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The article discusses the synthesis and catalytic properties of Donor-Acceptor Stenhouse Adducts (DASAs). DASAs are triene substances that can be prepared using specific reagents and conditions. The study explores the use of Lewis acids as catalysts for transforming DASAs into their ring isomers, and suggests potential applications as photosensors and Lewis acid sensors. The document provides detailed experimental procedures and results for the synthesis and characterization of various compounds, as well as a general procedure for the one-pot cyclization of DASAs. [Extracted from the article]

The elaboration of azo dyes using a variety of transition-metal-catalysed reactions (Stille, Heck, Ullmann, and Suzuki couplings) is reported. This methodology has been applied to the synthesis of functionalised coumarin azo dye conjugates, substrates which may find potential application in the development of new sensors. [ABSTRACT FROM AUTHOR]

An interview with Frank Glorius, a professor at the University of Münster who won the 2015 Best Paper Award of the journal "SYNLETT," is presented. Topics include his award-winning paper on the asymmetric hydrogenation of 2-pyridones; research activity of Glorius and his team which focuses on fields such as catalysis, photocatalysis, and carbon-hydrogen (C-H) activation chemistry; and challenges and prospects of organic synthesis.

An interview with Prof. Erwan Poupon and Dr. Laurent Evanno, professors of pharmacognosy at Paris-Sud University, is presented. The questions involves on the strategic approach to dimerize an aplysinopsin-type starting material through liquid chromatography-mass spectrometry, their several drug-design projects from natural product scaffolds, and the prospect of organic synthesis specifically on natural product chemistry and biomimetic approaches.

In this paper, an iron-catalyzed deboronation/cyanoalkylation of vinyl boronic acids for the preparation of distal cyanoalkyl alkenes with vinyl boronic acids as radical acceptor and activator is reported. In this reaction, various cyclobutanone oximes and substituted vinyl boronic acids can be transformed into the corresponding cyanoalkylated alkenes in moderate to good yields under these conditions. Mechanistic studies indicated that a single-electron transfer process may be involved in this transformation. [ABSTRACT FROM AUTHOR]

Olefin metathesis, which is well established in the petrochemical industry, is also emerging as a green technology in the manufacture of pharmaceutical and specialty chemicals. Arylbenzofurans are of interest for potential medicinal applications. In this paper we report on the synthesis of various 2-aryl- and 3-arylbenzo[ b ]furans with natural substitution patterns from readily available starting materials in a strategy that applies ring-closing metathesis with the Grubbs second generation catalyst as key step. [ABSTRACT FROM AUTHOR]

This paper outlines a novel strategy for the preparation of seven-membered-ring lactams from simple nitroarenes. The approach is based on a photochemical dearomative ring expansion starting with the conversion of the nitro group into a singlet nitrene. This process is mediated by blue light, occurs at room temperature and overall enables the insertion of the nitro N -atom into the benzenoid framework. This step transforms the aromatic starting material into a seven-membered ring azepine that, following hydrogenation and hydrolysis, is converted into the desired caprolactams in just three steps. [ABSTRACT FROM AUTHOR]

A protocol for the reductive alkylation of unprotected aminocyclitols with supported reagents and scavengers is described. The method is operatively simple and provides the corresponding secondary amines in high yields and purities. [ABSTRACT FROM AUTHOR]

This article explores the use of thioether-containing ligands in catalysis applications. Thioether ligands, which contain a sulfur atom, have traditionally been less considered due to their lower donor and acceptor character compared to phosphorus ligands. However, ligands with a low degree of oxidation and a combination of sulfur with another heteroatom have shown promise in generating interesting catalysts. The article provides examples of enantioselective and non-enantioselective reactions using thioether ligands and discusses the advantages of combining sulfur with another heteroatom. The paper is organized based on the type of heteroatom that accompanies the thioether function, such as phosphorus and nitrogen. Various catalytic systems involving thioether ligands for different organic transformations are discussed, including dihydroboration, cyclopropanation, silyl-hydrogen insertion, C-H functionalization, and C-H alkenylation. The ligands play a crucial role in enhancing the activity and selectivity of the catalysts, and they have been successfully applied to a wide range of substrates. Mechanistic studies have provided insights into the reaction pathways and the role of the ligands in facilitating the transformations. The article highlights the potential of thioether-functionalized ligands in metal-catalyzed reactions and suggests a promising future for sulfur in catalysis. [Extracted from the article]

