This review describes the synthesis of oxygen heterocycles by palladium-mediated cyclization published during 2003 to 2007.

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This paper briefly describes the current status of ecology, fisheries and biodiversity of the River Ganges. Apart from being the original abode of the most prized Indian major carps, viz., Catla catla, Labeo rohita, Cirrhinus mrigala and Labeo calbasu, the river sustains fisheries of large catfish, mahseers, hilsa and other miscellaneous fishes. Over the years the fish catch per kilometre stretch in the river has declined significantly and species composition has changed more in favor of non major carp and miscellaneous species. It has also been observed that some exotic fishes have gained a foothold in the ecosystem at favorable stretches, where flows have drastically reduced as a result of abstraction of water from the main river. Changing hydrology, apart from deteriorating environmental conditions, has been to a large extent responsible for change in the fishery scenario in the river. This change has also affected the income levels of riparian fishers. Review of the data generated, over the years, also indicated deteriorating water quality at the stressed sites. The contamination of river water, sediments and fish with heavy metal and pesticide residues is also a factor of concern. With continued stress on the river system an environmental restoration plan was launched by the Indian authorities; its impacts over the years on ecosystem health is also discussed.

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NiCl2·6H2O and Ni(OAc)2·4H2O were found as efficient catalysts for C-H activation of benzyl and aliphatic amines for an unprecedented multi C-N bond forming cyclization with 1,2-diketones under refluxing toluene to furnish highly substituted and polycyclic imidazoles.

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Palladium-mediated cyclization reactions have been recognized as some of the simplest and useful tools for regio-as well as stereoselective syntheses of carbo-and heterocyclic compounds. In the multi-step syntheses of natural products it is frequently used as one of the most important steps. In this review article, we have summarized the various ways of constructing five-and six-membered heterocyclic rings by palladium-catalyzed intramolecular cyclizations published between 2008 and 2010.