Showing papers on "Annulation published in 2013"
TL;DR: The objective of the review is to present the catalytic successes for C-H bond transformations in water, discovered mainly during the last six years and involving mostly palladium and ruthenium catalysts, often with the help of a carboxylate partner for the initial key C- H bond deprotonation.
Abstract: The metal-catalysed successive activation and functionalisation of sp2 C–H bonds is the at heart of synthetic innovations for the development of C–C bond cross-coupling processes. Against expectation catalytic C–H bond transformations can be performed in water as an available, renewable, safe solvent but most importantly as a partner improving the catalyst activity. The objective of the review is to present the catalytic successes for C–H bond transformations in water, discovered mainly during the last six years and involving mostly palladium and ruthenium catalysts, often with the help of a carboxylate partner for the initial key C–H bond deprotonation. Water is beneficial for the direct catalytic arylation with (hetero)aryl halides of functional arene ortho C–H bonds with pyridine, pyrazole, oxazoline, imine, urea, amide… directing groups leading to functional biaryl derivatives, polyheterocycles and polydentate ligands. Metal-catalysed activation of the sp2 C–H bond in water also allows the cross-coupling reaction of two different C–H bonds in the presence of an oxidant and regioselective alkenylations of arenes, heterocycles and functional alkenes are now controlled. Annulation reactions via insertion of alkynes into both activated C–H and heteroatom–hydrogen bonds in water constitute new routes to heterocycles.
474 citations
TL;DR: This intermolecular annulation involving tandem C-H activation, cyclization, and condensation steps proceeds under mild conditions, obviates the need for oxidants, releases N2 and H2O as the byproducts, and displays a broad substituent scope.
Abstract: Multisubstituted isoquinoline and pyridine N-oxides have been prepared by Rh(III)-catalyzed cyclization of oximes and diazo compounds via aryl and vinylic C–H activation. This intermolecular annulation involving tandem C–H activation, cyclization, and condensation steps proceeds under mild conditions, obviates the need for oxidants, releases N2 and H2O as the byproducts, and displays a broad substituent scope.
383 citations
TL;DR: The synthesis of pyrroloindolines via a catalytic enantioselective formal [3+2] cycloaddition of C(3)-substituted indoles is reported, with good yields and with high levels of enantioinduction.
Abstract: Herein we report the synthesis of pyrroloindolines via a catalytic enantioselective formal [3+2] cycloaddition of C(3)-substituted indoles. This methodology utilizes 4-aryl-1-sulfonyl-1,2,3-triazoles as carbenoid precursors and the rhodium(II)-tetracarboxylate catalyst Rh2(S-PTAD)4. A variety of aryl-substituted pyrroloindolines were prepared in good yields and with high levels of enantioinduction.
312 citations
249 citations
TL;DR: A novel and efficient Rh/O2 catalytic system has been developed and shown to catalyze highly efficient oxidative C-H activation/annulation reactions, producing a broad range of isoquinolinium salts with high turnover numbers.
Abstract: A novel and efficient Rh/O2 catalytic system has been developed and shown to catalyze highly efficient oxidative C-H activation/annulation reactions, producing a broad range of isoquinolinium salts with high turnover numbers (up to 740). Mechanistic studies provided strong evidence of facile oxidation of Rh(I) to Rh(III) by molecular oxygen facilitated by acid.
246 citations
TL;DR: High π-extended BBTNDT afforded very high mobility in its vapor-deposited organic field-effect transistors (OFETs), which is among the highest for unsubstituted acene- or thienoacene-based organic semiconductors in this class.