This article discusses the application of the Heck reaction for the synthesis of C-glycosyl phenolic compounds. The authors successfully synthesized C-glycosylated 2-styrylchromones and xanthones with high stereoselectivity. The article also includes detailed experimental procedures and characterization data for the synthesized compounds. The given text appears to be a scientific article or research paper that includes data related to chemical compounds. The text provides information about the chemical structure and properties of different compounds, including their nuclear magnetic resonance (NMR) spectra, mass spectrometry data, and physical characteristics. The compounds mentioned in the text are described in terms of their chemical composition, yield, and various spectroscopic data. [Extracted from the article]

In this paper, compound B 62 b is used as a lead compound for structural modification in order to improve the antibacterial and anti-biofilm potency. Compared with compounds B 3b b - B h b (with different R SP 3 sp substituents), compound B 3a b , with R SP 3 sp = 2-OH, demonstrated significant inhibitory activity on the biofilm formation of the three tested bacterial strains. Interestingly, compound B 3i b with limited anti-biofilm activity against I E. faecalis i FB1 showed a significant inhibitory effect on I Staphylococcus i ( I S. epidermidis i SE1457 and MSSA SA113) biofilm formation. Keywords: dihydropyrrolidone; 1,3,4-thiadiazole; derivatization; antibacterial; anti-biofilm EN dihydropyrrolidone 1,3,4-thiadiazole derivatization antibacterial anti-biofilm 2099 2108 10 06/16/23 20230704 NES 230704 Antibiotic-resistant bacteria have become a major concern for public health professionals. [Extracted from the article]

Bempedoic acid is a small-molecule inhibitor of adenosine triphosphate-citrate lyase (ACL) that is effective in the treatment of hypercholesterolemia and hypertension. In this paper, a new, six-step synthesis of bempedoic acid with 42% overall yield is reported. Ketone formation by electrochemical decarboxylation of dialkylated malonic acid is introduced as the key step of this process. This method uses mild conditions and its high efficiency makes it potentially suitable for industrial production. [ABSTRACT FROM AUTHOR]

In this paper, the synthesis of the carbon skeleton of cotylenin A aglycone is described. The key reactions, including an intramolecular aldol reaction, an aldol coupling reaction, and a ring-closing meta-thesis, allow for the effective and stereoselective access to the carbon skeleton of cotylenin A aglycone. The stereochemistry was confirmed by single-crystal X-ray crystallographic analyses of related compounds. [ABSTRACT FROM AUTHOR]

Covalent triazine frameworks (CTFs) based on polydentate ligands are highly promising supports to anchor catalytic metal complexes. The modular nature of CTFs allows to tailor the composition, structure, and function to its specific application. Access to a broad range of chelating building blocks is therefore essential. In this respect, we extended the current available set of CTF building blocks with new nitrile-functionalized N-heterocyclic ligands. This paper presents the synthesis of the six ligands which vary in the extent of the aromatic system and the denticity. The new building blocks may help in a rational design of enhanced support materials in catalysis. [ABSTRACT FROM AUTHOR]

In this paper, a unique process for the production of methyl anthranilate (MA) was investigated. The factors of the phthalimide/sodium hypochlorite/methanol molar ratio, reaction temperature, hydrolysis temperature, and water consumption on the yield and purity of MA were analyzed. Response surface methodology (RSM) was used to optimize conditions for the semi-batch synthesis process of MA. The best synthetic conditions for the formation of MA were reaction temperature 0.5 °C, hydrolysis temperature 70 °C and n (phthalimide)/ n (sodium hypochlorite)/ n (methanol) = 1:2.03:5.87, and water consumption m (H2 O)/ m (phthalimide) = 7.16:1. The yield of MA could reach 90% under the optimal conditions, which is more than 10% higher than that of the previous semi-batch process. Furthermore, the reaction mechanism was investigated by infrared spectroscopy analysis, and the mechanism of ester group formation and the structure of intermediate products are proposed. The byproduct of the reaction was studied by GC-MS analysis, a byproduct called 2-cyanobenzoic acid has been discovered. Therefore, an unprecedented reaction mechanism of the whole synthesis process is proposed. [ABSTRACT FROM AUTHOR]

