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The area of catalysis of radical reactions has recently flourished. Various reaction conditions have been discovered and explained in terms of catalytic cycles. These cycles rarely stand alone as unique paths from substrates to products. Instead, most radical reactions have innate chains which form products without any catalyst. How do we know if a species added in "catalytic amounts" is a catalyst, an initiator, or something else? Herein we critically address both catalystfree and catalytic radical reactions through the lens of radical chemistry. Basic principles of kinetics and thermodynamics are used to address problems of initiation, propagation, and inhibition of radical chains. The catalysis of radical reactions differs from other areas of catalysis. Whereas efficient innate chain reactions are difficult to catalyze because individual steps are fast, both inefficient chain processes and non-chain processes afford diverse opportunities for catalysis, as illustrated with selected examples. [ABSTRACT FROM AUTHOR]

In the context of modular and rapid construction of molecular diversity and complexity for applications in organic synthesis, biomedical and materials sciences, a generally useful strategy has emerged based on boron-selective chemical transformations. In the last decade, these types of reactions have evolved from proof-of-concept to some advanced applications in the efficient preparation of complex natural products and even automated precise manufacturing on the molecular level. These advances have shown the great potential of boron-selective reactions in simplifying synthetic design and experimental operations, and should inspire new developments in related chemical and technological areas. This tutorial review will highlight the original contributions and representative advances in this emerging field. [ABSTRACT FROM AUTHOR]

Methods of aryl(hetaryl)-substituted gem-cyanonitroethenes preparation are summarized, and the products structure elucidation by means of H, C NMR, IR, and UV spectroscopy methods is discussed. E-Configuration of the compounds obtained has been proved. Reaction of the studied gem-cyanonitroethenes with 2,3-dimethyl-1,3-butadiene affords the diene synthesis adducts-6-aryl(hetaryl)-3,4-dimethyl-1-nitro-1-cyano- 3-cyclohexenes. [ABSTRACT FROM AUTHOR]

Reaction of N-[chloro(methylvinyl)silyl]-, N-[chloro(methylphenyl)silyl]anilines and of N-[chloro- (methylvinyl)silyl]-, N-[chloro(methylphenyl)silyl]- N-methylanilines with isopropylamine and isopropanol yielding the products of chlorine substitution with isopropoxy and isopropylamino group, respectively, has been studied. Structure of new polyfunctional silanes has been confirmed by IR and NMR spectroscopy. [ABSTRACT FROM AUTHOR]

One-pot synthesis in organic chemistry is deeply rooted in people's minds due to its huge improvement in efficiency compared with conventional stepwise synthesis. Nowadays, such a concept has also been shifted to polymer chemistry by one-pot introducing compatible or orthogonal organic reactions with polymerizations for facilely synthesizing or modifying polymers. This review systematically summarizes recent developments in the one-pot combination of enzymatic reactions with controlled radical polymerization to prepare functional polymers. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Using air as the oxygen source, 4-carbonyl-2-perfluoroalkylquinolines were prepared in good to excellent yields, from readily available 2-alkynylanilines and methyl perfluoroalk-2-ynoates through a CuII-promoted sequential process that omits the isolation of the enamine intermediates. The reaction tolerates several useful functionalities including ether, ester and chloro substituents. [ABSTRACT FROM AUTHOR]

The direct functionalization of unactivated sp3 C-H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts, the establishment of general and mild strategies for the engagement of sp3 C-H bonds in C-C bond forming reactions has proved difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene and methine carbons in a catalytic manner is a priority. Although protocols for direct oxidation and amination of allylic C-H bonds (that is, C-H bonds where an adjacent carbon is involved in a C = C bond) have become widely established, the engagement of allylic substrates in C-C bond forming reactions has thus far required the use of pre-functionalized coupling partners. In particular, the direct arylation of non-functionalized allylic systems would enable access to a series of known pharmacophores (molecular features responsible for a drug's action), though a general solution to this long-standing challenge remains elusive. Here we report the use of both photoredox and organic catalysis to accomplish a mild, broadly effective direct allylic C-H arylation. This C-C bond forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants, and has been used in the direct arylation of benzylic C-H bonds. [ABSTRACT FROM AUTHOR]

