Current Organic Chemistry - Volume 22, Issue 15, 2018

Heterogeneous photocatalysis is widely used in a broad variety of chemical reactions such as oxidations, dehydrogenation and hydrogen transfer. The photocatalyzed reduction of nitro groups has been used to prepare organic compounds with important industrial and biological applications. The formation of the desired compound could be controlled by selecting the adequate reaction conditions such as catalyst and solvent. This review presents a broad overview of the reaction mechanisms in photocatalytic reduction of nitrobenzene to develop a viable route to produce a sole or major product through high chemo- and regio-selectivity under mild conditions. The aniline, azo and azoxy formation is discussed according to catalyst selection, and also solvent effect has been examined. Finally, examples of synthesis of organic compounds via photocatalytic reduction of nitro compounds even in the presence of reducible groups such as carbonyl, cyano, alkyne and alkene are presented.

This review illustrates that oximes and their derivatives are valuable materials for the preparation of different classes of heterocyclic compounds. The main group of reactions included transition metal catalysed or transition metal-free cyclisation of unsaturated oximes. Using these starting materials pyrroles, isoxazoles, pyridines and isoquinolines were prepared. Some heterocyclic systems (for example, seven-membered rings) were obtained by the classical Beckmann rearrangement using novel reagents and conditions. Literature data published between January of 2014 and June of 2017 are included in this review.

Carbon nanotubes (CNTs) because of one-dimensional structure and high surface area as well as their exceptional properties such as excellent mechanical, thermal, electrical and optical properties, are considered as one of the most popular carbon-based nanomaterials in the field of research. These nanoscale tubes have a wide range of applications, including their use in materials science, energy management, electronics, chemical processing, and many other fields. In the present work, the most commonly used methods for amino-functionalization of CNTs have been reviewed. These CNT functionalization methods are generally divided into two groups, covalent and non-covalent modifications which ultimately leads to the formation of the amino (-NH2) functional groups on the CNT surfaces. The amino functional groups because of their excellent chemical properties, such as high electron donating effect and good nucleophilicity, can act as a convenient linker between the CNTs and nanoparticles, ions or the matrix epoxy etc. and thus enables numerous potential applications for amino-functionalized CNTs (NH2-CNTs). Therefore, the applications of NH2-CNT in several fields such as, absorbent for metal ions, the support for preparation of the electrocatalysts, fabrication of (bio) sensors, preparation of NH2-CNT/epoxy nanocomposites, and as vectors for gene therapy, have also been reviewed.

Alkenylaluminum reagents are good nucleophiles for organic reactions because of their high reactivities, the high Lewis acidity of the aluminum center, and their low toxicities. Therefore, alkenylaluminum reagents are widely applied in many of organic reactions. This review summarizes the recent advance of the alkenylaluminum reagents applied in cross-coupling reactions, involving various reaction systems, properties of reaction and synthetic application.

The synthetic and mechanistic aspects of highly energetic pyridine carbenes (PyCs) are discussed for understanding the regio- and stereoselective functionalization of pyridine at rare sites by applying different C-H bond activation methods. Various transition metals and metalloids are used for the generation of corresponding PyCs followed by the formation of substituted pyridines. The functionalization of most focused 2,3,4- positions of pyridine is described with several applications in the synthesis of drugs and natural products, in single-walled carbon nanotubes (SWNTs) and in dye-sensitized solar cells (DSSCs) as the energy storage compounds.

Environmental pollution and contamination is a result of direct or indirect effects of human activities and industrialization. Nowadays, the use of synthetic compounds such as aromatic amines, herbicides, pesticides, dyes and etc., in different industries is necessary and the undesirable discharge of persistent waste xenobiotic materials is unavoidable. Chlorinated aromatic compounds (CACs) require special attention due to their distinct toxicity, high stability, and persistence in the environment. CACs are ubiquitous including water, soil, and air. Their presence in the environment creates serious concerns due to chronic hazards to the health and safety of humans and wildlife. It is necessary to find efficient processes for the destruction of organic pollutants, into low harmful materials or to inorganic materials. Thus, academic and industrial researchers focus on the effective methods of CACs removal that have different advantages and disadvantages. This review represents an overwiew on current techniques for removing organic chlorinated aromatic compounds in the presence (or without) of nanophotocatalysts. Physical and chemical methods of removing CAC including thermal, oxidative, reductive and microbial processes are studied in detail.