Chiral sulfoxide is considered to be an ideal candidate ligand for transition-metal-catalyzed asymmetric reactions due to its ease of synthesis, stability, and exceptional S -stereological orientation control. This paper reviews the different types of asymmetrical reactions with chiral sulfoxide ligands in recent years, as well as a discussion of efficient methods for the preparation of some enantiomerically pure sulfoxides. 1 Introduction 2 Chiral Sulfoxides as Ligands in Metal-Catalyzed Asymmetric Catalysis 3 Synthesis of Chiral Sulfoxides 4 Conclusions [ABSTRACT FROM AUTHOR]

The most recent advances in the construction of oxygen heterocycles by the directing-group-assisted transition-metal-catalyzed direct oxidative annulation of arenes with diverse alkynes are summarized in this review. More than 140 recent research papers and many closely related reviews are referenced in this paper. Nine different oxygen heterocycles frameworks are discussed. Several traditional transition-metal catalysts as well as some classical non-noble metals are utilized to promote the annulation. Three plausible controlling models are disclosed to clarify the excellent regioselectivity outcomes achieved in case of unsymmetrical alkyne substrates. 1 Introduction 2 Coumarins 3 I socoumarins and Their Analogues 4 2-Pyrones and Their Analogues 5 Chromones and Chroman-4-ones 6 Chromenes and Isochromenes 7 Fused Polycyclic Oxygen Heteroaromatics 8 Benzofurans, Dihydrobenzofurans, and Furans 9 Phthalides and Benzofuranones 10 Benzoxepines 11 Conclusion [ABSTRACT FROM AUTHOR]

In this paper, we report the Pd(II)-catalyzed, picolinamide DG-aided sp2 γ-C–H functionalization and expansion of the library of enantiopure α-methylbenzylamine and phenylglycinol scaffolds. We have shown the synthesis of a wide range of racemic and enantiopure ortho -C–H arylated, alkylated, brominated, and iodinated α-methylbenzylamine and phenylglycinol scaffolds. Various racemic and R and S (chiral) sp2 γ-C–H functionalized α-methylbenzylamine and phenylglycinol scaffolds were synthesized with good enantiopurities. Racemic and enantiopure α-methylbenzylamine and phenylglycinol derivatives are important building blocks in organic synthesis and medicinal chemistry. Accordingly, this work contributes to the expansion of the libraries of α-methylbenzylamine and phenylglycinol motifs and substrate scope development through the Pd(II)-catalyzed bidentate directing group picolinamide-aided site-selective C–H activation and functionalization method. [ABSTRACT FROM AUTHOR]

This paper describes a continuous multi-step synthesis in supercritical CO2. A continuous flow synthesis of 2-substituted 1,4-benzoquinones is reported, and details of the high-pressure reactors are given. This proceeds via the telescoped dearomatisation of p -substituted phenols using singlet oxygen in supercritical CO2 and an acid-mediated C–C migration. The process has a short residence time of 30 minutes, with overall yields and projected productivities of up to 83% and 9 g/day, respectively. This methodology enables a safe and efficient synthesis of 2-substituted 1,4-benzoquinones from photo-generated singlet oxygen, and cheap and readily available p -substituted phenols. The procedure has high atom efficiency, low photocatalyst loading, and substitutes potentially hazardous and corrosive reagents and solvents for molecular oxygen, CO2 , and the less hazardous solid-supported acid Amberlyst-15. [ABSTRACT FROM AUTHOR]