Substituted 3-alkyloxycyclobutanones are highly valuable intermediates in organic synthesis, which demonstrate interesting and rich reactivity in different types of reactions due to the strain energy. Under Lewis acid catalysis, 3-alkyloxycyclobutanones can form zwitterionic intermediates and participate in a series of cycloaddition reactions as three- or four-carbon synthons. This Focus Review will mainly discuss formal [4+2], [3+2], and [3+3] annulations as well as other types of transformations with 3-alkyloxycyclobutanones. [ABSTRACT FROM AUTHOR]

The reaction mechanisms and chemoselectivity on the intramolecular allylic C-H amination versus alkene aziridination of 4-pentenylsulfamate promoted by four elaborately selected dirhodium paddlewheel complexes are investigated by a DFT approach. A predominant singlet concerted, highly asynchronous pathway and an alternative triplet stepwise pathway are obtained in either C-H amination or alkene aziridination reactions when mediated by weak electron-donating catalysts. A singlet stepwise C-H amination pathway is obtained under strongly donating catalysts. The rate-determining step in the C-H amination is the H-abstraction process. The subsequent diradical-rebound C-N formation in the triplet pathway or the combination of the allylic carbocation and the negative changed N center in the singlet pathway require an identical energy barrier. A mixed singlet-triplet pathway is preferred in either the C-H insertion or alkene aziridination in the Rh2(NCH3CHO)4 entry that the triplet pathway is initially favorable in the rate-determining steps, and the resultant triplet intermediates would convert to a singlet reaction coordinate. The nature of C-H amination or alkene aziridination is estimated to be a stepwise process. The theoretical observations presented in the paper are consistent with the experimental results and, more importantly, provide a thorough understanding of the nature of the reaction mechanisms and the minimum-energy crossing points. [ABSTRACT FROM AUTHOR]

By coupling surface-enhanced Raman spectroscopy (SERS) with thin layer chromatography (TLC), a facile and powerful method was developed for on-site monitoring the process of chemical reactions. Samples were preseparated on a TLC plate following a common TLC procedure, and then determined by SERS after fabricating a large-area, uniform SERS substrate on the TLC plate by spraying gold nanoparticles (AuNPs). Reproducible and strong SERS signals were obtained with substrates prepared by spraying 42-nm AuNPs at a density of 5.54 × 1010 N/cm² on the TLC plate. The capacity of this TLC-SERS method was evaluated by monitoring a typical Suzuki coupling reaction of phenylboronic acid and 2-bromopyridine as a model. Results showed that this proposed method is able to identify reaction product that is invisible to the naked eye, and distinguish the reactant 2-bromopyridine and product 2-phenylpyridine, which showed almost the same retention factors (Rf). Under the optimized conditions, the peak area of the characteristic Raman band (755 cm-1) of the product 2-phenylpyridine showed a good linear correlation with concentration in the range of 2-200 mg/L (R² = 0.9741), the estimated detection limit (1 mg/L 2-phenylpyridine) is much lower than the concentration of the chemicals in the common organic synthesis reaction system, and the product yield determined by the proposed TLC-SERS method agreed very well with that by UPLC-MS/MS. In addition, a new byproduct in the reaction system was found and identified through continuous Raman detection from the point of sample to the solvent front. This facile TLC-SERS method is quick, easy to handle, low-cost, sensitive, and can be exploited in on-site monitoring the processes of chemical reactions, as well as environmental and biological processes. [ABSTRACT FROM AUTHOR]

A tandem reaction of benzyne with functionalized benzylidenephthalan for the synthesis of a variety of phenanthro[10,1-bc]furans has been achieved for the first time in moderate to good yields. The reaction mechanism involves a Diels-Alder reaction and an intermolecular nucleophilic addition reaction as the key steps. [ABSTRACT FROM AUTHOR]

