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Developing eco-friendly, stable, and easy-to-handle acyl sources is of great importance in synthetic and green chemistry. This study describes the synthesis of benzo[d]azol-2(3H)-ones such as benzo[d]thiazol-2(3H)-ones, benzo[d]oxazol-2(3H)-ones, and benzo[d]imidazol-2(3H)-ones using 2-phenoxycarbonyl-4,5-dichloropyridazin-3(2H)-one in one pot. The reaction reported is carried out under neutral or acidic conditions in the presence of zinc or sodium bicarbonate to give the corresponding heterocycles in good to excellent yields. The reaction uses a solid stable carbonyl source that is a recyclable functional-group carrier, pyridazin-3(2H)-one. [ABSTRACT FROM AUTHOR]

The first generation of 2-bromo-3-lithioquinolines can be achieved and they are utilized for the preparation of 3-substituted 2-bromoquinolines. Thus, 2-(2,2-dibromoethenyl)phenyl isocyanides are treated with butyllithium in THF at −78 °C to generate these novel lithium compounds, which are allowed to react with various electrophiles to afford the corresponding desired products in one-pot. [ABSTRACT FROM AUTHOR]

Pyrene-2-carboxylic acid is a versatile intermediate for introducing the unusual 2-pyrenyl unit into functional organic molecules. A classical preparation for this molecule has been revised and improved to give a robust and efficient three-step process. The method has been applied on a multigram scale to give pyrene-2-carboxylic acid in >70% overall yield from pyrene. [ABSTRACT FROM AUTHOR]

A series of 4-arylamino-8-(alkyl or aryl)hydrazidepyrimido[ 5,4-d]pyrimidines was obtained efficiently from 6-carbo-hydrazonamidepurines by reaction with piperidine. The 6-carbo-hydrazonamidepurines were generated selectively by the reaction of 6-imidatopurine with hydrazides under acidic conditions. [ABSTRACT FROM AUTHOR]

An overview of the most important synthetic strategies currently available for the preparation of cyclopent-2-enones is presented and illustrated with recent applications. [ABSTRACT FROM AUTHOR]

Abstract: Monoindolizinylquinoxalinepodands, easily available from indolizinylquinoxalines and various dihalides, undergo smooth oxidative dimerization in the presence of molecular iodine to afford corresponding macrocycles in good yields in a short reaction time. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient, and practical. In solution the title macrocycles exist in an equilibrium of several conformations arising from restricted rotation around the Ind–Qx bonds (ca. C2 symmetrical and nonsymmetrical forms). The population of the forms and exchange rate between them depends strongly on the spacer type (length). [Copyright &y& Elsevier]

Abstract: A series of carbamate melatonin derivatives was treated with performic acid, providing tricyclic products with a 3-hydroxytetrahydropyrrolo[2,3-b]indole skeleton. An unusual migration of carbamate groups was observed in some cases, and the reaction appeared to be strongly dependent on the type of substituent in the phenyl ring of the phenylcarbamate group. Theoretical calculations suggest that the reaction is kinetically controlled. [Copyright &y& Elsevier]

A range of 1,7-diarylheptane-1,7-diones were electrooxidized in the presence of iodide ions and a base in a mixture of methanol and toluene as the reaction solvents to give the corresponding cyclized 1,2-diaroylcyclopentanes in moderate to good yields. The reactions were carried out under extremely mild reaction conditions for which the optimal amount of electrolytic current varied from 2.05-3.17 F.mol-1 depending on the substrates. The reaction presumably proceeds through a two-electron oxidation process in which the iodide ion plays an important role as the electron carrier. [ABSTRACT FROM AUTHOR]

A simple and general 'one-pot' procedure for the synthesis of 2,9-diarylpurines with one or multiple hydroxyl groups in the 2-aryl unit is described, from the reaction of 5-amino-4-amidinoimidazoles with phenolic aldehydes. [ABSTRACT FROM AUTHOR]

A variety of 3-arylated di- and tetrahydro-2H-2-benzazepin- 1-ones were efficiently assembled through a sequence involving a Suzuki-Miyaura cross-coupling reaction with enol phosphates derived from the corresponding benzazepine-1,3-diones. This technique has been further exploited for the construction of the homoprotoberberine skeleton, which was readily accessed by intramolecular carbocationic annulation reaction applied to a suitably substituted precursor. [ABSTRACT FROM AUTHOR]

new approach to highly functionalized quinolines is proposed. This approach is based on the electrophilic recyclization of 2-[2-(acylamino)benzyl]furans under the Bischler-Napieralski reaction conditions. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of a series of benzo(iso)quinoline and phenanthroline derivatives has been achieved using an efficient one-pot procedure. It proceeds through a Suzuki–Miyaura cross-coupling followed by a Dieckmann–Thorpe ring closure under microwave irradiation and provides easy access to building blocks not readily available through other methods. [Copyright &y& Elsevier]

