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PubMed Journals Articles About "Catalyzed Selective Allylation Hydroamination Cascade Synthesis Dihydroisoquinolines" RSS

08:42 EST 22nd January 2020 | BioPortfolio

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Showing "Catalyzed Selective Allylation Hydroamination Cascade Synthesis Dihydroisoquinolines" PubMed Articles 1–25 of 9,800+

Cp*Co(III)-Catalyzed γ-Selective C-H Allylation/Hydroamination Cascade for the Synthesis of Dihydroisoquinolines.

A Cp*Co(III)-catalyzed γ-selective C-H allylation/hydroamination cascade toward the synthesis of 3,4-dihydroisoquinolines (DHIQs) has been successfully developed, starting from NH ketimines and allyl carbonates. Notably, highly efficient and γ-selective C-H allylations were accomplished using γ-substituted allyl reagents, thus overcoming the issues of poor α/γ selectivity and low reactivity of previous transition metal-catalyzed C-H allylations. The stereochemistry of allyl carbonates was a crucial fac...


Asymmetric Palladium-Catalyzed C‒H Functionalization Cascade for Synthesis of Chiral 3,4-Dihydroisoquinolones.

A palladium-catalyzed C‒H functionalization/intramolecular asymmetric allylation cascade of N-sulfonyl benzamides with 1,3-dienes has been developed. In the presence of a chiral pyridine-oxazoline ligand, this protocol enables the synthesis of chiral 3,4-dihydroisoquinolones in yields of up to 83% with enantioselectivities of up to 96%, using environmentally friendly air as the terminal oxidant.

Oxazolinyl-Assisted Ru(II)-Catalyzed C-H Allylation with Allyl Alcohols and Synthesis of 4-methyleneisochroman-1-ones.

We report herein a ruthenium-catalyzed, oxazoline-directed strategy for C-H allylation of aryl oxazolines using allylic alcohols as the coupling partner. The present transformation unravels the unusual reactivity of allylic alcohols in the synthesis of 4-methyleneisochroman-1-ones and C-H allylated products. A complete switch in the product selectivity was observed with substrate control and tuning the reaction conditions. The approach employs allyl alcohols as an efficient alternative to preactivated allyl...


Asymmetric Total Syntheses of (-)-Angustureine and (-)-Cuspareine via Rhodium-Catalyzed Hydroamination.

Concise syntheses of the Hancock alkaloids (-)-angustureine and (-)-cuspareine are presented, applying and refining a recently developed rhodium-catalyzed hydroamination for the stereoselective construction of the chiral secondary amine. Furthermore, the syntheses include an allene synthesis via boron-magnesium exchange as well as the construction of the tetrahydroquinoline motive via a hydroboration/Suzuki-Miyaura coupling sequence.

Bi(III)-Catalyzed Enantioselective Allylation Reactions of Ketimines.

Chiral homoallylic amines not only are found in pharmaceutically relevant compounds but also serve as versatile building blocks for chemical synthesis. However, catalytic allylation of ketimines with allylboronates, an attractive approach to synthesize chiral homoallylic amine scaffolds remain scarce. Herein, we develop a highly enantioselective allylation of isatin-derived ketimines with boron allylation reagents catalyzed by a Bi(OAc)-chiral phosphoric acid catalyst system. The reactions are remarkably ef...

Manganese-Catalyzed Aromatic C-H Allylation of Ketones.

Manganese-catalyzed aromatic C-H allylation of ketones is reported. The reaction proceeded in a monoselective allylation manner to provide various C-H allylated ketones in high yields. With challenging allylic electrophiles bearing substituents at the α-, β-, or γ-position, excellent S2' regioselectivity was achieved under mild conditions (rt to 35 °C). Mechanistic studies revealed a possible turnover-limiting C-H bond cleavage step affording a five-membered manganacycle followed by reaction with allyl...

Synthesis of 4,4-Difluoroalkenes by Coupling of α-Substituted α,α-Difluoromethyl Halides with Allyl Sulfones under Photoredox Catalyzed Conditions.

Photoredox-catalyzed allylation of α- gem-difluorinated organohalides with allyl sulfones proceeded smoothly under visible light irradiation to give 4,4-difluoroalkenes in good yields. In the presence of catalytic Ru(bpy)Cl, Hantzsch ester, and diisopropylethylamine, the reaction was complete within 2 h. Using the same methodology, three-component cascade reactions to give 6,6-difluoroalkenes were carried out successfully.

Ring-Opening -C-H Allylation of Benzoic Acids with Vinylcyclopropanes: Merging Catalytic C-H and C-C Activation Concepts.

A Ru-catalyzed selective and atom-economic -C-H allylation of aromatic acids with vinylcyclopropanes is reported. The reaction proceeds with selective cleavage of both a C-H and a C-C bond. A wide range of allylarenes were synthesized in high yields and stereoselectivities. The vinylcyclopropane substrates can optionally be generated in situ from a diazo compound and 1,3-butadiene. Concise syntheses of isocoumarin and 3,4-dihydroisocoumarin derivatives underline the synthetic utility of the reaction.

Visible-Light-Induced Copper-Catalyzed Intermolecular Markovnikov Hydroamination of Alkenes.