Treatment of oxazolidinediones with TiCl4 in CH2Cl2 resulted in conversion to isoindoloisoquinolinones via intramolecular Friedel-Crafts reaction with extrusion of CO2 in the transformation. The alkaloid nuevamine has been synthesized under these conditions in a regiospecific manner. [ABSTRACT FROM AUTHOR]

Two new protocols for the efficient synthesis of 2,2,2-trichloromethylcarbinols, starting from aromatic aldehydes, have been developed. A combination of sodium trichloroacetate in the presence of malonic acid proved efficient for the transformation of electron deficient aldehydes using DMSO as solvent. Electron-rich aldehydes did, however, not require the addition of malonic acid, affording the desired 2,2,2-trichloromethylcarbinols without a trace of the competing Cannizzaro reaction. Finally, the reaction of sodium trichloroacetate in THF with a mixture of aldehyde and malonic acid dissolved in DMSO allowed the protocol to be performed in continuous flow. By performing this decarboxylative reaction in continuous flow, scale-up of the reaction could be achieved with a simple and safe setup. In this flow setup, four electron-deficent aldehydes were successfully transformed into their 2,2,2-trichloromethylcarbinol derivatives on a 100 mmol scale. [ABSTRACT FROM AUTHOR]

New compounds involving the biologically important 1,4-benzodiazepine skeleton were conveniently constructed from 2-(arylamino)benzamides through PhI(OAc)2-mediated oxidative C-N bond formation. The attractive features of this new synthetic strategy include mild reaction conditions, the heavy-metal-free characteristic of the oxidative coupling process, and the flexibility to tolerate a broad scope of substrates. [ABSTRACT FROM AUTHOR]

Three endo bicyclooctadienol dimers corresponding to kingianins A and H, D, and F and J were obtained by the intermolecular radical cation Diels-Alder (RCDA) reaction. Each isomer was cleanly isolated without the aid of preparative HPLC. Kingianins D, F, H, and J were prepared by way of these intermediates from commercially available materials in 10, 13, 9, and 17 steps, respectively. Kingianin A has already been prepared from one of these compounds. Completion of the synthesis of kingianin H relied on Manchand's one-step, three-carbon homologation. [ABSTRACT FROM AUTHOR]

A short and efficient synthesis of the pentacyclic core of the indole alkaloid tronocarpine is described. The synthetic pathway involves several easily accomplished steps, including a radical oxidative aromatic substitution reaction on the N- tert-butoxycarbonyl-protected tryptamine and a xanthate, a 1,4-1,2-nucleophilic addition between a 2,3-disubstituted indole and an α,β-unsaturated aldehyde, and a Ti-mediated Dieckmann condensation. This report represents a significant advance in the quest for the first total synthesis of tronocarpine. [ABSTRACT FROM AUTHOR]

Short oligodeoxyribonucleotides have been assembled from appropriately protected nucleoside 3′-(benzotriazol-1-yl 2-chlorophenyl phosphate) derivatives on hundred-milligram scales on a soluble tetrakis- O-(4-azidomethylphenyl)pentaerythritol support bearing four 3′- O-(4-pentynoyl)thymidines. Small-molecule reagents and waste were removed by two precipitations of the support-bound growing oligonucleotides with methanol, the first after removal of the 5′-protecting group and the second after coupling. The building blocks were obtained by one-step phosphorylation of commercially available protected nucleosides with bis(benzotriazol-1-yl) 2-chlorophenyl phosphate. Removal of the phosphate protecting groups from the completed chain with ( E)-2-nitrobenzaldoxime followed by conventional ammonolysis allowed precipitation of the oligonucleotide as the sodium salt with ethanol. [ABSTRACT FROM AUTHOR]

A practical and scalable route was developed for the total synthesis of gossypol to allow for the construction of dozens of gossypol derivatives. tBuO2Ac was found to be a highly efficient oxidant for the polymerization of hemigossypol through a biosynthetic process under nonenzymatic conditions to give gossypol. Hemigossypol was synthesized on a gram scale by starting from commercially available carvacrol and dimethyl succinate and using a Stobbe condensation, an electrophilic cyclization, and the Michael addition of ortho-quinone methide as key steps. [ABSTRACT FROM AUTHOR]

