Metal-free and atom-efficient protocol for diarylation of selenocyanate by diaryliodonium salts

We developed an atom- and reaction mass efficient strategy for the preparation of diarylselenides using iodonium salts as reactants. The developed approach allows the obtaining of diarylselenides from the corresponding trimethoxyphenyl-substituted iodonium salts via a two-step one-pot reaction sequence. The proposed metal-free methodology is based on the involvement of both iodonium aryl groups for diarylation.

Electrochemical Synthesis of Dibenzothiophenes via Intramolecular C-S Cyclization with a Halogen Mediator

Electrochemical synthesis of dibenzothiophene derivatives was achieved. Several bis(biaryl) disulfides are efficiently converted to dibenzothiophenes by electrochemical oxidation. The use of Bu4NBr as a halogen mediator was essential, and wide varieties of dibenzothiophene derivatives were obtained in good yields.

One-Pot Synthesis of Heteroatom-Bridged Cyclic Diaryliodonium Salts

Two one-pot procedures for the construction of O- and N-bridged diaryliodonium triflates are described. An effective aryne-mediated arylation of o-iodophenols and -sulfonamides provides diarylether and diarylamine intermediates, which are subsequently oxidized and cyclized to the corresponding diaryliodaoxinium and -iodazinium salts. Different derivatizations were applied to demonstrate their capacity as useful building blocks and gain a deeper understanding toward the general reactivity of these underdeveloped but potentially highly useful compounds.

Iodolium salts as halogen-bond donor catalysts in the Nazarov cyclization: the molecular oxygen enigma

Nazarov cyclizations of activated precurosrs are achieved under iodolium catalysis, provided that oxygen is present for catalyst activation and turnover.

Facile Synthesis of Thienoacenes via Transition-Metal-Free Ladderization

Herein, we report a facile transition-metal-free approach to sulfur-containing heteroacenes from fluorinated oligophenylenes. Unlike most existing methods, the presented approach is not restricted to simple dibenzothiophene derivatives and thus appears to be a useful tool for the synthesis of extended sulfur-containing heteroacenes. The incorporation of sulfur is unambiguously preprogrammed via the positions of fluorines in the precursors, allowing the selective synthesis of extended thienoacenes with up to 96% yield.

Preparation and Synthetic Applicability of Imidazole-Containing Cyclic Iodonium Salts

A novel approach to the preparation of imidazole-substituted cyclic iodonium salts has been developed via the oxidative cyclization of 1-phenyl-5-iodoimidazole using a cheap and available Oxone/H₂SO₄ oxidative system. The structure of the new polycyclic heteroarenes has been confirmed by single-crystal X-ray diffractometry, revealing the characteristic structure features for cyclic iodonium salts. The newly produced imidazole-flanked cyclic iodonium compounds were found to readily engage in a heterocyclization reaction with elemental sulfur, affording benzo[5,1-b]imidazothiazoles in good yields.

Cu-Catalyzed tandem N-arylation of phthalhydrazides with cyclic iodoniums to yield dihydrobenzo[c]cinnolines

Dihydrocinnolines have significant pharmacological properties. Herein, we investigate a Cu-catalyzed tandem N-arylation reaction of phthalhydrazides with cyclic iodonium salts to construct dihydrobenzo[c]cinnoline derivatives. Various iodonium salts, such as symmetrical, unsymmetrical, aryl-aryl, and aryl-heteroaryl ones, could react with phthalhydrazides smoothly and give the title products in moderate to high yields. Moreover, the -NH2 group, which has been diarylated by cyclic iodonium salts to form carbazoles in previous reports, is also well tolerated in this work.

Bifunctional reagents in organic synthesis

Developments in synthetic chemistry are increasingly driven by improvements in the selectivity and sustainability of transformations. Bifunctional reagents, either as dual coupling partners or as a coupling partner in combination with an activating species, offer an atom-economic approach to chemical complexity, while suppressing the formation of waste. These reagents are employed in organic synthesis thanks to their ability to form complex organic architectures and empower novel reaction pathways. This Review describes several key bifunctional reagents by showcasing selected cornerstone research areas and examples, including radical reactions, C-H functionalization, cross-coupling, organocatalysis and cyclization reactions.

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.

One-Pot Synthesis and Conformational Analysis of Six-Membered Cyclic Iodonium Salts

Two one-pot procedures for the construction of carbon-bridged diaryliodonium triflates and tetrafluoroborates are described. Strong Brønsted acids enable the effective Friedel-Crafts alkylation with diversely substituted o-iodobenzyl alcohol derivatives, providing diphenylmethane scaffolds, which are subsequently oxidized and cyclized to the corresponding dibenzo[b,e]iodininium salts. Based on NMR investigations and density functional theory (DFT) calculations, we could verify the so-far-undescribed existence of two stable isomers in cyclic iodonium salts substituted with aliphatic side chains in the carbon bridge.

