Showing papers on "Intramolecular reaction published in 2011"
TL;DR: A straightforward, efficient, and more sustainable copper-catalyzed method has been developed for intramolecular N-arylation providing the benzimidazole ring system, exclusively carried out in water, rendering the methodology highly valuable from both environmental and economical points of view.
Abstract: A straightforward, efficient, and more sustainable copper-catalyzed method has been developed for intramolecular N-arylation providing the benzimidazole ring system. With Cu2O (5 mol %) as the catalyst, DMEDA (10 mol %) as the ligand, and K2CO3 as the base, this protocol was applied to synthesize a small library of benzimidazoles in high yields. Remarkably, the reaction was exclusively carried out in water, rendering the methodology highly valuable from both environmental and economical points of view.
161 citations
TL;DR: An iron-catalyzed intramolecular alkyne-aldehyde metathesis strategy of the alkynyl ether of salicylaldehyde derivatives has been developed which works under mild reaction conditions to produce the functionalized 2H-chromene derivatives.
Abstract: An iron-catalyzed intramolecular alkyne−aldehyde metathesis strategy of the alkynyl ether of salicylaldehyde derivatives has been developed which works under mild reaction conditions to produce the functionalized 2H-chromene derivatives. This protocol is compatible toward a wide range of functional groups, such as methoxy, fluoro, chloro, bromo, and phenyl groups. This method provides an atom-economical and environmentally friendly approach for the synthesis of a series of substituted 2H-chromenes.
106 citations
TL;DR: The photoinduced reaction of o-ethenylaryl isocyanides with organic disulfides in the presence of diphenyl ditellurides affords the corresponding bisthiolated indole derivatives via a radical cyclization process and affords tetracyclic compounds in one portion.
Abstract: Photoinduced reaction of o-ethenylaryl isocyanides with organic disulfides in the presence of diphenyl ditellurides affords the corresponding bisthiolated indole derivatives via a radical cyclization process. The cyclization can proceed at room temperature upon visible-light irradiation and exhibits good tolerance to functional groups. Several organic disulfides also can be employed for this cyclization, and the corresponding bisthiolated indole derivatives are obtained selectively. In addition, the photoinduced reaction of o-ethenylaryl isocyanides with bis(2-aminophenyl) disulfide affords tetracyclic compounds in one portion.
75 citations
TL;DR: The abilities of some of these molecules to function as colorimetric and luminescent pH sensors were demonstrated with dramatic color changes and Luminescence switching upon the introduction of acid.
Abstract: A series of 4-arylvinyl-2,6-di(pyridin-2-yl)pyrimidines have been efficiently prepared by a double cross-coupling reaction between 2,4-dichloro-6-methylpyrimidine and 2-(tributylstannyl)pyridine, followed by aldol condensation with the appropriate aromatic aldehyde substituted with electron-donating, electron-withdrawing, dendritic, or water-soluble groups The effect of different protic and aprotic solvents on the optical absorption and emission properties of these systems was studied Compounds with electron-donating groups display strong emission solvatochromism, suggesting the formation of an intramolecular charge-separated emitting state The solvatochromic behavior depends not only on the solvent polarity but also on the hydrogen bonding parameters of the solvent The effect of protonation was also studied, and the abilities of some of these molecules to function as colorimetric and luminescent pH sensors were demonstrated with dramatic color changes and luminescence switching upon the introduction of acid
73 citations
TL;DR: Data support a stepwise catalytic mechanism that consists of steady-state formation of a Pd(II)-amidate-alkene chelate with release of 1 equiv of pyridine and AcOH from the catalyst center, and natural charges and bond lengths of the alkene-insertion transition state suggest that this reaction is best described as an intramolecular nucleophilic attack of the amidate ligand on the coordinated alkene.