The desulfonylation of β-arylketosulfones has been achieved in good to excellent yields by using 3-W blue LEDs light, 1 mol-% organic dye eosin Y bis(tetrabutylammonium salt) as photocatalyst, and diisopropylethylamine as reducing agent. Mechanistic studies demonstrate that oxidative quenching of the excited eosin Y by β-arylketosulfones plays a crucial role in the present photoredox catalytic cycle. [ABSTRACT FROM AUTHOR]

From methyl to nitrile: A mild ammoxidation method, which directly converts methyl arenes into aromatic nitriles, has been developed by using Pd(OAc)2 and N‐hydroxyphthalimide (NHPI) as the catalysts, and tert‐butyl nitrite as the nitrogen source and oxidant. [ABSTRACT FROM AUTHOR]

Cp*Rh(III)-catalyzed intermolecular C-C couplings between activated α-diazocarbonyl compounds and arenes bearing a range of azacyclic directing groups have been achieved. This catalytic alkylation reaction operates under mild conditions with good functional group tolerance. [ABSTRACT FROM AUTHOR]

An iron-catalyzed reaction of 2-arylpyridine C-H bond with 2-bromoacetophenone is achieved, providing pyrido[2,1-a]- isoindoles in moderate to good yields. The regioselectivity stems from the domination of hindrance on the regioselective ortho-func- tionalization of 2-arylpyridines C-H bond. [ABSTRACT FROM AUTHOR]

The copper(I) chloride catalyzed reaction of azides with alkynes in water at room temperature was promoted by the addition of a catalytic amount of 2-ethynylpyridine, affording the corresponding 1,4-disubstituted 1,2,3-triazoles in good yields after a specific reaction time. The catalytic system could be successfully applied to electron-rich, electron-poor, and sterically crowded substrates. A study of the additive effect of pyridine derivatives revealed that alkynyl and 2-pyridyl groups were essential for activating the copper catalyst. [ABSTRACT FROM AUTHOR]

Arylated flavones were prepared by Suzuki-Miyaura reactions of 6-bromo-3-(trifluoro-sulfonyloxy)flavone. The reactions proceeded with very good chemoselectivity in favor of position 3. [ABSTRACT FROM AUTHOR]

The evolution of organocatalysis led to various valuable approaches, such as multicomponent as well as domino and tandem reactions. Recently, organomulticatalysis, i.e., the modular combination of distinct organocatalysts enabling consecutive reactions to be performed in one pot, has become a powerful tool in organic synthesis. It allows the construction of complex molecules from simple and readily available starting materials, thereby maximizing reaction efficiency and sustainability. A logical extension of conventional multicatalysis is a multicatalyst, i.e., a catalyst backbone equipped with independent, orthogonally reactive catalytic moieties. Herein we highlight the impressive advantages of asymmetric organomulticatalysis, examine its development, and present detailed reactions based on the catalyst classes employed, ranging from the very beginnings to the latest multicatalyst systems. [ABSTRACT FROM AUTHOR]

A stereoselective synthesis of the hemlock alkaloid (R)- coniine and a formal synthesis of the indolizidine alkaloid (S)-dconiceine were achieved by means of a highly diastereoselective Barbier-type indium-mediated allylation strategy involving (S)-(Ntert- butanesulfinyl)imines. [ABSTRACT FROM AUTHOR]

A systematic study of the reaction conditions for the preparation of pure aryl-H-phosphinate esters, originally developed by Sander and optimized by Petneházy, is reported. The influence of the reaction concentration has been investigated for the formation of phosphonite intermediates via direct addition of triethyl phosphite to the appropriate Grignard reagent. Subsequent hydrolysis of the phosphonites under acidic conditions gives various aryl-Hphosphinates in high yields and purities. [ABSTRACT FROM AUTHOR]