Abstract: We describe a new synthetic route to the [1]benzothieno[3,2-b][1]benzothiophene (BTBT) substructure featuring two consecutive thiophene-annulation reactions from o-ethynyl-thioanisole substrates and arylsulfenyl chloride reagents that can be easily derived from arylthiols. The method is particularly suitable for the synthesis of unsymmetrical derivatives, e.g., [1]benzothieno[3,2-b]naphtho[2,3-b]thiophene, [1]benzothieno[3,2-b]anthra[2,3-b]thiophene, and naphtho[3,2-b]thieno[3,2-b]anthra[2,3-b]thiophene, a selenium-containing derivative, [1]benzothieno[3,2-b][1]benzoselenophene. It also allows us to access largely π-extended derivatives with two BTBT substructures, e.g., bis[1]benzothieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene and bis[1]benzothieno[2,3-d:2′,3′-d′]naphtho[2,3-b:6,7-b′]dithiophene (BBTNDT). It should be emphasized that these new BTBT derivatives are otherwise difficult to be synthesized. In addition, since various substrates and reagents, o-ethynyl-thioanisoles and arylthiols, respec...
237 citations
TL;DR: The first general protocol to synthesize unprotected indoles through directed C–H annulation between arenes and alkynes by using a triazene as the DG is reported.
Abstract: The first general protocol for the synthesis of unprotected indoles via the title reaction is presented.
208 citations
TL;DR: The synthesis of highly functionalized pyrroles has been achieved by reaction of rhodium-stabilized imino-carbenes with furans, which features an initial [3+2] annulation to form bicyclic hemiaminals, followed by ring opening to generate trisubstituted p Pyrroles.
Abstract: The synthesis of highly functionalized pyrroles has been achieved by reaction of rhodium-stabilized imino-carbenes with furans. The reaction features an initial [3+2] annulation to form bicyclic hemiaminals, followed by ring opening to generate trisubstituted pyrroles.
202 citations
TL;DR: An efficient method to synthesize multiply substituted quinolines from three components, that is, diaryliodoniums 1, alkynes 2, and nitriles 3, is reported, which is regioselective, step economic, flexible with regard to functional groups, and is potentially applicable to complex molecules.
Abstract: A regioselective synthesis of a variety of substituted quinolines is developed using a Cu(II)-catalyzed three-component [2 + 2 + 2] cyclocondensation of diaryliodonium ions, nitriles, and alkynes, whereat the aryl group of the diaryliodonium serves as a C2 building block.
195 citations
TL;DR: Various spirocyclic molecules bearing an all-carbon quaternary stereocenter could be obtained by this novel method with good yields and excellent regioselectivity, and the current process tolerates a variety of synthetically important functional groups.
Abstract: Intermolecular annulation reactions of 1-aryl-2-naphthols with internal alkynes proceed efficiently in the presence of a Ru catalyst and a Cu oxidant to generate spirocyclic compounds by sequential cleavage of the C(sp2)-H bond, migratory insertion of the alkyne, and dearomatization of the naphthyl ring. Various spirocyclic molecules bearing an all-carbon quaternary stereocenter could be obtained by this novel method with good yields and excellent regioselectivity, and the current process tolerates a variety of synthetically important functional groups.
190 citations
TL;DR: The key step is an unprecedented catalytic asymmetric [3+2] annulation of isatin-derived MBH adducts, containing a tetrasubstituted alkene moiety, with isatins.
Abstract: All in a sequence: An organocatalyzed Morita-Baylis-Hillman (MBH)/bromination/[3+2] annulation sequence for highly stereoselective syntheses of bis(spirooxindole)s featuring adjacent spiro-stereocenters is described. The key step is an unprecedented catalytic asymmetric [3+2] annulation of isatin-derived MBH adducts, containing a tetrasubstituted alkene moiety, with isatins.
TL;DR: Revitalization by oxygen: A rhodium(III)-catalyzed oxidative CH/NH activation/annulation sequence provided access to a variety of substituted 1,2-benzothiazine derivatives from readily available NH-sulfoximines and alkynes.
Abstract: Revitalization by oxygen: A rhodium(III)-catalyzed oxidative CH/NH activation/annulation sequence provided access to a variety of substituted 1,2-benzothiazine derivatives from readily available NH-sulfoximines and alkynes (see scheme; Cp*=C5 Me5 ). The oxidation system consisted of molecular oxygen in combination with a catalytic amount of Fe(OAc)2 .
TL;DR: Benzophosphole construction was achieved through the Ag(I) -mediated dehydrogenative annulation of phenylphosphine oxides with internal alkynes in a process involving C�C and CP bond formation with perfect regioselectivity.
