The use of functional groups as internal ligands for assisting C–H functionalization, termed the chelation assisted strategy, is emerging as one of the most powerful tools for construction of C–C and C–X bonds from inert C–H bonds. However, there are various directing groups which cannot be either removed after functionalization or require some additional steps or reagents for their removal, thereby limiting the scope of structural diversity of the products, and the step and atom economy of the system. These limitations are overcome by the use of the traceless directing group (TDG) strategy wherein functionalization of the substrate and removal of the directing group can be carried out in a one pot fashion. Traceless directing groups serve as the most ideal chelation assisted strategy with a high degree of reactivity and selectivity without any requirement for additional steps for their removal. The present review overviews the use of various functional groups such as carboxylic acids, aldehydes, N-oxides, nitrones, N-nitroso amines, amides, sulfoxonium ylides and silicon tethered directing groups for assisting transition metal catalyzed C–H functionalization reactions in the last decade.

Imidazo[1,2-a]pyridine has been shown to be an important biologically active moiety. This review is a compilation of the scattered output of results of the anticancer activities of the imidazo[1,2-a]pyridine system since 2001, which have been classified as inhibition of CDK, VEGFR, PI3K, EGFR, RGGT etc. along with inhibition against different tumor cell lines. Various imidazo[1,2-a]pyridine based analogues have been used as lead molecules and are now under human clinical trials. This review will help the wider scientific community in the area of drug discovery of imidazo[1,2-a]pyridines as novel anticancer agents.

Great advances in elucidating molecular structures allow the precise determination of the interactions between a protein and a therapeutic agent. Enzyme inhibitors are used as a therapeutic agent with organic molecules, that interact with their targets through the weak linkages of hydrogen bonding and van der Waals interactions. These reduce the undesirable side effects and allow more non-specific interactions with non-target molecules. Benzimidazole acts as an enzyme inhibitor that may interact with different proteins and enzymes and has inspired chemists to carry out various structural variations of it. This review discusses the development of distinct benzimidazoles with an array of enzyme inhibitors viz., aurora kinase inhibitors, cyclin-dependent kinase inhibitors, mitogen activated protein kinase inhibitors, polo like kinase inhibitors, Tie kinase inhibitors, lymphocyte specific kinase inhibitors etc., also highlighting the molecular interaction with enzyme inhibitors. Various derivatives of benzimidazole, with different inhibitory activities, have been described on the basis of substitution around the central moiety, with an aim to help medicinal chemists to develop structure–activity relationships. The reviews in the literature till now are focused only on the biological activities of benzimidazole viz., antiviral, anticancer and antifungal, but the present review focuses on the latest work, describing the inhibitor aspects and the potential of the benzimidazole ring. This discussion will further help in the development of novel benzimidazole compounds.