Drug development based on phenolic natural products as drug candidates against various diseases has gained much attention in recent years. However, most of those molecules lack therapeutic efficacy in clinical trials, usually due to poor bioavailability. Therefore, a prodrug approach was adopted to address the bioavailability problem of phenolic drugs. This paper describes a mild and convenient method for late-stage ProTide-type prodrug synthesis of phenolic pharmaceuticals, which gives various phosphoramidate prodrugs from unprotected phenolic natural products and drugs in high yield. More importantly, this reaction is amenable for the selective phosphorylation of the phenolic hydroxyl group in the presence of otherwise problematic nucleophilic functional groups like amines and alcohols. We also observed that the chemical release rate of the phenol can be substantially tuned by changing the amino acid residue on the phosphoramidate moiety. [ABSTRACT FROM AUTHOR]

The present study describes the one-pot palladium-catalyzed cyanation of commercially available aryldiazonium tetrafluoroborate derivatives with 2-(piperidin-1-yl)acetonitrile (an organic cyano reagent) under mild conditions. This process utilizes a Pd/(Me3 Si)2 system and is applied to a wide scope of aromatic diazonium substrates to give the corresponding nitrile-containing products in moderate to high yields (59–92%). This methodology is employed for the preparation of etravirine, a drug used for the treatment of HIV, and for transformations of 1 H -indole-2-carbonitrile into compounds that are used as a NMDA receptor antagonists and that have high potential against mutant HIV strains. The mechanism proposed for this Pd-catalyzed cyanation involves cyanide ions, as confirmed using indicator paper. [ABSTRACT FROM AUTHOR]

In this paper, we report the first total synthesis of goniothaline A and B, which are rare natural pyridocoumarins isolated from Goniothalamus australis. The key feature of the synthesis of goniothaline A is high-yielding silver-catalyzed cycloisomerization to afford the pyridine moiety. In addition, goniothaline B, a natural 8-hydroxyquinoline derivative, is readily synthesized by the regioselective demethylation of goniothaline A. [ABSTRACT FROM AUTHOR]

Catalyst-free dehalogenation of a-haloketones under visible light irradiation is studied. The reactions were carried out in common organic solvent. The outcomes of dechlorination are excellent in yields up to 92%, and it is also applicable to bromides, which give even higher yields. The reaction is tolerable to a broad spectrum of substrates, especially to aromatic ketones, including various aryl and hetaryl groups. There are two examples of aliphatic ketones presented in the paper, although their reactivities are not as high as that of the aromatic ketones. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed nitrene transfer is a convenient method to introduce nitrogen into simple substrates through either alkene aziridination or C-H bond amination. Silver complexes have an unusual capability to accommodate a broad range of N-donor ligands and coordination geometries in catalysts competent for nitrene transfer. This behavior has resulted in the ability to achieve tunable chemoselectivity between aziridination and C-H bond amidation, as well as tunable site-selective functionalization between two different C-H bonds. In this paper, efforts to engage the diversity of silver and rhodium catalysts to accomplish selective and tunable aziridination of mixtures of alkenes are discussed. It was found that the selectivity of dinuclear Rh catalysts is dictated largely by steric effects, while the identity of the ligand on silver can be tuned to influence whether the steric or electronic features in the competing alkenes is the primary factor controlling which precursor is preferentially aziridinated. [ABSTRACT FROM AUTHOR]

Biarylboronic esters are generally prepared by directed ortho-metalation or by Miyaura borylation and hence rely on the presence of a directing group or pre-functionalization. In this paper, the preparation of biarylboronic esters by direct C-H borylation of biaryl substrates is reported. Sterically governed regioselectivities were observed in the borylation of appropriately substituted biaryls by using [Ir(OMe)(COD)]2 precatalyst and di-tert-butylbipyridyl ligand. The resulting biarylboronic esters were isolated in 38-98% yields. The synthesized biarylboronic esters were further successfully employed in C-O, C-Br, and C-C coupling reactions. [ABSTRACT FROM AUTHOR]

In this paper, we report the first total synthesis of (+)-coprophilin, an anticoccidial agent, by constructing the chiral linear precursor via a Mukaiyama--Evans aldol reaction and a stereoselective intramolecular Diels--Alder reaction. The proposed method can be used to provide large amounts of (+)-coprophilin, which exhibits a 3,4,5,6,7-pentasubstituted Δ1,2-octalin core structure. [ABSTRACT FROM AUTHOR]

