatures and activation energy for the model reaction.

      Synopsis. Synthesis of several N-oxides using tungsten exchanged hydroxyapatite (W/HAP) in the presence of 30% hydrogen peroxide (H2O2) as an oxidant is presented. A process with aqueous H2O2, a cheap and clean oxidant with an active catalyst is developed to reduce waste production and meet the requirements of green chemistry.

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