An asymmetric synthesis of di- and trisubstituted cyclopropanes proceeding through an intramolecular ring closure of activated chiral benzyl alcohols has been developed. The chiral alcohol intermediates are obtained from asymmetric reduction of readily available 1,4-keto esters and undergo a one-pot activation and ring closure to provide the ester-functionalized cyclopropanes in high enantio- and diastereomeric purity. This methodology avoids the use of hazardous diazo and alkyl zinc reagents commonly employed in cyclopropanation reactions. [ABSTRACT FROM AUTHOR]

1-Silaindenes are prepared starting from (2-vinylphenyl)hydrosilanes and alkynes through a ruthenium-catalyzed hydrosilylation-ring-closing-metathesis sequence. The method is successfully applied to the synthesis of molecules containing multiple silaindene units. [ABSTRACT FROM AUTHOR]

Abstract: A one-pot synthesis of novel poly-substituted phenanthrenes is described in this article through a Suzuki–Miyaura cross-coupling followed by a Dieckmann–Thorpe ring closure under microwave irradiation. The selection of the appropriate starting materials allowed us to introduce diversity on various positions of the phenanthrene ring system. [Copyright &y& Elsevier]

Abstract: A convenient synthesis of 3-arylbenzo[b]thiophenes utilizing an interrupted Pummerer reaction of 2-(1-arylvinyl)phenyl ethyl sulfoxides is described. Thus, treatment of these sulfoxides, which were readily prepared from 2-sulfanylphenyl ketones or 2-fluoro-5-methoxybenzaldehyde, with acetic anhydride at 100°C afforded 3-arylbenzo[b]thiophenes in reasonable yields. [Copyright &y& Elsevier]

The use of a commercially available thiazolium salt facilitated an intramolecular Stetter reaction between an aliphatic aldehyde and an acrylate unit, which delivered a trans,syn-fused bicyclic pyranone in high yield as a single diastereomer. The pyranone was used to synthesize a trans,syn,trans-fused polycyclic ether array and was ring expanded to give the corresponding oxepanone. [ABSTRACT FROM AUTHOR]

Nicholas reactions on 2,7-dioxygenated naphthalenes give C-1 monosubstitution and C-1/C-8 disubstitution in most �cases. From γ-carbonyl cation monocondensation product 3b or alkyne-unsubstituted dicondensation product 4a, cyclohepta[de]naphthalenes bearing no substituents, gem-dimethyl substituents, and a ketone function, and the rearranged abietane framework of microstegiol may be prepared. [ABSTRACT FROM AUTHOR]

Abstract: New examples of substituted thiazole derivatives carrying different heterocyclic ring systems at C-2 position were prepared via the reaction of several allenyl isothiocyanates with nucleophiles such as imidazoles, pyrazoles, benzimidazoles, indazole, 1,2,3-triazole, 1,2,4-triazole, and 1H-benzotriazole. Although these allenyl isothiocyanates are very reactive electrophiles and tend to polymerize, the yield of the thiazole products ranked between modest and very good. The regiochemistry of the reactions was proved by NMR and X-ray studies indicating that the attack of ambident nucleophiles proceeded very selectively. In some cases, however, the products were formed as mixtures of aromatic heterocycles and non-aromatic isomers. The latter could be rearranged to yield the uniform aromatic thiazoles. [Copyright &y& Elsevier]

The intramolecular Friedel-Crafts reaction of indole-2-carboxylic acid β-oxoamides catalyzed by trifluoroacetic acid or InCl3, is a convenient method for the synthesis of 3-aryl-, 4-aryl-, and 4-alkyl-β-carbolin-1-ones. [ABSTRACT FROM AUTHOR]

Abstract: The effects of substituents on the rate of intramolecular cyclization of the 2,5-hexadienyl radicals have been investigated computationally with DFT theory, using the UB3LYP functional. Various substituents – CN, NO2, CH3, NH2, and t-butyl – at various positions – C1, C5 and C6 – were considered in the calculations. An electron-donating substituent on the C1 position raises the radical SOMO energies to increase the interaction with the alkene LUMO, whereas an electron-withdrawing counterpart lowers the SOMO and increases the interaction with the alkene HOMO. Both interactions decrease the activation energies, by 0.9–10.2kcal/mol, and increase the rate of reaction rate, from 3 to 2.7×107 times. Similar results were obtained for the substituents at the C6 position, and the activation energies for the intramolecular cyclization were decreased by 0.2–4.8kcal/mol and the reaction rate increased from 2 to 2.8×103 times. The substituent at the C5 position favors the formation of a 6-endo product because of a steric effect. The effects of disubstituents at both C1 and C6 positions were also investigated; the results showed that the electron-withdrawing groups decrease most effectively the activation energies. The so-called captodative effect was also investigated. [Copyright &y& Elsevier]