Abstract: Wacker-type oxidative cyclization reactions have been the subject of extensive research for several decades, but few systematic mechanistic studies of these reactions have been reported. The present study features experimental and DFT computational studies of Pd(OAc)2/pyridine-catalyzed intramolecular aerobic oxidative amination of alkenes. The data support a stepwise catalytic mechanism that consists of (1) steady-state formation of a PdII-amidate−alkene chelate with release of 1 equiv of pyridine and AcOH from the catalyst center, (2) alkene insertion into a Pd−N bond, (3) reversible β-hydride elimination, (4) irreversible reductive elimination of AcOH, and (5) aerobic oxidation of palladium(0) to regenerate the active trans-Pd(OAc)2(py)2 catalyst. Evidence is obtained for two energetically viable pathways for the key C−N bond-forming step, featuring a pyridine-ligated and a pyridine-dissociated PdII species. Analysis of natural charges and bond lengths of the alkene-insertion transition state suggest t...
67 citations
TL;DR: The intramolecular cyclization of o-alkynylaryl isocyanides proceeds to afford the corresponding 2,4-diiodoquinolines in good yields, which can be employed in transition metal-catalyzed cross-coupling reactions.
Abstract: Upon photoirradiation of o-alkynylaryl isocyanides in the presence of iodine, the intramolecular cyclization of o-alkynylaryl isocyanides proceeds to afford the corresponding 2,4-diiodoquinolines in good yields. 2,4-Diiodoquinolines can be employed in transition metal-catalyzed cross-coupling reactions.
66 citations
TL;DR: A new approach to functionalized fulvenes with an enone or enal moiety has been developed through gold-catalyzed intramolecular cycloisomerization of furan/ynes with a two-carbon tether in between the furan and the triple bond.
Abstract: A new approach to functionalized fulvenes with an enone or enal moiety has been developed through gold-catalyzed intramolecular cycloisomerization of furan/ynes with a two-carbon tether in between the furan and the triple bond. The reaction proceeds with complete regioselectivity via a 6-endo-cyclization and high stereoselectivity. Moreover, the E- or Z-stereochemistry of the double bond in fulvene products can be easily controlled by performing the reaction in different solvents.
59 citations
TL;DR: Both aliphatic and aromatic thiols are compatible with this process, delivering the corresponding heterocycles with good diversity.
Abstract: Condensation of carbon disulfide with thiols in the presence of K(2)CO(3) generates carbonotrithioate salts in situ, which undergo coupling with 2-iodoanilines and subsequent intramolecular condensation and elimination under assistance of CuBr to afford 2-thio-substituted benzothiazoles. Both aliphatic and aromatic thiols are compatible with this process, delivering the corresponding heterocycles with good diversity.
55 citations
TL;DR: In this article, an organocatalytic intramolecular Stetter-type hydroacylation reaction between an aldehyde and an activated alkyne has been developed, which induces salicylaldehyde-derived alkynes derivatives to assemble into a series of chromone derivatives using a catalytic amount of thiazolium-based carbene catalyst.
Abstract: An organocatalytic intramolecular Stetter-type hydroacylation reaction between an aldehyde and an activated alkyne has been developed. This study induces salicylaldehyde-derived alkyne derivatives to assemble into a series of chromone derivatives using a catalytic amount of thiazolium-based carbene catalyst.
54 citations
TL;DR: The copper-catalyzed tandem reaction of isocyanides with N-(2-haloaryl)propiolamides is very efficient for the synthesis of pyrrolo[3, 2-c]quinolin-4-ones and offered an efficient method for constructing fused pyrrole structures.
Abstract: The copper-catalyzed tandem reaction of isocyanides with N-(2-haloaryl)propiolamides is very efficient for the synthesis of pyrrolo[3, 2-c]quinolin-4-ones. Highly reactive cyclic organocopper intermediates were proposed to be generated in the copper-catalyzed formal [3 + 2] cycloaddition reaction of isocyanides with triple bonds. Intramolecular trapping of the organocopper intermediates can lead to aryl C-C bond formation, which offered an efficient method for constructing fused pyrrole structures.