A racemic cyclopentannulated pyrrolidine derivative was synthesized utilizing ruthenium oxidation and borane reduction as the key steps. Ruthenium oxidation reaction of the 1,2-dibromoalkene moiety in an N-Boc-protected tetrabromonorbornyl derivative afforded a tricyclic α-hydroxy ketone, which on alkaline hydrogen peroxide cleavage furnished a bicyclic lactam in excellent yield. Borane reduction of the N-Boc-protected bicyclic lactam gave an unexpected product as a single diastereomer resulting from the reduction of not only the lactam and ester moieties but also the ketal to the corresponding methyl ether. A plausible mechanism involving an oxocarbenium ion is discussed. [ABSTRACT FROM AUTHOR]

The nucleophile-induced rearrangement of cyclic Nalkoxy- N-(silyloxy)enamines was investigated. As a result, a new strategy for the synthesis of β-pyranone and β-furanone derivatives from nitro compounds is suggested. [ABSTRACT FROM AUTHOR]

A general method has been developed for the selective synthesis of 3-iodoquinolin-2-ones and spiro[4.5]trienes via intramolecular iodocyclization of N-(ortho-substituted aryl)-3-phenylpropiolamides using iodine/cerium(IV) ammonium nitrate reagent under mild reaction conditions. The electronic effect of ortho-substituents (electron-rich and electron-deficient group) triggers the two different reaction pathways resulting to iodocyclized quinolin-2-one and ipso-iodocyclized spiro-type compounds. [ABSTRACT FROM AUTHOR]

Imidazo[1,2-a]pyridine-3-carboxylates can be prepared directly from 2-aminopyridines and β-keto esters by using bis(acetyloxy)(phenyl)-&#x03BB³;-iodane as an oxidant and boron trifluoride etherate as a catalyst. The amount of catalyst plays a key role in determining the course of the reaction. Whereas the use of 0.2 equivalents of catalyst ensures the generation of imidazo[1,2-a]pyridines, raising the amount of catalyst to 1.0 equivalents results in exclusive α-acetoxylation of the β-keto esters. 2-Aminopyridines can also react with 1,3-diones to afford 3-acylimidazo[1,2-a]pyridines. [ABSTRACT FROM AUTHOR]

α-Thiocyanate ketone-based three-component reactions have been established for the stereoselective synthesis of functionalized electron-deficient trans-cyclopropanes. The multicomponent reactions were conducted by reacting readily available and inexpensive starting materials under microwave irradiation. The procedures are very facile, highly stereoselective, and avoids the use of ylides. [ABSTRACT FROM AUTHOR]

Cerium(IV) ammonium nitrate mediated oxidative addition of 1,3-dicarbonyl compounds to terminal acetylenes to yield multisubstituted furan derivatives is reported here. The simplicity of the reaction and the ease of execution are particularly noteworthy. [ABSTRACT FROM AUTHOR]

A simple and efficient route to N6-acetyl-2′,3′,5′-tri-Oacetyladenosine (1) was developed based on selective N-deacetylation of pentaacetylated adenosine 2 with methanol at room temperature in the presence of imidazole. Preparative synthesis of 1 was elaborated utilizing a crude mixture of 2 and 1 which is produced by reaction of adenosine with acetic anhydride in pyridine at elevated temperatures. The total yield of 1 was 80-85% starting with adenosine. It was shown that 1 is a convenient substrate for selective N6- alkylations. The study revealed the same regioselectivity in basepromoted reactions of 1 with activated alkyl halides and Mitsunobu reactions of 1 with alcohols. A series of N6-alkyladenosines 5a-f were prepared. Cytokinins 6b,d,e were prepared by enzymatic transformation of parent nucleoside derivatives 5b,d,e using a combination of nucleoside phosphorylase and alkaline phosphatase. [ABSTRACT FROM AUTHOR]

Indium(III) chloride catalyzes the ring opening of chalcone epoxides followed by intramolecular Friedel-Crafts alkylation under mild conditions at room temperature to afford highly functionalized 3-aryl-2-hydroxy-2,3-dihydro-1H-inden-1-ones in excellent yields (81-95%). [ABSTRACT FROM AUTHOR]