Abstract: Benzophosphole construction was achieved through the Ag(I) -mediated dehydrogenative annulation of phenylphosphine oxides with internal alkynes in a process involving CC and CP bond formation. A wide range of asymmetrical phenylacetylenes could be employed and the reactions proceeded with perfect regioselectivity. Moreover, the annulation could be conducted even at room temperature when a Mn(III) promoter was used in place of Ag(I) .
TL;DR: 2,3-Disubstituted benzo[b]furans are prepared in one step from commercially available phenols and readily accessible unactivated internal alkynes to create a Pd-catalyzed oxidative annulation that has a broad substrate scope and allows access to a wide range of benzo-b-furans.
Abstract: 2,3-Disubstituted benzo[b]furans are prepared in one step from commercially available phenols and readily accessible unactivated internal alkynes (see scheme). This Pd-catalyzed oxidative annulation has a broad substrate scope and allows access to a wide range of benzo[b]furans.
TL;DR: A novel synthesis of azepinone derivatives by using a Rh-catalyzed intramolecular annulation reaction of N-substituted benzamides and α,β-unsaturated aldehydes and ketones is developed.
Abstract: A novel synthesis of azepinone derivatives by using a Rh-catalyzed intramolecular annulation reaction of N-substituted benzamides and α,β-unsaturated aldehydes and ketones is developed.
TL;DR: Versatile nickel catalysts enabled the step-economical synthesis of decorated indoles through alkyne annulations with anilines bearing removable directing groups with excellent selectivities.
TL;DR: The Rh(III) -catalyzed reaction of O-methyl α,β-unsaturated oximes with aldehydes and N-tosyl imines affords secondary alcohol and amine intermediates, respectively.
Abstract: Ring in the new: a new annulation for the efficient synthesis of substituted furans and pyrroles is reported. The Rh(III) -catalyzed reaction of O-methyl α,β-unsaturated oximes with aldehydes and N-tosyl imines affords secondary alcohol and amine intermediates, respectively. Cyclization and aromatization occurs under the reaction conditions to provide access to biologically relevant furans and pyrroles in good yields. Cp*=C(5)Me(5), DCE=1,2-dichloroethane, THF=tetrahydrofuran.
TL;DR: An efficient and mechanistically interesting method for the synthesis of highly substituted isoquinolines by a Rh(III)-catalyzed hydrazone directed ortho C-H bond activation and annulation without an external oxidant is described.
TL;DR: An efficient Cu-catalyzed synthesis of quinazolines via the C-N bond formation reactions between N-H bonds of amidines and C(sp(3))-H bonds adjacent to sulfur or nitrogen atoms in the commonly used solvents, followed by intramolecular C-C bond formation reaction was developed for the first time.
TL;DR: An efficient and regioselective ruthenium-catalyzed oxidative annulation of enamides with alkynes via the cleavage of C(sp(2))-H/N-H bonds is reported.
TL;DR: This work demonstrates the divergent C-H functionalization of unsymmetrical 2-aryl cyclic 1,3-dicarbonyl compounds that contain two distinct, nonadjacent sites for initial C- H functionalization, where product selectivity is achieved through catalyst control.
Abstract: Achieving site-selective, switchable C–H functionalizations of substrates that contain several different types of reactive C–H bonds is an attractive objective to enable the generation of different products from the same starting materials. Herein, we demonstrate the divergent C–H functionalization of unsymmetrical 2-aryl cyclic 1,3-dicarbonyl compounds that contain two distinct, nonadjacent sites for initial C–H functionalization, where product selectivity is achieved through catalyst control. By use of a palladium–N-heterocyclic carbene complex as the precatalyst, these substrates undergo oxidative annulation with alkynes to provide spiroindenes exclusively. In contrast, a ruthenium-based catalyst system gives benzopyrans as the major products. Examples of divergent, oxidative C–H alkenylations of the same substrates are also provided.
TL;DR: The mechanism study suggests that (S)-Trip plays multiple roles in assembling the reactants and controlling the stereoselectivity, and shows great efficiency in establishing dense multiple chiral centers including quaternary carbons of variable bridged ring systems.