51 citations
TL;DR: The electroreductive intramolecular coupling of phthalimides with aromatic aldehydes in the presence of chlorotrimethylsilane and triethylamine led to five-, six-, and seven-membered cyclized products.
Abstract: The electroreductive intramolecular coupling of phthalimides with aromatic aldehydes in the presence of chlorotrimethylsilane and triethylamine led to five-, six-, and seven-membered cyclized products (58-84%). The electroreductive cyclization was applied to the total synthesis of lennoxamine.
TL;DR: A series of 2,3,4-trisubstituted 3,4dihydroquinazoline 3 was prepared by intramolecular aza-Wittig reaction of amide carbonyl groups with methyldiphenyl iminophosphorane, which was obtained from a Ugi 4CC/Staudinger sequence.
TL;DR: In this article, a new C-C bond forming reaction leading to adjacent quaternary carbons is reported, which is a one-pot hydride shift/cyclization process facilitated by the hydricity of the acetalic C-H bonds.
Abstract: A new C—C bond forming reaction leading to adjacent quaternary carbons is reported. It is a one-pot hydride shift/cyclization process facilitated by the hydricity of the acetalic C—H bonds, with benzylidenemalonate fragments as electrophilic hydride acceptors, and the catalysis of scandium(III) triflate. The reaction products are 1,2-dihydroindane derivatives. Alkoxy and alkanethiolate groups can be also intramolecularly transferred from the acetalic carbon to the electrophilic benzylidenemalonate C=C bond.
TL;DR: Addition of hydroxylamine to substituted 4-chlorobutanals gives intermediate nitrones that undergo tandem cyclization and then intramolecular dipolar cycloaddition to give the core ring system of the yuzurimine-type natural products.
Abstract: Addition of hydroxylamine to substituted 4-chlorobutanals gives intermediate nitrones that undergo tandem cyclization and then intramolecular dipolar cycloaddition to give the core ring system of the yuzurimine-type natural products. Ring-opening of the isoxazolidines gives amino alcohols that can be converted to 1,3-oxazines, representing the tetracyclic core of alkaloids such as daphcalycic acid and daphcalycine.
TL;DR: Two new polyhydroxylated nortropane analogues closely related with Calystegines have been prepared in excellent chemical yields and complete selectivity through the recently confirmed thermally induced 2-aza-Cope rearrangement of nitrones.
Abstract: Two new polyhydroxylated nortropane analogues closely related with Calystegines have been prepared in excellent chemical yields and complete selectivity. A synthetic strategy based on consecutive nucleophilic allylation, oxidation, and intramolecular dipolar cycloaddition was developed. The formation of key intermediate cycloadducts were observed to take place through the recently confirmed thermally induceded 2-aza-Cope rearrangement of nitrones.
TL;DR: Alkynylaziridines carrying an aryl group could be efficiently converted to spiro[isochroman-4,2'-pyrrolines] with gold salts as catalysts with dual σ and π Lewis acidities of gold.
TL;DR: The parent 1-isoindolinone was obtained in a facile, highly chemoselective intramolecular aminocarbonylation of 2-iodobenzylamine and the mechanistic details of the ring-closure reaction and the conditions leading to side-products are discussed.
TL;DR: In this paper, a Pd-catalyzed intramolecular acetylene hydroarylation protocol was used for the synthesis of the azocino[b]indole framework.
TL;DR: In this paper, an efficient direct synthesis of oxazolidinones fused to six-membered heterocyclic rings starting from carbamate-protected aminoalkenes has been developed.
Abstract: An efficient, direct synthesis of oxazolidinones fused to six-membered heterocyclic rings starting from carbamate-protected aminoalkenes has been developed. This procedure is based on an oxidative palladium(II)-catalyzed reaction performed in the presence of stoichiometric copper chloride, which is determinant to promote the formation of the bicyclic product and prevent the isolation of the monocyclic amination product. Oxazolidinone compounds arise from a domino aminocarboxylation process through the direct intervention of the carbamate oxygen after the initial palladium-promoted transfer of the nitrogen atom on the C=C double bond.
