Design and Scale-Up of Diels–Alder Reactions for the Practical Synthesis of 5-Phenylbicyclo[2.2.2]oct-5-en-2-one

Rapid access to indole-fused bicyclo[2.2.2]octanones by merging the umpolung strategy and molecular iodine as a green catalyst

One-pot synthesis of indole-fused bicyclo[2.2.2]octanones from DiMeOIN and 2-cyclohexen-1-one is accomplished under an iodine catalyst. The simple and metal-free conditions provide a practical tool to construct Csp3-rich complex molecules via coupling cyclization.

Deeper Insight into the Six-Step Domino Reaction of Aldehydes with Malononitrile and Evaluation of Antiviral and Antimalarial Activities of the Obtained Bicyclic Products

The straightforward and efficient synthesis of complex aza‐ and carbobicyclic compounds, which are of importance for medicinal chemistry, is a challenge for modern chemical methodology. An unprecedented metal‐free six‐step domino reaction of aldehydes with malononitrile was presented in our previous study to provide, in a single operation, these bicyclic nitrogen‐containing molecules. Presented here is a deeper investigation of this atom‐economical domino process by extending the scope of aldehydes, performing post‐modifications of domino products, applying bifunctional organocatalysts and comprehensive NMR studies of selected domino products. The thermodynamic aspects of the overall reaction are also demonstrated using DFT methods in conjunction with a semi‐empirical treatment of van der Waals interactions. Furthermore, biological studies of seven highly functionalized and artemisinin‐containing domino products against human cytomegalovirus (HCMV) and Plasmodium falciparum 3D7 are presented. Remarkably, in vitro tests against HCMV revealed five domino products to be highly active compounds (EC₅₀ 0.071–1.8 μm), outperforming the clinical reference drug ganciclovir (EC₅₀ 2.6 μm). Against P. falciparum 3D7, three of the investigated artemisinin‐derived domino products (EC₅₀ 0.72–1.8 nm) were more potent than the clinical drug chloroquine (EC₅₀ 9.1 nm).

Synthesis of Ethano-Bridged Diazapolycenes as Potential Precursors for Diazapolycenes and Their Properties

A series of ethanodiazapolycenes were prepared in 87%-89% yields by Friedländer reactions of three o-aminoarenecarbaldehydes with bicyclo[2.2.2]octane-2,5-dione and their spectral, thermal, and structural properties were studied. Subsequent attempts to convert them to diazapolycenes have proved unsuccessful.

Masked Ketenes as Dienophiles in the Diels–Alder Reaction

The Diels–Alder reaction is one of the most powerful, well-established, and versatile reactions in organic chemistry; however, its application in certain settings remains a challenge as a result of functional group incompatibility. In this review, we examine the methods in which masked ketenes can be employed as dienophiles, taking particular note of applications in complex settings.

2-Methyltetrahydrofuran (2-MeTHF): a biomass-derived solvent with broad application in organic chemistry

2-Methyl-tetrahydrofuran (2-MeTHF) can be derived from renewable resources (e.g., furfural or levulinic acid) and is a promising alternative solvent in the search for environmentally benign synthesis strategies. Its physical and chemical properties, such as its low miscibility with water, boiling point, remarkable stability compared to other cyclic-based solvents such as THF, and others make it appealing for applications in syntheses involving organometallics, organocatalysis, and biotransformations or for processing lignocellulosic materials. Interestingly, a significant number of industries have also started to assess 2-MeTHF in several synthetic procedures, often with excellent results and prospects. Likewise, preliminary toxicology assessments suggest that the use of 2-MeTHF might even be extended to more processes in pharmaceutical chemistry. This Minireview describes the properties of 2-MeTHF, the state-of-the-art of its use in synthesis, and covers several outstanding examples of its application from both industry and academia.