Explore the vast range of titles available.

Two new series of heterocyclic derivatives with potential anticancer activity, in which a pyrrolo[1,2-b]pyridazine or a pyrrolo[2,1-a]phthalazine moiety was introduced in place of the 3′-hydroxy-4′-methoxyphenyl ring of phenstatin have been synthesised and their structure-activity relationship (SAR) was studied. Fourteen of the new compounds were evaluated for their in vitro cytotoxic activity by National Cancer Institute (NCI) against 60 human tumour cell lines panel. The best five compounds in terms of in vitro growth inhibition were screened in the second stage five dose-response studies, three of them showing a very good antiproliferative activity with GI 50 <100 nM on several cell lines including colon, ovarian, renal, prostate, brain and breast cancer, melanoma and leukemia. Docking experiments on the biologically active compounds showed a good compatibility with the colchicine binding site of tubulin.

Indole, a ubiquitous and structurally versatile aromatic compound, has emerged as a key player in the synthesis of diverse heterocyclic frameworks via cycloaddition reactions. These reactions are completely atom-economical and, hence, are considered as green reactions. This review article provides a comprehensive overview of the pivotal role played by indole in the construction of complex and biologically relevant heterocyclic compounds. Here we explore the chemistry of indole-based cycloadditions, highlighting their synthetic utility in accessing a wide array of heterocyclic architectures, including cyclohepta[b]indoles, tetrahydrocarbazoles, tetrahydroindolo[3,2-c]quinoline, and indolines, among others. Additionally, we discuss the mechanistic insights that underpin these transformations, emphasizing the strategic importance of indole as a building block. The content of this article will certainly encourage the readers to explore more work in this area.

The present review narrates several reports which deal with the synthesis of fused 1,2,3-triazole containing scaffolds following a sequential multicomponent reaction (MCR)—intramolecular azide-alkyne cycloaddition (IAAC) approach. The reviewed reactions were cleverly designed so as to incorporate azide and alkyne functionalities in the MCR product which was then subjected to IAAC. The review is divided into two sections based on the number of components in the multicomponent reaction. We have aimed at a critical discussion and also have highlighted either advantages or disadvantages of each methodology.

3H-1,2-Dithiole-3-thiones are among the best studied classes of polysulfur-containing heterocycles due to the almost explosive recent interest in these compounds as sources of hydrogen sulfide as an endogenously produced gaseous signaling molecule. This review covers the recent developments in the synthesis of these heterocycles, including both well-known procedures and important novel transformations for building the 1,2-dithiole-3-thione ring. Diverse ring transformations of 3H-1,2-dithiole-3-thiones into various heterocyclic systems through 1,3-dipolar cycloaddition, replacement of one or two sulfur atoms to form carbon- and carbon-nitrogen containing moieties, and other unexpected reactions are considered.

The present review contains a representative sampling of mechanistic studies, which have appeared in the literature in the last 5 years, on 1,3-dipolar cycloaddition reactions, using DFT calculations. Attention is focused on the mechanistic insights into 1,3-dipoles of propargyl/allenyl type and allyl type such as aza-ylides, nitrile oxides and azomethyne ylides and nitrones, respectively. The important role played by various metal–chiral–ligand complexes and the use of chiral eductors in promoting the site-, regio-, diastereo- and enatioselectivity of the reaction are also outlined.

We have streamlined a dipolar cycloaddition approach to assemble the core of malayamycin A and other related uracil nucleosides possessing the common bicyclic perhydrofuropyran framework. The latent functionality strategy employing oxazoline to unmask the 1,2-hydroxyamine moiety proves feasible, eliminating the need for alkene functionalization required in previous endeavours. This current strategy provides a reliable platform for accessing diverse uracil nucleosides and their derivatives, facilitating the development of potent fungicides.

Diphenylethylenediamine‐derived imidazoline‐amino acid derivatives are designed as nonphosphine chiral nitrogen ligands for metal‐catalyzed exo‐selective [3 + 2] cycloaddition reaction of iminoesters with nitroalkenes. The newly developed (R,R)‐imidazoline‐L‐proline and t‐butyl prolinate‐Cu(OTf)2 complexes afford the exo‐pyrrolidine adducts with up to 99% ee. From a modular synthesis of nonphosphine chiral nitrogen‐based chiral imidazoline–amino acid ligands, two new chiral imidazoline–proline‐copper catalysts are developed for targeting exo‐selective [3 + 2] cycloaddition reaction. Density functional theory studies rationalize the observed stereoselectivity and the distinct chiral pockets of the two catalysts account for their different substrate compatibility.

The development of novel synthons and efficient methods to synthesize chiral polycyclic indoles has been a hot topic in organic synthesis and medicinal chemistry owing to their broad applications in medicines, pesticides, and other functional molecules. Here, we disclosed novel indolyl substituted metal-allyl zwitterionic intermediates through the decarboxylation of conveniently available vinyl indoloxazolidones, which could be regarded as two types of dipolar species through the anionic delocalization. The palladium-π-allyl species tended to serve as an all-carbon 1,3-dipole in the asymmetric [3+2] cycloaddition with electron-deficient alkenes, which furnished polysubstituted cyclopenta[ b ]indoles with high regio- and stereoselectivities. Meanwhile, the iridium-π-allyl species was recognized as an aza-1,3-dipole in asymmetric [3+2] cycloaddition with in situ generated C1 ammonium enolates, affording pyrrolo[1,2- a ]indoles with high diastereo- and enantioselectivities. In addition, the dipolar cycloadditions could be easily scaled-up and several synthetic transformations of the cycloadducts were demonstrated for the rapid synthesis of diverse chiral polycyclic indoles.

The 1,3‐dipolar cycloaddition reactions (DCs) of nitrile oxides (NOs) to alkenes and alkynes are useful methods for the synthesis of 2‐isoxazolines and isoxazoles respectively, which are important classes of heterocyclic compounds in organic and medicinal chemistry. Most of these reactions are carried out in organic solvents and under thermal activation. Nevertheless the use of supercritical carbon dioxide (scCO2) and ionic liquids (Ils) as alternative solvents and the application of microwave (MW) and ultrasound (US) as alternative activation procedures have evident advantages from the “Green Chemistry” point of view. The critical discussion on the applications of these “unconventional” activation methods and reaction conditions in the 1,3‐DCs of NOs is the objective of the present Review. Unconventional but sustainable: Reactions that use nitrile oxides (NOs) as 1,3‐dipoles play an important role in the group of reactions defined as 1,3‐dipolar cycloadditions (1,3‐DC, Huisgen reactions). From the point of view of sustainable (green) chemistry, the use of some “unconventional” solvents (supercritical carbon dioxide and ionic liquids) and activation procedures (microwave and ultrasound irradiation) in these reactions are an appealing challenge.This Review presents a critical discussion on the applications of these procedures in the 1,3‐DC reactions of NOs.

The 1,4-dipolar cycloaddition of the ylidene derivative of 1H-pyrrole-2,3-dione to a dipole generated in situ from 1-benzylbenzimidazole and dimethyl acetylenedicarboxylate proceeds via the exocyclic multiple bond of the ylidene derivative and affords a mixture of diastereomeric spiro[benzo[4,5]imidazo[1,2-a]pyridine-3,3’-pyrroles], which slowly epimerized in a solution.