C–H bonds are ubiquitous and abundant in organic molecules. If such C–H bonds can be converted into the desired functional groups in a site-, chemo-, diastereo-, and enantio-selective manner, the functionalization of C–H bonds would be an efficient tool for step-, atom- and redox-economic organic synthesis. C–H oxidation, as a typical C–H functionalization, affords hydroxy and carbonyl groups, which are key functional groups in organic synthesis and biological chemistry, directly. Recently, significant developments have been made using non-heme-type transition-metal catalysts. Oxygen functional groups can be introduced to not only simple hydrocarbons but also complex natural products. In this paper, recent developments over the last fourteen years in non-heme-type complex-catalyzed C–H oxidations are reviewed. 1 Introduction 2 Regio- and Chemo-Selective C–H Oxidations 2.1 Tertiary Site-Selective C–H Oxidations 2.2 Secondary Site-Selective C–H Oxidations 2.3 C–H Oxidations of N-Containing Molecules 2.4 C–H Oxidations of Carboxylic Acids 2.5 Chemo- and Site-Selective Methylenic C–H Hydroxylations 3 Enantioselective C–H Oxidations 3.1 Desymmetrizations through C–H Oxidations 3.2 Enantiotopic Methylenic C–H Oxygenations 4 Conclusion [ABSTRACT FROM AUTHOR]

In recent years, advancements in photocatalysis have allowed for a plethora of chemical transformations under milder conditions. Many of these photochemical reactions utilize hydrogen atom transfer processes to obtain desired products. Hydrogen atom transfer processes can follow one of two unique pathways: the first, a direct path and the second, an indirect path. In this paper, we highlight the ability of eosin Y to act as a direct hydrogen atom transfer catalyst from both synthetic and computational chemistry perspectives. [ABSTRACT FROM AUTHOR]

Nowadays, the development of new approaches which smartly bypass the use of harsh reaction conditions and hazardous chemicals covers a pivotal role. In this research paper the synthesis, characterization, and application of novel libraries of triazine bis-quaternary ammonium salts, employed as coupling agents to produce amides is reported. Full characterization of the novel compounds by1 H and13 C NMR, FT-IR spectroscopy, ESI-HRMS, and elemental analysis is provided. Furthermore, a comparison in terms of activity of the preformed triazine compounds versus in situ formulations has been evaluated for the formation of amides in the presence of phenylethylamine and different aliphatic or aromatic acids. A possible correlation between the chemical structure of the triazine and their reactivity for the formation of the triazine bis-quaternary ammonium salts is also reported. Moreover, best performing condensation agents have been further tested for the cross-linking of collagen powder as possible wet white tanning systems, for sustainable and environmentally friendly leather tanning. [ABSTRACT FROM AUTHOR]

Indoles are one of the most valuable nucleophiles in Michael additions catalyzed by a proper Lewis acid. In this paper, we found that a cationic iron salt is effective to carry out the Michael addition of indoles. β-Mono- and disubstituted enones reacted smoothly with indoles under our conditions. The cationic iron catalyst is very active, and the maximum TON was up to 425. Moreover, cationic iron-catalyzed conditions enabled a chemoselective Michael addition of a substrate possessing both enone and α,β-unsaturated ester moieties. [ABSTRACT FROM AUTHOR]

Chiral primary amine–squaramides have not been extensively studied to date in the field of organocatalysis. In this paper, novel chiral squaramides derived from natural product stevioside were developed. Both enantiomers of a series of γ-nitroaldehydes were generated by using these squaramide catalysts for the Michael addition reaction of isobutyraldehyde to nitroolefins. This asymmetric reaction proceeded well to afford the desired products in high yields (up to 98%) with high to excellent enantioselectivities (up to 99% ee). [ABSTRACT FROM AUTHOR]

In this paper, exploration of our continuous interests on late-stage derivation of quinozaline core is described. A wide array of 4-(1 H -indol-1-yl)quinazolines were obtained in good to excellent yields through palladium-catalyzed cross-coupling of 4-tosyloxyquinazolines with indole derivatives under mild reaction conditions. [ABSTRACT FROM AUTHOR]

