Palladium-Catalyzed Double-Suzuki–Miyaura Reactions Using Cyclic Dibenziodoniums: Synthesis of o-Tetraaryls

Palladium-Catalyzed Triple Suzuki-Miyaura Reactions Using Cyclic (Vinyl Triflate)iodonium Salts

By using cyclic (vinyl triflate)iodonium salts, a novel triple Suzuki-Miyaura reaction was accomplished for the synthesis of polyaromatic ethylene derivatives in the presence of palladium catalysts. The reaction exhibits extensive compatibility with a wide range of readily available arylboronic acids, giving triaryl-substituted ethylenes in good yields.

Diaryliodonium Salts Enabled Arylation, Arylocyclization, and Aryl-Migration

Our research interest focusing on synthetic methodology with diaryliodonium salts, is summarized in this account. Besides employing a dual activation strategy of C-I and ortho C-H bonds, we have introduced vicinal functional groups at ortho-positions of diaryliodonium salts, in which their unique reactivities have been explored in various processes, including arylation, diarylation, cascade annulation, benzocyclization, arylocyclization, and intramolecular aryl migration. The variety of mechanisms of these reactions that involves either transition metals, especially palladium in organometallic catalysis, or transition-metal free conditions, were discussed in the context.

Synthesis of New Azetidine and Oxetane Amino Acid Derivatives through Aza-Michael Addition of NH-Heterocycles with Methyl 2-(Azetidin- or Oxetan-3-Ylidene)Acetates

In this paper, a simple and efficient synthetic route for the preparation of new heterocyclic amino acid derivatives containing azetidine and oxetane rings was described. The starting (N-Boc-azetidin-3-ylidene)acetate was obtained from (N-Boc)azetidin-3-one by the DBU-catalysed Horner-Wadsworth-Emmons reaction, followed by aza-Michael addition with NH-heterocycles to yield the target functionalised 3-substituted 3-(acetoxymethyl)azetidines. Methyl 2-(oxetan-3-ylidene)acetate was obtained in a similar manner, which was further treated with various (N-Boc-cycloaminyl)amines to yield the target 3-substituted 3-(acetoxymethyl)oxetane compounds. The synthesis and diversification of novel heterocyclic amino acid derivatives were achieved through the Suzuki-Miyaura cross-coupling from the corresponding brominated pyrazole-azetidine hybrid with boronic acids. The structures of the novel heterocyclic compounds were confirmed via ¹H-, ¹³C-, ¹⁵N-, and ¹⁹F-NMR spectroscopy, as well as HRMS investigations.

Synthesis of octagon-containing molecular nanocarbons

Nanocarbons, such as fullerenes, carbon nanotubes, and graphenes, have long inspired the scientific community. In order to synthesize nanocarbon molecules in an atomically precise fashion, many synthetic reactions have been developed. The ultimate challenge for synthetic chemists in nanocarbon science is the creation of periodic three-dimensional (3D) carbon crystals. In 1991, Mackay and Terrones proposed periodic 3D carbon crystals with negative Gaussian curvatures that consist of six- and eight-membered rings (the so-called Mackay-Terrones crystals). The existence of the eight-membered rings causes a warped nanocarbon structure. The Mackay-Terrones crystals are considered a "dream material", and have been predicted to exhibit extraordinary mechanical, magnetic, and optoelectronic properties (harder than diamond, for example). To turn the dream of having this wonder material into reality, the development of methods enabling the creation of octagon-embedding polycyclic structures (or nanographenes) is of fundamental and practical importance. This review describes the most vibrant synthetic achievements that the scientific community has performed to obtain curved polycyclic nanocarbons with eight-membered rings, building blocks that could potentially give access as templates to larger nanographenes, and eventually to Mackay-Terrones crystals, by structural expansion strategies.

Dibenzopleiadiene-embeded polyaromatics via [4 + 3] annulative decarbonylation/decarboxylation

A novel and efficient sequential cross-coupling/annulation strategy is developed to construct structurally and optoelectronically diverse class of dibezopleiadiene-embeded polyaromatics.

Copper-Catalyzed Selective Arylation of Nitriles with Cyclic Diaryl Iodonium Salts: Direct Access to Structurally Diversified Diarylmethane Amides with Potential Neuroprotective and Anticancer Activities

A novel, simple, and high-yielding approach for the preparation of diarylmethane amide derivatives has been developed by reacting cyclic diaryl iodonium salts with nitriles using CuCl as a catalyst. The procedure is efficient with high atom economy and a wide substrate range. Importantly, selective arylation of nitriles was obtained without affecting the phenyl amino/hydroxyl groups. Furthermore, two of the diarylmethane amides (3k, 3s) displayed excellent neuroprotective and anticancer activities.

