Showing papers on "Intramolecular reaction published in 2009"
TL;DR: A detailed mechanistic investigation of the intramolecular dirhodium tetracarboxylate-catalyzed sulfamate ester C-H amination reaction is presented in this article.
204 citations
TL;DR: Operationally simple Au(I)-catalyzed intramolecular hydroarylation reactions of terminal alkynes that proceed in high yield and under very mild conditions are described.
Abstract: Operationally simple Au(I)-catalyzed intramolecular hydroarylation (IMHA) reactions of terminal alkynes that proceed in high yield and under very mild conditions are described. These processes involve low catalyst loadings, mild reaction temperatures, and short reaction times, require no cocatalysts or additives, and allow for the generation of a number of important heterocyclic motifs from readily accessible starting materials.
162 citations
TL;DR: Data suggest that electronic donation by the biaryl pi-system accelerates the formation of rhodium nitrenoid and that C-N bond formation occurs through a 4pi-electron-5-atom electrocyclization.
Abstract: The use of a rhodium(II) carboxylate catalyst enables the mild and stereoselective formation of carbazoles from biaryl azides. Intramolecular competition experiments of triaryl azides suggested the source of the selectivity. A primary intramolecular kinetic isotope effect was not observed, and correlation of the product ratios with Hammett σ+ values produced a plot with two intersecting lines with opposite ρ values. These data suggest that electronic donation by the biaryl π-system accelerates the formation of rhodium nitrenoid and that C−N bond formation occurs through a 4π-electron-5-atom electrocyclization.
125 citations
TL;DR: A simple and convenient copper-catalyzed method for the synthesis of quinoline-2-carboxylate derivatives through sequential intermolecular addition of alkynes onto imines and subsequent intramolecular ring closure by arylation is developed.
Abstract: We developed a simple and convenient copper-catalyzed method for the synthesis of quinoline-2-carboxylate derivatives through sequential intermolecular addition of alkynes onto imines and subsequent intramolecular ring closure by arylation. The efficiency of this system allowed the reactions to be carried out at room temperature.
117 citations
TL;DR: Through an intramolecular C-C bond formation of diarylamines by the S(RN)1 mechanism, carbazoles were achieved and substituted 9H-carbazoles, benzocarbazoles and even 3,3'-bi(9H- carbazole) were obtained by a double S( RN)1 reaction with benzidine.
Abstract: The synthesis of a series of substituted 9H-carbazoles by the photostimulated SRN1 substitution reaction with diarylamines as starting substrate was performed. The diarylamines were obtained by two approaches, the Pd-catalyzed reactions (Buchwald−Hartwig) or Cu-catalyzed reactions of 2-haloanilines with aryl halides, or 2-bromoiodobenzene with anilines, with moderate to very good isolated yields (45−89%). Through an intramolecular C−C bond formation of diarylamines by the SRN1 mechanism, carbazoles were achieved. These reactions proceeded synthetically in very good to excellent yields (81−99%) in liquid ammonia and DMSO. The reaction of N-(2-bromophenyl)-2-phenylbenzenamine gave 1-phenyl-9H-carbazole (38%) and the isomer 9H-tribenz[b,d,f]azepine (58%). By using this methodology, 9H-carbazoles, substituted 9H-carbazoles, benzocarbazoles, and even 3,3′-bi(9H-carbazole) were obtained by a double SRN1 reaction with benzidine.
109 citations
TL;DR: A novel and efficient one-pot synthesis of various N-substituted 2-heterobenzimidazoles has been developed through a Cu(I)-catalyzed cascade intermolecular addition/intramolecular C-N coupling process.
Abstract: A novel and efficient one-pot synthesis of various N-substituted 2-heterobenzimidazoles has been developed. Through a Cu(I)-catalyzed cascade intermolecular addition/intramolecular C−N coupling process, a wide variety of 2-heterobenzimidazoles could be synthesized from o-haloarylcarbodiimides and N- or O-nucleophiles.