The free-radical racemization of non-activated amines is a powerful tool for process design in the pharmaceutical industry, allowing the recycling of undesired enantiomers after chiral separation. This paper describes the development of the free-radical racemization of a key API intermediate in a continuous flow reactor. Upon development, a significant reduction of the solvent usage and radical initiator was made possible thanks to the conversion into a continuous flow mode. This intensification positively impacted both the environmental footprint and the safety of the reaction as well as maintaining satisfactory productivity. [ABSTRACT FROM AUTHOR]

The transition-metal complexes of phosphine and secondary phosphine oxide compounds can be used in various catalytic reactions. In this paper, the synthesis and characterization of eight new crown ethers containing trivalent phosphorus in their macroring are reported. These macrocycles are promising candidates as ligands for catalytic reactions. [ABSTRACT FROM AUTHOR]

The development of catalyst-controlled, site-selective C(sp3)–H functionalization reactions is currently a major challenge in organic synthesis. In this paper, a novel bond-weakening catalyst that recognizes the hydroxy group of alcohols through formation of a borate is described. An electron-deficient borinic acid–ethanolamine complex enhances the chemical yield of the α-C–H alkylation of alcohols when used in conjunction with a photoredox catalyst and a hydrogen atom transfer catalyst under irradiation with visible light. This ternary hybrid catalyst system can, for example, be applied to functional-group-enriched- peptides. [ABSTRACT FROM AUTHOR]

Metal-catalysed carbenoid chemistry can be exploited for the synthesis of diverse ranges of small molecules from α-diazo carbonyl compounds. In this paper, three synthetic approaches to α-diazo amides are described, and their scope and limitations are determined. On the basis of these synthetic studies, recommendations are provided to assist the selection of the most appropriate approach for specific classes of product. The availability of practical and efficient syntheses of diverse α-diazo acetamides is expected to facilitate the discovery of many different classes of bioactive small molecules. [ABSTRACT FROM AUTHOR]

Nitro compounds serve as valuable intermediates for pharmaceuticals, agrochemicals, dyes, and polymers. In recent years, radical nitration using tert -butyl nitrite (t -BuONO) has attracted wide attention and desirable progress has been made. On the one hand, t -BuONO is a potential active nitro radical source and can react with various functional groups. On the other hand, as a green and novel nitration reagent, t -BuONO has relatively low price and can easily produce a radical under mild conditions, which undoubtedly provides a simple and efficient way for nitration reactions. To date, some important reviews are available that summarize the synthesis of nitro compounds. To the best of our knowledge, however, there is still no review that exclusively discusses the synthesis of nitro compounds using t -BuONO through a radical strategy. Therefore, this review aims to highlight the recent advances in radical nitration using t -BuONO as nitration reagent. The main progress in this area has been presented according to the type of reaction substrates. Special attention has been paid discussion of the reaction mechanisms and selected examples of substrates have been given. We hope this paper will be a useful reference and inspiration for those who are exploring the synthesis of nitro compounds using t -BuONO. 1 Introduction 2 Radical Nitration of Alkenes 3 Radical Nitration of Aromatics 4 Radical Nitration of Alkynes 5 Radical Nitration of 1, n -Enynes 6 Radical Nitration of Alkanes 7 Summary and Perspective [ABSTRACT FROM AUTHOR]

