Browsing by Author "Amit Kumar Gupta"

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An eco-safe approach to benzopyranopyrimidines and 4H-chromenes in ionic liquid at room temperature
(2012) Amit Kumar Gupta; Kumkum Kumari; Neetu Singh; Dushyant Singh Raghuvanshi; Krishna Nand Singh
An environmentally benign, ionic liquid promoted multicomponent protocol to benzopyrano(2,3-d)pyrimidines and 4H-chromenes has been developed at room temperature. Results of the reaction depend on the nature of the nucleophile used in the reaction. Secondary amines result in the formation of benzopyrano(2,3-d)pyrimidines, whereas thiols give rise to 4H-chromenes under the same set of reaction conditions. © 2011 Elsevier Ltd. All rights reserved.
Effects of heavy metal and metalloid contamination on the soil microbial response: An overview
(Nova Science Publishers, Inc., 2011) Amit Kumar Gupta; Rajeev Pratap Singh; Anita Singh; Mahamad Hakimi Ibrahim
Heavy metals constitute a heterogeneous group of elements varying in their chemical properties and biological functions. Pollution of heavy metals in soil is of great concern for human health and functioning of ecosystem as they have toxic effects on plants, animals and human being. Contamination of soil by heavy metal results from both anthropogenic as well as natural activities. Anthropogenic activities includes mining, smelting operation, sewage sludge or wastewater, small scale industries etc. These activities may increase the levels of heavy metals in soil upto the toxic level. Heavy metals are persistent in nature, therefore get bioaccumulated in soils and they can also affect soil microbial activity. Microbial communities in soil are made up of five major groups, namely: bacteria, fungi, algae, archaea and protozoa. Among all, bacteria are the most abundant group and usually more numerous than the others. Soil microbes play vital roles in various aspects of the terrestrial ecosystem, such as soil fertility during plant growth, including agronomic activities. Soil microbial biomass represents the fraction of the soil responsible for the energy and nutrient cycling and regulation of organic matter transformation. It is through the microbial biomass, mineralization of important organic elements take place. Microbial activity is very closely related with soil fertility. Microbial biomass may be a sensitive indicator of metal stress.Its suitability in environmental monitoring as an indicator of soil pollution is limited because of its high spatial variability. The present chapter deals with various aspects of effects of heavy metal pollution and its effect on soil microbial response. © 2011 by Nova Science Publishers, Inc. All rights reserved.
Microwave assisted organic synthesis: Cross coupling and multicomponent reactions
(Bentham Science Publishers, 2013) Amit Kumar Gupta; Neetu Singh; Krishna Nand Singh
Impact of microwave radiation on organic chemistry has been assessed by workers time to time. This review covers selected recent examples form cross-coupling reactions, multicomponent reactions along with some cycloaddition reactions to reveal the impact of microwave on organic synthesis. © 2013 Bentham Science Publishers.
Nickel-mediated N-arylation with arylboronic acids: An avenue to Chan-Lam coupling
(2012) Dushyant Singh Raghuvanshi; Amit Kumar Gupta; Krishna Nand Singh
An efficient use of NiCl 2·6H 2O, for the cross-coupling of arylboronic acids with various N-nucleophiles, has been demonstrated. The method is practical and offers an alternative to the corresponding Cu-mediated Chan-Lam process for the construction of the C-N bond. © 2012 American Chemical Society.
NiCl 2·6H 2O as recyclable heterogeneous catalyst for N-arylation of amines and NH-heterocycles under microwave exposure
(2012) Amit Kumar Gupta; G. Tirumaleswara Rao; Krishna Nand Singh
NiCl 2·6H 2O has been proven to be an effective catalyst for the coupling of amines with aryl iodides without ligand under solvent-free conditions employing microwave irradiation. Reactions cleanly result in coupled products in a short reaction time. The catalyst, being heterogeneous, is recovered by filtration and is recyclable. © 2012 Elsevier Ltd. All rights reserved.