98 citations
TL;DR: The utility of this N-heterocyclic ring forming strategy as a synthetic tool that makes use of alcohols as pro-electrophiles was exemplified by its application to the synthesis of the bioactive tetrahydroquinoline alkaloid (+/-)-angustureine.
Abstract: An efficient synthetic route to 1,2-dihydroquinolines that relies on AuCl3/AgSbF6-catalyzed intramolecular allylic amination of 2-tosylaminophenylprop-1-en-3-ols is described herein. Uniquely, the reactions were found to only proceed rapidly at room temperature in the presence of the gold and silver catalyst combination and produce the 1,2-dihydroquinoline products in yields of 40−91%. The method was shown to be applicable to a broad range of 2-tosylaminophenylprop-1-en-3-ols containing electron-withdrawing, electron-donating, and sterically demanding substrate combinations. The mechanism is suggested to involve activation of the alcohol substrate by the AuCl3/AgSbF6 catalyst. This is followed by ionization of the starting material, which causes intramolecular nucleophilic addition of the sulfonamide unit to the allylic cation moiety and construction of the 1,2-dihydroquinoline. The utility of this N-heterocyclic ring forming strategy as a synthetic tool that makes use of alcohols as pro-electrophiles was...
98 citations
TL;DR: While microwave irradiation was found to be determinant on the reaction efficiency, the choice of ligand diverged the reaction pathways and intramolecular alpha-CH arylation of tertiary amide occurred to furnish the oxindoles.
Abstract: Linear amides 4, prepared in one step by the Ugi four-component reaction, were converted to 3,4-dihydroquinoxalin-3-ones (5) or to 2-(2-oxoindolin-1-yl)acetamides (6) dependent on the catalytic conditions. While microwave irradiation was found to be determinant on the reaction efficiency, the choice of ligand diverged the reaction pathways. Heating a solution of 4 in dioxane/MeCN (v/v = 85/15) under microwave irradiation conditions in the presence of Pd(dba)2 (0.05 equiv) and Cs2CO3 (2 equiv), using XPhos as a supporting ligand, afforded the 3,4-dihydroquinoxalin-3-ones (5) via an intramolecular N-arylation of the secondary amide. On the other hand, using BINAP as ligand under otherwise identical conditions, intramolecular α-CH arylation of tertiary amide occurred to furnish the oxindoles (6).
96 citations
TL;DR: It was found that there is a slight increase in the amount of B-N dative bonding on going from a tertiary to a secondary to a primary amine group, but that solvent insertion dominates in all cases of the boronate esters.
Abstract: This work investigates the interplay between the intramolecular B-N dative bonding and solvent insertion in various ortho-methylamino arylboronic acids in protic media. (11)B NMR experiments were conducted to study the effect that the degree of substitution of the amine group has on B-N bonding versus solvent insertion. It was found that there is a slight increase in the amount of B-N dative bonding on going from a tertiary to a secondary to a primary amine group, but that solvent insertion dominates in all cases of the boronate esters. A X-ray crystal structure gives further insight into the structure of the solvent-inserted boronate esters, showing that the inserted solvent has its hydrogen primarily on the amine. Lastly, studies of the use of boronate esters as receptors for simple alcohols and carboxylic acids are described.
94 citations
TL;DR: Efficient synthetic routes to pyrazolo[3,4-b]indoles and pyrazol[1,5-a]benzimidazoles via intramolecular palladium- and copper-catalyzed cyclization of 1-aryl/1-unsubstituted 5-(2-bromoanilino)pyrazole precursors via intramsolecular C-C and C-N bond formation have been reported.
Abstract: Efficient synthetic routes to pyrazolo[3,4-b]indoles and pyrazolo[1,5-a]benzimidazoles via intramolecular palladium- and copper-catalyzed cyclization of 1-aryl/1-unsubstituted 5-(2-bromoanilino)pyrazole precursors via intramolecular C-C and C-N bond formation have been reported.