Multicomponent reactions (MCRs) cover strategically employed chemical transformations that incorporate three or more reactants in one pot leading to a functionalized final product. Thus, it is an ideal tool to achieve high levels of complexity, diversity, yields of desired products, atom economy, and reduced reaction times. Sugars belong to the class of naturally occurring compounds with fascinating applications in the field of drug discovery due to the presence of various hydroxy groups and well-defined stereochemistry. However, their potential in MCRs has been realized only recently. This account describes recent advances in the synthesis of sugar-derived heterocycles synthesized by MCRs. We hope to encourage the synthetic and medicinal chemistry community to apply this powerful MCR chemistry to generate novel glycoconjugate challenges. 1 Introduction 2 Synthesis of Various Functionalized Sugar Compounds 2.1 Passerini and Ugi Multicomponent Reactions 2.2 Petasis Reaction 2.3 Hantzsch Reaction 2.4 Domino Ferrier–Povarov Reaction 2.5 Marckwald Reaction 2.6 Groebke–Blackburn–Bienaymé (GBB) Reaction 2.7 Prins–Ritter Reaction 2.8 Debus–Radziszewski Imidazole Synthesis Reaction 2.9 Mannich Reaction 2.10 A3-Coupling Reaction 2.11 [3+2]-Cycloaddition Reactions 2.12 Miscellaneous Reactions 3 Conclusion [ABSTRACT FROM AUTHOR]

The paper describes the synthesis of two regioisomeric 2- amino-3-formyl- and 3-amino-2-formyl-substituted derivatives of tetrahydrobenzo[b]thiophene and their subsequent thermally initiated reactions with secondary amines to give azomethine ylides that undergo intramolecular 1,3-dipolar cycloadditions. In this way, two series of new fused heterocyclic compounds with three stereogenic centers were prepared. The compounds were identified and their structures were determined. [ABSTRACT FROM AUTHOR]

The reaction of pyrazines with 2,5-norbornadiene, an acetylene precursor, as a cascade of Diels–Alder reactions is reported yielding substituted pyridines. In contrast to the known examples of intermolecular Diels–Alder type reaction of pyrazines with acetylene, which usually leads to a mixture of products, in our case the formation of a single isomer was observed. The proposed approach allows the conversion of pyrazines with different types of substitution, except those containing methyl and amino donor groups, to pyridines. In addition, highly functionalized aminonicotic esters were obtained, which can be used for the synthesis of bioactive compounds. An unusual course of the Diels–Alder reaction was found in the case of tetrasubstituted pyrazines, which cleave organic nitriles instead of HCN. Quantum-chemical modeling of possible transition states showed that this Diels–Alder reaction proceeds via cycloaddition of 2,5-norbornadiene to pyrazine with sequential elimination of HCN and cyclopentadiene; the reaction pathway including initial formation of acetylene from norbornadiene and subsequent Diels–Alder reaction with the acetylene was rejected as kinetically unfavorable. [ABSTRACT FROM AUTHOR]

The equistoichiometric three-component reaction of an acid chloride, an alkyne, and an ortho -amino- or ortho -hydroxyphenylboronic ester proceeds smoothly to give phenanthridines or benzo[ c ]chromenes, respectively, with good to quantitative yields in the sense of a Sonogashira–Suzuki–Michael cyclization sequence. In the coupling of ortho -amidophenylboronates, interestingly, after ring closure a subsequent an acyl migration occurs to give 6-(2-(acyloxy)vinyl)phenanthridines. [ABSTRACT FROM AUTHOR]

A novel and efficient synthesis of 3- and 2-substituted indoles starting from 2-(2-nitro-1-phenylethyl or 2-nitro-1-alkyl)cyclohexanones and 1,4-diketones, respectively, using a catalytic amount of Pd/C and 1-octene system is reported. [ABSTRACT FROM AUTHOR]

Unusual amino acids have arisen as an indispensable instrument at the disposal of modern medicinal chemistry. While extensively exploited as building blocks in the search for new pharmaceuticals, their application goes far beyond. They are currently involved in explorations of the structure and conformational mobility of peptides, modification and amplification of peptidomimetic activity, and others. Herein, we report an effective synthetic approach to nonplanar, conformationally restricted, sp 3 -enriched spirocyclic α-prolines. The protocol employs readily available nitrile-based starting materials and conventional experimental procedures. The synthetic sequence is concise and includes three principal stages (one of them a four-step telescopic process). The reactions proceed on a multigram scale affording the target prolines in overall good yields. The possibility of chiral separation of the synthesized racemic spiro prolines to both pure enantiomers is shown. The building blocks synthesized in the study are expected to have practical uses in the field of medicinal chemistry. [ABSTRACT FROM AUTHOR]