Transition-metal mediated carbon-sulfur bond activation and transformations: an update

Carbon-sulfur bond cross-coupling has become more and more attractive as an alternative protocol to establish carbon-carbon and carbon-heteroatom bonds. Diverse transformations through transition-metal-catalyzed C-S bond activation and cleavage have recently been developed. This review summarizes the advances in transition-metal-catalyzed cross-coupling via carbon-sulfur bond activation and cleavage since late 2012 as an update of the critical review on the same topic published in early 2013 (Chem. Soc. Rev., 2013, 42, 599-621), which is presented by the categories of organosulfur compounds, that is, thioesters, thioethers including heteroaryl, aryl, vinyl, alkyl, and alkynyl sulfides, ketene dithioacetals, sulfoxides including DMSO, sulfones, sulfonyl chlorides, sulfinates, thiocyanates, sulfonium salts, sulfonyl hydrazides, sulfonates, thiophene-based compounds, and C[double bond, length as m-dash]S functionality-bearing compounds such as thioureas, thioamides, and carbon disulfide, as well as the mechanistic insights. An overview of C-S bond cleavage reactions with stoichiometric transition-metal reagents is briefly given. Theoretical studies on the reactivity of carbon-sulfur bonds by DFT calculations are also discussed.

Copper-catalyzed diastereoselective hydrothioetherification of oxa(aza)benzonorbornadienes

A novel copper-catalyzed hydrothioetherification of oxa(aza)bicyclic alkenes with potassium thioacetate and aryl or alkyl iodides to synthesize unsymmetrical thioethers has been developed. Notably, the reaction with complete diastereoselectivity went through a syn-selective addition process to give exo-adducts. In addition, this protocol exhibited high efficiency and good functional group tolerance to afford the target thioethers in moderate to good yields. Based on the results of mechanistic investigations, a plausible mechanism was proposed.

Construction of 2,3-disubstituted benzo[b]thieno[2,3-d]thiophenes and benzo[4,5]selenopheno[3,2-b]thiophenes using the Fiesselmann thiophene synthesis

A series of 3-(hetero)aryl-substituted benzo[b]thieno[2,3-d]thiophenes, bearing various electron withdrawing groups at C-2 position of their scaffolds, were obtained using a convenient approach based on the Fiesselmann thiophene synthesis. To realize this strategy, the Friedel-Crafts acylation of (hetero)arenes with easily accessible 3-chlorobenzo[b]thiophene-2-carbonyl chlorides was initially performed to afford 3-chloro-2-(hetero)aroylbenzo[b]thiophenes. The latter ketones were treated either with methyl thioglycolate in the presence of DBU and calcium oxide powder or successively with sodium sulfide, an alkylating agent, containing methylene active component, and also DBU and calcium oxide, to form the desired benzo[b]thieno[2,3-d]thiophene derivatives. In addition, similar benzo[4,5]selenopheno[3,2-b]thiophene derivatives were prepared in the same manner using 3-bromobenzo[b]selenophen-2-yl substrates. The obtained functional derivatives of both benzo[b]thieno[2,3-d]thiophene and benzo[4,5]selenopheno[3,2-b]thiophene are of interest for further elaboration of organic semiconductor materials.

Palladium-Catalyzed Direct Mono- or Polyhalogenation of Benzothiadiazole Derivatives

An unprecedented method for the palladium (II)-catalyzed direct halogenation of benzothiadiazole derivatives is reported here, which would allow the rational tuning of their electronic properties by further transformations. The key strategy is the combination of the double functions of benzothiadiazole as both an important moiety of functional materials and modifiable directing group. Various mono/polychlorinated, brominated, or iodinated benzothiadiazole products could be prepared efficiently, which can be converted into a wide range of valuable polyaromatic compounds with potential applications in material chemistry.

Domino N-/C- or N-/N-/C-arylation of imidazoles to yield polyaryl imidazolium salts via atom-economical use of diaryliodonium salts

Herein, we disclose a Cu-mediated domino di-/triarylation reaction of imidazoles to efficiently access polyaryl imidazolium salts in a single step by using two aryls as well as an anion of a diaryliodonium salt. The diarylation shows high atom economy and excellent selectivity with unsymmetrical iodonium salts.

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.

Construction of Functionalized Annulated Sulfone via SO2/I Exchange of Cyclic Diaryliodonium Salts

A straightforward protocol for diarylannulated sulfone construction is efficiently established via SO₂/I exchange of iodonium(III) salts. Readily available inorganic Na₂S₂O₅ was served as a safe and convenient SO₂ surrogate. Diverse functionalized diarylannulated sulfones were smoothly achieved in good to excellent yields with great functional group compatibility. Organic light emitting diodes (OLEDs) material molecules were subsequently established via this method in gram scale. The unsymmetrical conjugated systems with donor-acceptor groups and π-conjugation bridges motifs, which substantially communicate electron mobility in semiconductor material molecules, were successfully afforded under the facile conditions of the exchange strategy.

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.

Cu(ii)-catalyzed sulfide construction: both aryl groups utilization of intermolecular and intramolecular diaryliodonium salt

A sulfur–iodine exchange strategy was developed that utilized both aryl groups of diaryliodonium salt employed in intermolecular and intramolecular reactions.

Iodine-doped sumanene and its application for the synthesis of chalcogenasumanenes and silasumanenes

The first example of halogen-doped buckybowls has been synthesized, which can be readily transformed into pristine trithiasumanene, triselenasumanene and trisilasumanene.