94 citations
TL;DR: A highly efficient Cu-catalyzed C-O bond-forming reaction of alcohol and aryl bromides has been developed through the use of copper(I) iodide as a catalyst, 8-hydroxyquinoline as a ligand, and K(3)PO(4) as a base.
Abstract: A highly efficient Cu-catalyzed C−O bond-forming reaction of alcohol and aryl bromides has been developed. This transformation was realized through the use of copper(I) iodide as a catalyst, 8-hydroxyquinoline as a ligand, and K3PO4 as a base. A variety of functionalized substrates were found to react under these reaction conditions to provide products in good to excellent yields.
TL;DR: Biindolizines were synthesized under mild conditions with excellent regioselectivity in high yields through palladium-catalyzed C-H functionalization of indolizine and synthesis of a macrocyclic compound was also achieved via intramolecular double C- H functionalization.
Abstract: Biindolizines were synthesized under mild conditions with excellent regioselectivity in high yields through palladium-catalyzed C-H functionalization of indolizines. Synthesis of a macrocyclic compound was also achieved via intramolecular double C-H functionalization.
TL;DR: Some complex pyrano[2,3b]- and pyrido [2, 3b]-quinolines were synthesized from simple acetanilides via intramolecular domino hetero Diels-Alder reactions of 1-oxa-1,3-butadienes using water as solvent as discussed by the authors.
TL;DR: The development of enantiomerically-resolved, axially-chiral seven-membered N-heterocyclic carbene ((7)NHC) ligands for palladium is described and catalytic data compare favorably to results obtained with a Pd(II) catalyst bearing a chiral five- Membered-ring NHC ligand are highlighted to highlight the potential significance of this new class of chiral N HC ligands.
TL;DR: Catalytic asymmetric synthesis of neolignan natural products (-)-epi-conocarpan and (+)-conOCarpan has been achieved by exploiting an enantio- and diastereoselective intramolecular C-H insertion reaction to construct a cis-2-aryl-2,3-dihydrobenzofuran ring system as a key step.
Abstract: Catalytic asymmetric synthesis of neolignan natural products (−)-epi-conocarpan and (+)-conocarpan has been achieved by exploiting an enantio- and diastereoselective intramolecular C−H insertion reaction to construct a cis-2-aryl-2,3-dihydrobenzofuran ring system as a key step. The C−H insertion reaction of 5-bromoaryldiazoacetate catalyzed by Rh2(S-PTTEA)4, a new dirhodium(II) carboxylate complex that incorporates N-phthaloyl-(S)-triethylalaninate as chiral bridging ligands, provided 2-aryl-5-bromo-3-methoxycarbonyl-2,3-dihydrobenzofuran with exceptionally high diastereoselectivity (cis/trans = 97:3) and high enantioselectivity for the cis isomer (84% ee).
TL;DR: The hydroamination of alkynyl carbamates bearing an acetal or enone was successfully applied to the concise synthesis of tetracyclic heterocycles such as nitidine via the single catalyst-mediated tandem cyclization which consists of a condensation or a Michael addition of the resulting enecarbamates.
Abstract: As a convenient and direct synthesis of 1,2-dihydroisoquinolines, the gold(I)-catalyzed intramolecular hydroamination of (2-alkynyl)benzyl carbamates has been developed. The reaction with cationic gold(I) complex [AuCl(PPh3)/AgNTf2] proceeded at room temperature, giving the desired 6-endo adducts. The addition of alcohol efficiently promoted the reaction, and the amount of the catalyst could be reduced to 1 mol %. However, the alkynes bearing either an electron-deficient aryl group or an alkyl group resulted in predominant production of 5-exo adducts. In such cases, use of a bulky gold catalyst, AuCl[(o-biPh)(tBu)2P]Cl/AgNTf2, improved the regioselectivity, giving the 6-endo adducts in better yields. Furthermore, the hydroamination of alkynyl carbamates bearing an acetal or enone was successfully applied to the concise synthesis of tetracyclic heterocycles such as nitidine via the single catalyst-mediated tandem cyclization which consists of a condensation or a Michael addition of the resulting enecarbamates.
