Three-component coupling of arynes, aminosilanes, and aldehydes

A three-component coupling of arynes, aminosilanes, and aldehydes enables diverse amino and hydroxymethyl groups to be incorporated directly into 1,2-positions of aromatic rings.     

Three-component coupling using arynes and DMF: straightforward access to coumarins via ortho-quinone methides

ortho-Quinone methides, arising from a formal [2+2] cycloaddition between arynes and DMF, were found to facilely undergo a [4+2] cycloaddition with ester enolates or ketenimine anions to produce diverse coumarins in a straightforward manner.     

Three-component coupling using arynes and isocyanides: straightforward access to benzo-annulated nitrogen or oxygen heterocycles

A variety of aldehydes, ketones, benzoquinones, or sulfonylimines were found to couple with arynes and isocyanides, giving iminodihydroisobenzofuran or iminoisoindoline derivatives of structural diversity in a straightforward manner. Nucleophilic addition of isocyanides to arynes, a first step of the three-component coupling, was proved to be reversible by the reaction of an unsymmetrical aryne.     

Aminosilylation of arynes with aminosilanes: synthesis of 2-silylaniline derivatives

The nitrogen-silicon sigma-bond of aminosilanes added across the triple bond of arynes to give varied 2-silylaniline derivatives straightforwardly.     

Palladium-catalyzed ortho-selective C–H bond chlorination of aromatic ketones

A palladium-catalyzed ortho-selective C–H bond chlorination reaction for the preparation of 2-chloro aromatic ketones was described. Both electron-withdrawing and electron-donating groups on the aromatic rings are well tolerated under the optimized conditions. The 2-chloro aromatic ketones obtained by our method could be applied to synthesize the derivatives of 1H-indazole or benzo[d]isoxazole.     

Three-component cascade energy transfer with use of oligonaphthalene skeletons

Three oligonaphthalenes with zinc porphyrin and free-base porphyrin moieties were synthesized, in which cascade energy transfer (from naphthalene to free-base porphyrin via zinc porphyrin) was observed when the zinc and free-base porphyrins were close to each other.     

Nitrogen-directed ortho-selective homocoupling of aromatic compounds catalyzed by ruthenium complexes

A nitrogen-directed regioselective homocoupling reaction of aromatic compounds has been found to be catalyzed by a ruthenium complex in the presence of methallyl acetate as a hydrogen scavenger.     

Synthesis of dye functionalized xerogels via nucleophilic aromatic substitution of fluoro aromatic compounds with aminosilanes

The one-pot synthesis of inorganic–organic hybrid materials via combination of sol–gel process and nucleophilic aromatic substitution reaction of various fluoro aromatic compounds and 3-aminopropyltrimethoxysilane has been studied. Both, nucleophilic aromatic substitution reaction and sol–gel process can be accomplished in the same reaction vessel due to the sol–gel precursor tetraethoxysilane acting as solvent during the first reaction step. Hydrogen fluoride, which forms as a by-product of the substitution reaction, is trapped by both silane species present and subsequently serves as catalyst during the sol–gel process. The obtained materials can be classified as type II xerogels, because of the covalent linkage between organic chromophor and inorganic silicon network. Fluoro aromatic compounds with different reactivities for nucleophilic aromatic substitution reactions containing azo, azomethine, and diphenylamine groups were used in order to (1) demonstrate the synthetic concept and (2) fine-tune the optical properties of the resulting chromophoric xerogels. The final chromophor content within the xerogels was varied by modifying the ratio of organosilicon precursor and tetraethoxysilane. All obtained organic–inorganic hybrid materials were characterized in detail using solid state NMR- and UV/vis spectroscopy. Latter one gave experimental confirmation of the partial hydrolysis of azomethine dyes in the xerogels, while no decomposition of azo or diphenylamine dyes was observed.     

Three-component coupling sequence for the regiospecific synthesis of substituted pyridines

A de novo synthesis of substituted pyridines is described that proceeds through nucleophilic addition of a dithiane anion to an α,β-unsaturated carbonyl followed by metallacycle-mediated union of the resulting allylic alcohol with preformed trimethylsilane-imines (generated in situ by the low-temperature reaction of lithium hexamethyldisilazide with an aldehyde) and Ag(I)- or Hg(II)-mediated ring closure. The process is useful for the convergent assembly of di- through penta-substituted pyridines with complete regiochemical control.     

Synthesis of benzisoxazolines by the coupling of arynes with nitrones

A variety of substituted benzisoxazolines have been synthesized by the [3 + 2] cycloaddition of nitrones and arynes. The reaction scope is broad, the reaction conditions are mild, and the process tolerates a variety of functional groups.     

Copper-catalyzed three-component coupling of arynes, terminal alkynes and activated alkenes

The three-component coupling of benzynes with terminal alkynes and activated alkenes in the presence of CuI, PCy(3) and CsF in a 1:1 mixture of CH(3)CN and THF at 50 degrees C for 5 h gave 1-alkyl-2-alkynylbenzenes in good to moderate yields.     