One version of the tert-amino effect operating in tertanilines possessing an ortho-vinyl substituent affords a fused tetrahydropyridine ring by an isomerization process with the formation of a new carbon-carbon bond between the vinyl and tert-amino moieties. Since its discovery in 1984, this type of cyclization has been efficiently used for the construction of fused-ring systems. However, it has been found that the electron-deficient heterocyclic analogues of tert-anilines, such as diazines, may undergo isomerization at considerably lower reaction rates and, as a consequence, their reactions may require harsh conditions. Recent synthetic studies have indicated that the rate and yield may be improved by incorporating the γ-vinylic carbon atom into an electron-deficient ring and/or buttressing the tert-amino group, and/or performing the reaction by means of microwave irradiation. This review describes relatively recent synthetic transformations involving this type of tert-amino effect and devotes special attention to structure-reactivity relationships including regio- and stereochemical aspects. [ABSTRACT FROM AUTHOR]

Studies were made of the kinetics of methoxide ion-catalysed reactions of seven substituted phenyl N-(2-thiocarbamoylphenyl)carbamates, 4-methoxyphenyl N-(2-thiocarbamoylphenyl)-N-(methyl)carbamate and five substituted phenyl N-(4-thiocarbamoylphenyl)carbamates, leading to the respective cyclisation products (i.e. 4-thioxo-1H,3H-quinazolin-2-one or 1-methyl-4-thioxo-1H,3H-quinazolin-2-one) and/or methanolysis product, i.e. methyl N-(4-thiocarbamoylphenyl)carbamate. The comparison of the rate constants, βlg, and ρ constants of the 2-thiocarbamoyl derivatives (βlg = -1.15, ρ = 3.1 ± 0.1) and 4-thiocarbamoyl derivatives (ρ = 4.6 ± 0.2, βlg = -1.55) shows that the ring closure reaction proceeds by the BAc2 mechanism with the splitting off of phenoxide anion being the rate-limiting step, while the methanolysis follows the E1cB mechanism. The ring closure reaction of 4-methoxyphenyl N-(2-thiocarbamoyl)-N-(methyl)carbamate proceeds kinetically in two steps, the respective rate constants differing by one order of magnitude. The NMR spectrum, spectral record and computational calculations of the ring closure reaction indicate that the process involves parallel reactions of two rotamers formed due to hindered rotation. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A ring-closing olefin metathesis is the key step in the synthesis of the β-bisabolols. [ABSTRACT FROM AUTHOR]

Abstract: The new ring-fused azepino[5,6-b]indole derivatives 3, 4 and 5 were prepared from diene precursors 8, 9, 13 and 15 in fair yields via a final ring-closing olefin metathesis. [Copyright &y& Elsevier]

Reaction of C-2 substituted cyclohexenone with an enantiomerically pure α-bromopentenoate leads to enantiopure tricyclooctane, which can be transformed into a taxoid like compound having the typical bicyclo[5.3.1]undecane skeleton. [Copyright &y& Elsevier]

A stereoselective synthesis of functionalized 2-oxo-1-azabicyclo[5.3.0]alkane is presented. Key events of the synthetic sequence were the stereoselective propenylation of an N-acyliminium ion and a ring-closing metathesis reaction forming a 7-membered lactam. [ABSTRACT FROM AUTHOR]

Abstract: We report here an application of a furan ring opening-Paal–Knorr pyrrole synthesis sequence for the transformation of furfurylamines into 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazin-3-ones. [Copyright &y& Elsevier]

Novel 6-substituted 5-alkoxy(benzyloxy)-3,6-dihydro-2H-1,3,4-oxadiazin-2-ones have been prepared in good yields and very short reaction times by intramolecular cyclization of α-hydroxyhydrazonates in the presence of sodium ethoxide under microwave irradiation. [ABSTRACT FROM AUTHOR]

Abstract: A molecular rearrangement observed during the Birch reduction of dibenzothiophene and 4,6-dimethyl-dibenzothiophene was explored and a mechanism for the rearrangement has been proposed. [Copyright &y& Elsevier]

A simple synthesis of 1,2-dithiolan-3-ones from α,β-unsaturated thiophenyl esters has been elaborated. With the aim of introducing the biologically active 1,2-dithiolan-3-one-1-oxide moiety of leinamycin into a nucleoside, the method was successfully applied to thymidine-5′-aldehyde. [Copyright &y& Elsevier]