A convenient method for the efficient and regioselective monofluorination of allyl silanes to afford 1-fluoro-3-silyl-2-ols in 43-62% yields via fluorohydroxylation, using Selectfluor as the eletrophilic fluorination reagent has been developed. The regioselectivity can be rationalized by considering the stabilization of the β-carbocation intermediate by the silyl group. [ABSTRACT FROM AUTHOR]

The new chiral thiophene 3 was prepared from (+)-nopinone via a de novo construction of the thiophene nucleus. From compound 3 four new S,S- and N,S-ligands, namely the C1-symmetric 2-(thiophen-2-yl)pyridine 7 and the C2-symmetric 2,2′- bithiophene 5, 2,6-di(thiophen-2-yl)pyridine 8, and 2,6- di(thiophen-2-yl)thiophene 9 were synthesized. [ABSTRACT FROM AUTHOR]

The inexpensive starting material, 1,1-dichloroethylene, was used as a substitute for 1,2-dichloroethylene to synthesize unsaturated thiacrown ethers through the reaction of 1,1-dichloroethylene with sodium sulfide in the presence of a 15-crown-5 catalyst. Besides the compounds containing cis-carbon-carbon double bonds, two unsaturated thiacrown ethers each containing one transcarbon- carbon double bond were also isolated. [ABSTRACT FROM AUTHOR]

Exploratory oxidative cyclization studies on cyclopentanelated and cyclohexenelated oroidin derivatives utilized Pummerer chemistry to generate pentacyclic structures related to the palau'amine family of sponge metabolites. Stereochemical issues were paramount, and appropriate choice of annelated ring size led to formation of the pentacyclic framework with complete diastereoselectivity for all of the core bonds. [ABSTRACT FROM AUTHOR]

The title compound was synthesized by multicomponent condensation of 3-amino-1,2,4-triazole, acetone and 5-bromo-2-hydroxy-3-methoxybenzaldehyde. The structure was established by ³H-NMR, 13C-NMR, IR spectroscopy and LC-MS. [ABSTRACT FROM AUTHOR]

A new synthetic strategy for C–C bond formation has been developed via a free radical cascade process under metal-free conditions. Activation of inert C(sp3)–H/elimination of SO2/C–C bond formation were achieved in sequence in this system. [ABSTRACT FROM AUTHOR]

The synthesis of silaheterocycles through the first examples of an intramolecular silene Diels–Alder reaction is described. [ABSTRACT FROM AUTHOR]

The versatile tri-tert-butylphosphonium tetrafluoroborate ligand is prepared in a convenient, simple, and high-yielding procedure without the isolation of sensitive intermediates. [ABSTRACT FROM AUTHOR]

The article focuses on a chemical study done to synthesize adamantane-containing nitroso- and aminopyrazoles. It discusses the chemical reactions which were performed during the study. It mentions that the mass spectra were acquired on a Finnigan Trace DCQ mass spectrometer. It further states that the TermoFinnigan Flash1112 NCH analyzer was used to determine the elemental compositions.

A report is presented on stereospecific synthesis of E,E-bis(2-chlorovinyl) selenide (II) based on the reaction of selenium dichloride and tetrachloride with acetylene. The authors note that selenide II is important as an intermediate for organic synthesis. The method of performing the reaction is explained, along with the formula leading to selenide II.

A report is presented on the carboxyalkylation of ethylene diamine with β-chloropropionic acid. It describes how reactive ethylene diamine-N,N'-dipropionic acid II is the initial reagent which is incorporated into organic compounds to obtain other reagents. It examines the benefits and drawbacks of other methods of synthesis and describes reaction procedures.

The article discusses the reactions of aminoacetaldehyde diethylacetal and dimethylaminoacetaldehyde diethylacetal with 2-methylresorcinol for calixarenes synthesis. It mentions that the synthetic results of the reaction of the compounds depend on the conditions of the reaction. It provides a comprehensive discussion on the preparation and synthesis of several compounds. It notes that UR-20 spectrometer was used to show the infrared spectra of the compounds studied for the research.