TL;DR: In this paper, a mild and efficient methodology for the synthesis of oxygenated carbazoles from diarylamines under non-acidic conditions was developed, based on a palladium-catalyzed, microwave-assisted double C-H bond activation process.
TL;DR: An efficient copper-catalyzed intramolecular arylation of formamidines forming 2-unsubstituted benzimidazoles in excellent yields is reported.
Abstract: An efficient copper-catalyzed intramolecular arylation of formamidines forming 2-unsubstituted benzimidazoles in excellent yields is reported. Sixteen examples bearing sterically demanding substituents on nitrogen like Mes, 2,6-diisopropylphenyl, or 2-tert-butylphenyl and tolerating various functional groups demonstrate the utility of this method.
TL;DR: A novel route to 2,3-substituted benzo[b]thiophenes by intramolecular radical cyclization of polarized ketene dithioacetals derived from o-bromoarylacetonitriles or the corresponding 3-(methylthio)-3-alkyl/aryl/heteroaryl analogues has been reported.
Abstract: A novel route to 2,3-substituted benzo[b]thiophenes by intramolecular radical cyclization of polarized ketene dithioacetals derived from o-bromoarylacetonitriles or the corresponding 3-(methylthio)-3-alkyl/aryl/heteroaryl analogues has been reported.
TL;DR: 2, 3-Dichloro- and 2,3-dibromopyridines have been shown to react with readily available anilines to obtain various substituted alpha-carbolines in moderate to excellent yields.
Abstract: A one-pot synthesis of α-carbolines via a palladium-catalyzed aryl amination followed by intramolecular arylation is described. 2,3-Dichloro- and 2,3-dibromopyridines have been shown to react with readily available anilines to obtain various substituted α-carbolines in moderate to excellent yields.
TL;DR: The power of the chemistry was demonstrated by the synthesis of the core ring systems of the alkaloids (+/-)-scandine and (+/--myrioneurinol and the total syntheses of the Alkenes, including the formation of five- and six-membered rings for the other two new ring sizes.
Abstract: The preparation of tricyclic amines from acyclic precursors is described using a cascade of tandem reactions involving condensation of an aldehyde with a primary amine, cyclization (with displacement of a halide), and then in situ deprotonation or decarboxylation to give an azomethine ylide or nitrone followed by intramolecular dipolar cycloaddition. The methodology is straightforward, and the aldehyde precursors are prepared easily and quickly in high yield using nitrile alkylations followed by DIBAL-H reduction. The relative ease of reaction of various substrates with different tether lengths between the aldehyde and the halide or dipolarophile has been studied. Several primary amines including simple amino acids such as glycine, alanine, and phenylalanine and derivatives such as glycine ethyl ester and also hydroxylamine have been investigated. High yields are obtained in the formation of different tricyclic ring sizes; the dipolar cycloaddition necessarily creates a five-membered ring, and we have inv...
TL;DR: In the presence of Pd(OAc)(2) and dppf, a variety of N-arylpropiolamides successfully underwent the intramolecular hydroarylation reaction to afford the corresponding 3-(monosubstituted-methylene)oxindoles in moderate to excellent yields.
Abstract: Palladium-catalyzed intramolecular hydroarylation of N-arylpropiolamides has been developed for the stereoselective synthesis of 3-(monosubstituted methylene)oxindoles. In the presence of Pd(OAc)2 and dppf, a variety of N-arylpropiolamides successfully underwent the intramolecular hydroarylation reaction to afford the corresponding 3-(monosubstituted-methylene)oxindoles in moderate to excellent yields. It is noteworthy that the stereoselectivity of the reaction can be controlled by varying the reaction temperature.
TL;DR: A base-catalyzed condensation of phenyl acetate with acid chloride leads to the first total synthesis of psoralidin, a natural product with a broad range of biological activities, in a highly convergent and regioselective manner.