TL;DR: A computational study of the mechanism of the intramolecular carboalkoxylation of alkynes reported by Toste et al. allows the characterization of the chirality transfer process that makes this reaction enantioselective.
Abstract: A computational study of the mechanism of the intramolecular carboalkoxylation of alkynes reported by Toste et al. allows the characterization of the chirality transfer process that makes this reaction enantioselective. Memory of chirality is preserved up until the stereocenter-generating iso-Nazarov cyclization through the synergy between the helicity of a pentadienyl cation intermediate and the control in the conformation of the allyl group, both elements defined upon alkoxy migration. The high barriers to conformational scrambling relative to those corresponding to chemical steps ensure the robustness of the chirality transfer mechanism and result in an unusual importance of conformational changes in reactivity that seems to be common in gold-catalyzed transformations.
TL;DR: Novel intermolecular and intramolecular generations of ortho-quinone methides and their formal [4+2]-cycloaddition reactions with olefins catalyzed by PtCl4 and AuCl3 under mild conditions and a mechanism accounting for its catalytic cycle is proposed and discussed.
TL;DR: Gold-catalysed generation of diol equivalents from epoxides and their intramolecular reaction with C≡C bonds to generate bicyclic ketals is presented in this paper.
TL;DR: In this article, the catalytic properties of the Pd-II-assisted reaction were evaluated in Suzuki-Miyaura cross-coupling reactions, using supercritical carbon dioxide (scCO 2 ) as a green solvent.
Abstract: The [2+3]cycloaddition of nitriles (RCN) with 2,2-dimethyl-3,4-dihydro-2H-pyrrole 1-oxide, in the presence of palladium dichloride (PdCl 2 ) gives the corresponding 2,3-dihydro[1.2.4]oxadiazole (Δ 4 -1,2,4-oxadiazoline) palladium(II) complexes 1―4 in good yields. However, the Pd(II)-assisted reaction of pentafluorobenzonitrile with the same pyrroline N-oxide gives a mixture of oxadiazoline 5, ketoimine 6 and pyrrolylbenzamide-ketoimine 7 Pd(II) complexes, which affords upon heating in refluxing acetone the unprecedented fused tricyclic ketoimine complex 8 as the exclusive product. Under heating, compounds 5 and 7 transform to 6, the latter undergoing intramolecular cyclization by nucleophilic attack of the amino moiety to the ortho carbon of the pentafluorophenyl ring leading ultimately to 8. The compounds were characterized by IR, 1 H and 13 C NMR, ESI + -MS, elemental analyses and, in the cases of 3, 6, 7 and 8, also by X-ray diffraction analyses. The catalytic properties of the Pd complexes were evaluated in Suzuki―Miyaura cross-coupling reactions, using supercritical carbon dioxide (scCO 2 ) as a green solvent. Cross-couplings of aryl halides with phenylboronic acid give the desired biaryl products in quantitative yields, in a short reaction time, for substrate-to-catalyst molar ratios as high as 4.0·10 4 .
TL;DR: Phenyliodine(III) bis(trifluoroacetate) (PIFA) can effect the intramolecular oxidative coupling of substituted 4-hydroxyphenyl-N-phenylbenzamides and constitutes an efficient method for the synthesis of spirooxindoles.
Abstract: Phenyliodine(III) bis(trifluoroacetate) (PIFA) can effect the intramolecular oxidative coupling of substituted 4-hydroxyphenyl-N-phenylbenzamides. The transformations could be realized in a catalytic manner by using iodobenzene as catalyst and m-chloroperoxybenzoic acid or urea·H 2 O 2 as terminal oxidant. This reaction constitutes an efficient method for the synthesis of spirooxindoles.
