Application of Multi-component Reaction in the Synthesis of Heterocyclic [3.3.3] Propellane Derivatives

Propellanes and derivatives have attractive properties due to their unique structure. Therefore, [3.3.3] propellanes, containing tricyclic structures with one of the carbon-carbon bonds common in three rings, were used in natural products, pharmaceutical compounds, and heterocyclic compounds, which were biologically important. The various multi-component reactions were applied in the synthesis of propellanes, which were highlighted throughout this review

Organocatalytic Difluorobenzylation of 1,2-Diketones via Mild Cleavage of Carbon−Carbon Bonds

α-aryl-α,α-Difluoroacetophenones (DFAPs) are developed as a new type of difluorobenzylation reagents that can be facilely prepared from readily available and cheap starting materials. In-situ carbon-carbon bond cleavage of electron-deficient DFAPs...

Synthesis of Novel 2-diethylamino-4H-7-(Het) aryl pyrido[1,2-a][1,3,5]triazin-4-ones via a Suzuki Cross-Coupling Reaction of 2-Diethylamino-4H-7-iodopyrido[1,2a][1,3,5]triazin-4-one with (Het) arylboronic Acids in Water

Suzuki cross coupling reaction is one of the most famous organic reactions of the 20th century’s chemistry. It is deemed of as one of the most famous reaction in the field of chemistry. It is a very effective method for making carbon–carbon bonds. It has been extensively utilized in the synthesis of many carbon molecules including the most complex ones.Syntheses of 2-diethylamino-4H-7-(Het) aryl pyrido [1,2-a] [1,3,5] triazin-4-ones are currently under investigation in order to obtain great potentialities in medicinal chemistry of compounds class. The methodology we propose herein is able to produce numerous 2-diethylamino-4H-7-(Het)arylpyrido[1,2-a][1,3,5]triazin-4-one and derivatives that were synthesized, purified and characterized by 1HNMR, 13CNMR, MS techniques. Furthermore, it allows sequential introduction of various substituents into a 2-alkylylamino-4H-7-(Het)arylpyrido[1,2-a][1,3,5]triazin-4-ones ring using a one-pot procedure. The biological evaluation as well as the physico-chemical characterisation of various products are currently under way and will be described elsewhere.

Structural Basis for an Unprecedented Enzymatic Alkylation in Cylindrocyclophane Biosynthesis

The cyanobacterial enzyme CylK assembles the cylindrocyclophane natural products by performing two unusual alkylation reactions, forming new carbon-carbon bonds between aromatic rings and secondary alkyl halide substrates. This transformation is unprecedented in biology and the structure and mechanism of CylK are unknown. Here, we report x-ray crystal structures of CylK, revealing a distinctive fusion of a Ca2+ binding domain and a β-propeller fold. We use a mutagenic screening approach to locate CylK’s active site at its domain interface, identifying two residues, Arg105 and Tyr473, that are required for catalysis. Anomalous diffraction datasets collected with bound bromide ions, a product analog, suggest these residues interact with the alkyl halide electrophile. Additional mutagenesis and molecular dynamics simulations implicates Asp440 and Glu374 in activating the nucleophilic aromatic ring. Bioinformatic analysis of CylK homologs from other cyanobacteria establishes that they conserve these key catalytic amino acids but they are likely associated with divergent reactivity and altered secondary metabolism. By gaining a molecular understanding of this unusual biosynthetic transformation, this work fills a gap in our understanding of how alkyl halides are activated and used by enzymes as biosynthetic intermediates, informing enzyme engineering, catalyst design, and natural product discovery.

Applications of Photoredox Catalysis for the Radical-Induced Cleavage of C-C Bonds

Selective cleavage of C-C bonds forms one of the greatest challenges in current organic chemistry, due to the relative strength of these bonds. However, such transformations are an invaluable instrument to break down and construct new carbon-carbon bonds. To achieve this, photochemistry can be used as a valuable tool to generate radicals and induce the cleavage of these bonds. This review paints a picture of some of the most influential contributions in this field from the last decade.

The Response of Electronic And Energetic Properties of Two Types of The Sp-hybridised Carbon-Carbon Bonds To An External Uniform Electric Field

The susceptibility of electronic and energetic properties of two sets of molecules to perturbation in a uniform electric field was investigated. The molecules of one set were (10)cumulenes terminated with two functional groups, R1 and R2; those of the second set were (10)polyyenes substituted with the same R1 and R2 groups. The cumulene and polyyne molecules had similar lengths of the system of conjugated bonds between the two most extreme carbon atoms. Dipole moments and polarizabilities of the molecules were used as determinants of the overall charge transfer between polar groups and their modifications due to the application of an external electric field. The field was directed along the main (longest) axis of the molecules from the negative to the positive pole. Comparison of the polarizability values revealed that they were higher in the (10)cumulenes than in the (10)polyynes. Parabolic dependence of the molecular energy as function of field strength can be interpreted in terms of the response of electron density to an electric field.

High Density Polyethylenes Bearing Isolated In-Chain Carbonyls

Polyethylene materials are highly important polymers which are produced in the largest volume among all plastics. Due to the chemical inert property of saturated carbon-carbon bonds, the degradation of polyethylene is extremely challenging, which prevents them from efficient chemical recycling. Installing functional groups in the main chain of polyethylenes may facilitate the degradation and following chemical recycling of polyethylene materials. Here we report a highly selective approach for the synthesis of high-density polyethylenes bearing isolated in-chain carbonyls. Linear high-molecular weight polyethylene chains are synthesized via the palladium catalyzed copolymerization of ethylene with metal carbonyls. Different from traditional ethylene/CO copolymerization reactions, excellent non-alternating selectivity has been achieved. While the properties of polyethylene have been retained in the copolymer, faster degradation compared with that of polyethylene was observed upon UV light irradiation. The synthesized materials may therefore serve as more environmentally friendly alternative plastics than traditional polyethylene materials.

Palladium-Catalyzed Dehydrogenative C-2 Alkenylation of 5-Arylimidazoles and Related Azoles with Styrenes

The construction of carbon–carbon bonds by direct involvement of two unactivated carbon–hydrogen bonds, without any directing group, ensures a high atom economy of the entire process. Here, we describe a simple protocol for the Pd(II)/Cu(II)-promoted intermolecular cross-dehydrogenative coupling (CDC) of 5-arylimidazoles, benzimidazoles, benzoxazole and 4,5-diphenylimidazole at their C-2 position with functionalized styrenes. This specific CDC, known as the Fujiwara–Moritani reaction or oxidative Heck coupling, also allowed the C-4 alkenylation of the imidazole nucleus when both 2 and 5 positions were occupied.

A platform for on-the-complex annulation reactions with transient aryne intermediates

Organometallic complexes are ubiquitous in chemistry and biology. Whereas their preparation has historically relied on ligand synthesis followed by coordination to metal centers, the ability to efficiently diversify their structures remains a synthetic challenge. A promising yet underdeveloped strategy involves the direct manipulation of ligands that are already bound to a metal center, also known as chemistry-on-the-complex. Herein, we introduce a versatile platform for on-the-complex annulation reactions using transient aryne intermediates. In one variant, organometallic complexes undergo transition metal-catalyzed annulations with in situ generated arynes to form up to six new carbon–carbon bonds. In the other variant, an organometallic complex bearing a free aryne is generated and intercepted in cycloaddition reactions to access unique scaffolds. Our studies, centered around privileged polypyridyl metal complexes, provide an effective strategy to annulate organometallic complexes and access complex metal–ligand scaffolds, while furthering the synthetic utility of strained intermediates in chemical synthesis.