Abstract: A base-catalyzed condensation of phenyl acetate with acid chloride, followed by intramolecular cyclization and microwave-assisted cross-metathesis reaction, leads to the first total synthesis of psoralidin, a natural product with a broad range of biological activities, in a highly convergent and regioselective manner.
TL;DR: From this key intermediate, an intramolecular vinyl halide Heck reaction accomplished the closure of the strained 1-azabicyclo[4.2.2]decane framework of the alkaloid with concomitant incorporation of the exocyclic alkylidene substituents.
Abstract: An indole-templated ring-closing metathesis or a 2-indolylacyl radical cyclization constitute the central steps of two alternative approaches developed to assemble the tricyclic ABC substructure of the indole alkaloid apparicine. From this key intermediate, an intramolecular vinyl halide Heck reaction accomplished the closure of the strained 1-azabicyclo[4.2.2]decane framework of the alkaloid with concomitant incorporation of the exocyclic alkylidene substituents.
TL;DR: Cis-4-(1-chloro-1-methylethyl)-1-{omega-[(tert-butoxycarbonyl)amino]alkyl}azetidin-2-ones were diastereoselectively transformed into novel trans- 1-aza-4-oxabicyclo[3.3.0]octan-8-ones and trans-1,5-diazabicyClo[4
Abstract: cis-4-(1-Chloro-1-methylethyl)-1-(omega-hydroxyalkyl)azetidin-2-ones were diastereoselectively transformed into novel trans-1-aza-4-oxabicyclo[3.3.0]octan-8-ones and trans-1-aza-5-oxabicyclo[4.3.0]nonan-9-ones upon treatment with 1 equiv of AgBF4 and pyridine in toluene via intramolecular nucleophilic trapping of N-acyliminium intermediates by the hydroxyl moiety. Additionally.. the corresponding aza-analogues of the aforementioned bicyclic gamma-lactams (i.e., trans-1,4-diazabicyclo[3.3.0] octan-8-ones and trans-1,5diazabicyclo[4.3.0]nonan-9-ones) were prepared in a convenient way starting from cis-4-(1-chloro-1-methylethyl)-1-{omega-[(tert-butoxycarbonyl)amino]alkyl)azetidin-2-ones applying the same reaction conditions. The intermediate N-acyliminium ions were formed by ring expansion of the starting beta-lactams through generation of a transient silver(I)-induced carbenium ion.
TL;DR: An asymmetric synthesis of the ABCD ring system of daphnilactone B with methyl substituent on the A ring installed in the correct configuration via hydrogenation of an exocyclic olefin in the final step.
TL;DR: In this paper, the insertion of nitrene species into an allylic C-H bond of silyl enol ethers has been shown to yield an advanced intermediate in Overman's synthesis of the montanine-type Amaryllidaceae alkaloid (−)-pancracine.
TL;DR: An N-heterocyclic carbene (NHC) catalyzed intramolecular lactonization to prepare densely functionalized bicyclic γ-lactam-γ- lactone adducts from enals is reported.
TL;DR: The nucleophilic substitution of alkyl fluorides was achieved in the intramolecular reactions with O- and N-nucleophiles in a manner influenced by the nature of nucleophiles, the size of the ring to be formed, and the comformational rigidity of the precursors.
Abstract: The nucleophilic substitution of alkyl fluorides was achieved in the intramolecular reactions with O- and N-nucleophiles. The intramolecular defluorinative cyclization reaction was influenced by the nature of nucleophiles, the size of the ring to be formed, and the comformational rigidity of the precursors. Intermolecular nucleophilic substitution reactions of alkyl fluorides under similar reaction conditions were found to be difficult. The stereochemistry study of the current C-F bond cleavage reaction showed a complete configurational inversion, which supports an intramolecular S(N)2 reaction mechanism.
TL;DR: In this paper, Lewis acid-catalyzed reactions of dialkyl 2-arylcyclopropane-1,1-dicarboxylates with 2,5-dimethylfuran were found to give products of [3+2]-cycloaddition to C(2)-C(3) bond, which contain reactive vinyl ether moiety.