Abstract: An asymmetric cascade annulation between 2-hydroxystyrenes and 2-alkynylbenaldehyes or 1-(2-alkynylphenyl)ketones has been established with good to excellent enantioselectivities (up to >99.5% ee), on the basis of an enantioselective oxa-Diels–Alder cycloaddition of in situ generated metallo-isochromenylium intermediates, by cooperative binary catalysis of Pd(OAc)2 and (S)-Trip. The developed methodology is workable for a broad spectrum of substrates and shows great efficiency in establishing dense multiple chiral centers including quaternary carbons of variable bridged ring systems. The mechanism study suggests that (S)-Trip plays multiple roles in assembling the reactants and controlling the stereoselectivity.
TL;DR: Mechanistic studies disclosed a new strategy on annulations of alkynes with phenols through reversible electrophilic carbocupration of phenol followed by alkyne insertion and cyclization.
Abstract: The first example of copper-mediated oxidative annulation of phenols and unactivated internal alkynes to afford benzofuran derivatives was reported. Various phenols and unactivated internal alkynes were successfully employed. Mechanistic studies disclosed a new strategy on annulations of alkynes with phenols through reversible electrophilic carbocupration of phenol followed by alkyne insertion and cyclization.
TL;DR: Alkyne tethered benzamides undergo rhodium(III)-catalyzed intramolecular annulations to give tricyclic isoquinoline derivatives in good yields.
Abstract: Alkyne tethered benzamides undergo rhodium(III)-catalyzed intramolecular annulations to give tricyclic isoquinoline derivatives in good yields. DFT calculations suggest that the reaction mechanism involves a migratory insertion of the alkyne into the rhodium–nitrogen bond of the rhodacycle intermediate that results from the initial C–H activation. This contrasts with the pathway proposed for intermolecular cases, which considers an insertion into the rhodium–carbon instead of the rhodium–nitrogen bond. The annulation is also effective with acrylamides; and, while anilides fail to participate in the process, naphthylamides do undergo the intramolecular annulation, albeit the chemoselectivity is different than for the intermolecular reactions.
TL;DR: Under redox-neutral conditions, rhodium(III)-catalyzed C-H annulation of N-tert-butyl-α-arylnitrones with internal alkynes has been realized for the synthesis of indenones under mild conditions and proceeded in moderate to high yields and with good functional group tolerance.
TL;DR: Racemization required: Rhodium(I)-catalyzed C-H activation directed by unprotected ketimines initiates selective [3+2] cycloaddition with allenes, providing access to highly substituted indenylamines.
Abstract: Keywords: allenes ; asymmetric catalysis ; CH activation ; DYKAT ; rhodium Reference EPFL-ARTICLE-190184doi:10.1002/anie.201304919View record in Web of Science Record created on 2013-11-04, modified on 2017-05-12
TL;DR: The asymmetric annulation of a range of α,β-unsaturated acyl ammonium intermediates, formed from isothiourea HBTM 2.1 and anhydrides with either 1,3-dicarbonyls, β-ketoesters or azaaryl ketones gives either functionalised esters (upon ring opening), dihydropyranones or dihydrophyridones in good yields and high enantioselectivity (up to 97% ee) as mentioned in this paper.
Abstract: The asymmetric annulation of a range of α,β-unsaturated acyl ammonium intermediates, formed from isothiourea HBTM 2.1 and anhydrides with either 1,3-dicarbonyls, β-ketoesters or azaaryl ketones gives either functionalised esters (upon ring opening), dihydropyranones or dihydropyridones in good yields (up to 93%) and high enantioselectivity (up to 97% ee).
TL;DR: An efficient one-pot synthetic protocol has been proposed for the synthesis of luntonin F from easily available starting materials usingiodination, Kornblum oxidation, and annulation through a rational logical design.
TL;DR: The first phosphine-catalyzed [4 + 2] annulation of γ-substituted allenoates with 2-arylidene-1H-indenes-1,3(2H)-diones is disclosed, offering a powerful approach to the construction of highly substituted spiro[4.5]dec-6-ene skeletons in excellent yields, and with complete regioselectivity and high diastereoselectivities.