Three-component coupling of benzyne: domino intermolecular carbopalladation

A new three-component coupling reaction of benzyne is described that uses two intermolecular carbopalladation reactions to produce 1,2-functionalized benzene derivatives.     

Amine and nitramine functionalization of imidazole-triazine and triazole-triazine skeletons: Exploring for potential multipurpose energetic materials

A series of five and six-membered C-C bonded energetic materials ( 2 – 7 ) based on a combination of imidazole-triazine and triazole-triazine backbones were designed, synthesized, and characterized using NMR, IR, Mass spectrometry, and TGA-DSC studies. Further, the structure of compound 4 was supported by single-crystal X-ray analysis. All the newly synthesized energetic compounds exhibit good density, excellent thermal stability, good detonation performance, and low mechanical sensitivity toward impact and friction. Among all, the nitrate salt 4 exhibits balanced properties, including high density (1.80 g cm⁻³), excellent thermal stability (254°C), good detonation velocity (8178 m s⁻¹), and low sensitivity towards impact and friction. The facile synthetic feasibility, thermal stability, energetic performance, and insensitivity of all the molecules suggest they can be used as an insensitive secondary explosive in various defense and civilian applications.     

Bioconjugate functionalization of thermally carbonized porous silicon using a radical coupling reaction

The high stability of Salonen's thermally carbonized porous silicon (TCPSi) has attracted attention for environmental and biochemical sensing applications, where corrosion-induced zero point drift of porous silicon-based sensor elements has historically been a significant problem. Prepared by the high temperature reaction of porous silicon with acetylene gas, the stability of this silicon carbide-like material also poses a challenge--many sensor applications require a functionalized surface, and the low reactivity of TCPSi has limited the ability to chemically modify its surface. This work presents a simple reaction to modify the surface of TCPSi with an alkyl carboxylate. The method involves radical coupling of a dicarboxylic acid (sebacic acid) to the TCPSi surface using a benzoyl peroxide initiator. The grafted carboxylic acid species provides a route for bioconjugate chemical modification, demonstrated in this work by coupling propylamine to the surface carboxylic acid group through the intermediacy of pentafluorophenol and 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC). The stability of the carbonized porous Si surface, both before and after chemical modification, is tested in phosphate buffered saline solution and found to be superior to either hydrosilylated (with undecylenic acid) or thermally oxidized porous Si surfaces.     

C-C bond formation via double C-H functionalization: aerobic oxidative coupling as a method for synthesizing heterocoupled biaryls

The aerobic oxidative coupling of arenes such as benzofuran and N-substituted indoles with benzene and derivatives thereof is described. The reaction is shown to take place in both inter- and intramolecular scenarios.     

Polymer support assisted selective functionalization of azoles using a palladium-catalyzed coupling reaction

Regioselective palladium-catalyzed monoarylation of azoles was achieved using iodobenzoate immobilized on an insoluble polymer support. The positional selectivity for the coupling reaction was dramatically influenced by the presence of CuI. No diarylation was observed in either case. Unsymmetrical diarylation was also obtained with the polymer support using sequential coupling reactions.     

Fused multifunctionalized bridge aromatic hydrocarbons from in situ-generated arynes and anthracene derivatives

This study presents a facile strategy for the formation of highly substituted butterfly 1,4-adducts/9,10-adducts via the Diels–Alder reaction of benzyne intermediates. The method achieves very good to excellent yields of the respective anthracene derivatives under mild conditions. This practical protocol is compatible with a variety of sensitive functional groups and provides access to difunctionalized bridge 1,4-adducts/9,10-adducts.     

Additive-free clicking for polymer functionalization and coupling by tetrazine-norbornene chemistry

Herein we report the use of a tetrazine-norbornene inverse electron demand Diels-Alder conjugation applied to polymer end-functionalization and polymer-polymer coupling. The reaction was found to be applicable to polymer-polymer coupling, as judged by SEC, DOSY NMR, and LCxSEC analyses, giving diblock copolymers by merely mixing the constituent homopolymers together under ambient conditions, using no catalyst, additive, or external stimulus.     

Three-component condensation of α-nitroacetophenone,aromatic aldehydes,and methylurea

The three-component condensation of aromatic aldehydes, methylurea, and α-nitroacetophenone affords both N(1)-and N(3)-methyl-substituted 4,6-diaryl-5-nitro-3,4-dihydropyrimidin-2(1H)-ones depending on the structure of aldehyde. Intermediate 4,6-diaryl-4-hydroxy-3-methyl-5-nitrohexahydropyrimidin-2-ones and trisubstituted urea, which is the transformation product of the 4-hydroxy-3-methyl derivative in an acidic medium (retro-Henry reaction), were identified in the reaction mixtures. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1141–1145, June, 2007.