TL;DR: A novel protocol for the assembly of polysubstituted pyrroles has been developed through the acid-catalyzed, sequential three-component reaction of primary aliphatic amines, alkynoates and 1,2-diaza-1,3-dienes.
Abstract: A novel protocol for the assembly of polysubstituted pyrroles has been developed through the acid-catalyzed, sequential three-component reaction of primary aliphatic amines, alkynoates and 1,2-diaza-1,3-dienes (DDs). This methodology proceeds with complete chemo-/regioselectivity involving first formation of an enamino ester intermediate, in situ Michael addition with azo-ene compounds and subsequent intramolecular ring closure.
TL;DR: The asymmetric total synthesis of (-)-saframycin A, a natural antitumor product of the tetrahydroisoquinoline antitUMor antibiotics family, has been accomplished by employing L-tyrosine as the starting chiral building block in 24 steps for the longest linear sequence in an overall yield of 9.7%.
Abstract: The asymmetric total synthesis of (−)-saframycin A, a natural antitumor product of the tetrahydroisoquinoline antitumor antibiotics family, has been accomplished by employing l-tyrosine as the starting chiral building block in 24 steps for the longest linear sequence in an overall yield of 9.7%. The key steps in the synthesis involve stereoselective intermolecular and intramolecular Pictet–Spengler reactions, which induced the correct stereochemistry at C-1 and C-11, respectively. The selective protection–deprotection protocol of an amino group in the two-step transformation from intermediate 10 to 12 and a hydroxyl group in the first two steps resulted in both high selectivity and efficiency of the synthetic route.
TL;DR: In this paper, the oxidation of o-alkynylarene carbaldehydes into tricarbonyl compounds by an iodine/water system is described, where the reaction takes place via isochromenol intermediates formed by intramolecular assistance of the formyl group.
TL;DR: In this article, an enantioselective synthesis of bicyclic cyclopentenones is described, which is based on an iridium-catalyzed allylic substitution and an intramolecular diastere-selective Pauson-Khand reaction.
Abstract: Enantioselective syntheses of bicyclic cyclopentenones are described. Key steps are an iridium-catalyzed allylic substitution and an intramolecular diastereoselective Pauson–Khand reaction. The diastereoselectivity of the Pauson–Khand reaction was found to be crucially dependent on the unit connecting the propargylic and the olefinic parts of the precursor. Very high degrees of diastereoselection were obtained with an NBoc unit as connector. This methodology has been illustrated by application within an enantioselective formal total synthesis of (−)--kainic acid.
TL;DR: Three different series of experiments were undertaken to test the hypothesis that during irradiation of phosphonium-iodonium ylides an electrophilic carbene is generated and in the case of electron-rich substituents at the triple bond a domination of a 1,3-dipolar cycloaddition of the intermediate with the triple Bond to yield furans.
Abstract: We describe three different series of experiments which were undertaken to test our hypothesis that during irradiation of phosphonium−iodonium ylides (1a, 1b) an electrophilic carbene is generated. By opposing the assumed intermediate to monosubstituted alkynes, we observed in the case of electron-rich substituents at the triple bond a domination of a 1,3-dipolar cycloaddition of the intermediate with the triple bond to yield furans. In the case of electron poorer substituents, the formation of phosphinolines prevails. A second series of experiments was carried out with mixed ylides in which one phenyl ring at the triarylphosphonium group was replaced by a thienyl group. In this case, we observe only an intramolecular reaction with the thienyl ring to yield the phosphinolines 21−23. In a third test, we replaced in the mixed ylides 1a, 1b the COR group by a CN substituent. This modification leads to phosphinolines only and avoids a 1,3-dipolar cycloaddition.
TL;DR: Pyridine-N-oxide-borane intramolecular complexes having an aza-stilbene π-framework were synthesized by the palladium-catalyzed reaction of 2-bromopyridine -N-oxides with alkynyltriarylborates.