Heterogeneous Pd/C-catalyzed, ligand free Suzuki-Miyaura coupling reaction furnishes new p-terphenyl derivatives

A series of new para-terphenyls derivatives have been efficiently synthesized by a ligand-free heterogeneous Pd/C-catalyzed two-fold Suzuki-Miyaura coupling reaction. Methyl 5-bromo-2-iodobenzoate was selected to react with a variety of different aryl boronic acids (2a-i). Nine new p-terphenyl derivatives (3a-i) were prepared and the structures were confirmed by several analytical techniques including infrared, spectroscopy, ¹H and ¹³C NMR spectroscopy, mass spectrometry, and in the case of compound 3 b, by X-ray diffraction method. The new derivatives were obtained in very good yields (78-91%). This synthetic facile route is envisioned to improve the preparation of p-terphenyl-based natural products.

On-surface synthesis of planar acenes via regioselective aryl-aryl coupling

The reaction of 2,2'-dibromo-biphenyl on a Ag(111) surface leads to the formation of planar acenes with a high-regioselectivity rather than nonplanar saddle-shaped tetraphenylene as the typical product in solution chemistry. The regioselective aryl-aryl coupling reaction is attributed to the hydrogen repulsion between the reactants on the confined two-dimensional surface.

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

Most of the polyvalent organoiodine compounds derive from iodoarenes, which are released in stoichiometric amounts in any reaction mediated by λ3- or λ5-iodanes. In parallel to the development of solid-supported reagents or reactions catalytic in iodine, a third strategy has emerged to address this issue in terms of sustainability. The atom-economy of transformations involving stoichiometric amounts of λ3- or λ5-iodanes, thus, has been improved by designing tandem reactions that allows for incorporating the aryl motif into the products through a subsequent one-pot nucleophilic addition or catalytic coupling reaction. This review summarizes the main achievements reported in this area.

A twist on Hellwinkel’s salt, [P(2,2′-biphenyl)2]+[P(2,2′-biphenyl)3]–

Treating PCl5 with C12H8Li2, generated from either C12H10, C12H8Br2, or C12H8I2, affords three products in different ratios depending on the source of the lithiated biphenyl. Hellwinkel’s salt [P(C12H8)2][P(C12H8)3] ([1][2]) and another product [P(C12H8)(C24H16)][P(C12H8)3] ([1′][2]) were obtained by reacting PCl5 with 2,2′-dilithiobiphenyl [Route A: 2.5 equiv.; obtained from biphenyl, n-BuLi, and TMEDA; Route B: 3.0 equiv.; obtained from 2,2′-diiodobiphenyl and n-BuLi; Route C: 4.0 equiv.; obtained from 2,2′-dibromobiphenyl and n-BuLi]. The synthesis, isolation, and characterization of the chiral spiro-compound [1′][2] and the characterization of the pentavalent phosphorane [P(C12H8)2(C12H9)] (3) are reported. The complex [1′][2] was characterized by 31P{1H} NMR spectroscopy, X-ray crystallography, and mass spectrometry. The pentavalent compound (3) was characterized by 31P{1H} NMR spectroscopy and X-ray crystallography.

Synthesis of tetraphenylene derivatives and their recent advances

The synthetic strategies towards tetraphenylene derivatives are comprehensively summarized in this review. Recent advances in the functionalized tetraphenylene skeleton for research into their structurally unique properties are described together with their potential applications.

Synthesis of Functionalized Biaryls and Poly(hetero)aryl Containing Medium-Sized Lactones with Cyclic Diaryliodonium Salts

A novel one-pot procedure is described for the transition-metal catalyzed sequential difunctionalization of diaryliodonium reagents. Reaction of commercially available anthranilic acid derivatives with readily available cyclic diaryliodonium salts followed by a Sonogashira coupling afforded various alkyne substituted biaryls in good to excellent yields. The functionalized biaryls were then utilized for the rapid and efficient one-pot synthesis of novel poly(hetero)aryl containing 10-membered lactones which are potential G-quadruplex binders and telomerase inhibitors.

Pd-Catalyzed Ligand-Free Synthesis of Arylated Heteroaromatics by Coupling of N-Heteroaromatic Bromides with Iodobenzene Diacetate, Iodosobenzene, or Diphenyliodonium Salts

An efficient method for synthesizing arylated heteroaromatics has been reported via Pd-catalyzed ligand-free cross-coupling of N-heteroaromatic bromides with iodine(III) reagents under mild conditions. Iodobenzene diacetate, iodosobenzene, and diphenyliodonium salts act as ideal arylated sources in this reaction, producing bioactive aromatic-substituted pyridines and quinolines in moderate to high yields.