A visible-light-induced copper-catalyzed intermolecular hydroamination of alkenes using commercially accessible primary and secondary amines has been established. This effective method exhibits good tolerance of a broad range of functional groups and provides a facile access to an array of valuable amines with Markovnikov regioselectivity. The process can be positively expected to be used in bioactive amines, and it may provide new potential in the discovery of copper-catalyzed hydrofunctionalization reacti...

Development of a Strategy for Linear-Selective Cu-Catalyzed Reductive Coupling of Ketones and Allenes for the Synthesis of Chiral γ-Hydroxyaldehyde Equivalents.

We report the development of a stereoselective method for the allylation of ketones utilizing -substituted allyl equivalents generated from a chiral allenamide. By choice of the appropriate ligand for the Cu-catalyst, high linear selectivity can be obtained with good diastereocontrol. This methodology allows access to chiral γ-hydroxyaldehyde equivalents that were applied in the synthesis of chiral γ-lactones and 2,5-disubstitued tetrahydrofurans.

Copper-Catalyzed Cascade Cyclization of Arylsulfonylhydrazones Derived from -Alkynyl Arylketones: Regioselective Synthesis of Functionalized Cinnolines.

A novel copper-catalyzed cascade reaction of arylsulfonylhydrazones derived from -alkynyl arylketones was accomplished. This reaction provides concise access to diversified cinnolines in good yields. The mechanistic investigations have disclosed involvement of the key alkynyl amination, 1,4-aryl migration, desulfonylation, and diazo radical cyclization cascade in the transformation.

Cascade π-Extended Decarboxylative Annulation Involving Cyclic Diaryliodonium Salts: Site-Selective Synthesis of Phenanthridines and Benzocarbazoles via a Traceless Directing Group Strategy.

A novel cascade π-extended decarboxylative annulation (PEDA) involved with cyclic diaryliodonium salts is described. Via fine-tuning of the reaction conditions, the Pd(II)-catalyzed site-selective N1/C2 or C2/C3 annulation of commercially available indole-2-carboxylic acids can be achieved, affording valuable phenanthridines or benzocarbazoles, respectively. The key strategy is the carboxylic acid functionality being employed as both a traceless directing group for the C-N or C-C coupling and a reactive g...

Imidate as the Intact Directing Group for the Cobalt-Catalyzed C-H Allylation.

Cobalt-catalyzed C-H allylation reactions of NH-free benzimidates using vinylcyclopropanes or allyl carbonate are reported. The reactive and relatively unstable imidate groups remain intact during the C-H allylations to afford functionalized imidates without dealcoholizations. The thus obtained allylated imidate was subsequently converted into other heterocyclic structures through a following C-H functionalization reaction, demonstrating the synthetic utility of this method.

Palladium-Catalyzed Cascade Reactions of 2-(Cyanomethoxy)chalcones with Arylboronic Acids: Selective Synthesis of Emissive Benzofuro2,3-pyridines.

The Pd(II)-catalyzed cascade reactions of 2-(cyanomethoxy)chalcones with arylboronic acids were demonstrated, allowing the rapid construction of benzofuro[2,3-]pyridine skeletons with excellent selectivity. These transformations involve the domino-style formation of C-C/C-C/C-N bonds through nitrile carbopalladation, intramolecular Michael addition, cyclization, and aromatization. This chemistry allows for the reactions of 2-(cyanomethoxy)chalcones with thiophen-3-ylboronic acid, providing 3-aryl-1-(thiophe...

Direct Access to 9-Chloro-1-benzofuro3,4-azepin-1-ones via Palladium(II)-Catalyzed Intramolecular -Oxypalladation/Olefin Insertion/sp-C-H Bond Activation Cascade.

An efficient Pd(II)-catalyzed cascade approach was established for the synthesis of 9-chloro-1-benzo[]furo[3,4-]azepin-1-ones starting from -propargyl arylamines having a pendant α,β-unsaturated ester scaffold. The mechanism of this sequential process involved intramolecular -oxypalladation followed by olefin insertion and sp-C-Cl bond formation reactions. This high atom- and step-economical cascade sequence generated two heterocycle rings and three new bonds in a single synthetic operation.

Synthesis of the Madangamine Alkaloid Core by a C-C Bond Activation Cascade.

The diazatricyclic core of the madangamine alkaloids was synthesized from a densely functionalized cyclohexane derivative. An alkene and two cyanoformamide groups are used to form two new rings and a new quaternary stereocenter in a cascade reaction, which involves two Pd-catalyzed C-C bond activation steps. The synthesis of the cascade precursor involves an intramolecular Staudinger reaction of a vicinal diester that gives a [3.2.1]azabicyclooctane derivative, allowing the regioselective introduction of a ...

A Pd-catalyzed asymmetric allylic substitution cascade via an asymmetric desymmetrization for the synthesis of bicyclic dihydrofurans.

A Pd-catalyzed asymmetric allylic substitution cascade of allylic meso-dicarbonates with 3-oxo-nitriles has been developed for the synthesis of chiral bicyclic dihydrofurans bearing two vicinal carbon stereocenters. The reaction proceeds via an asymmetric desymmetrization process with the desired products being obtained in high yields and with up to 97% ee. The reaction was performed on a gram-scale and the corresponding bicyclic dihydrofurans could undergo several transformations. The methodology provides ...

Total Synthesis of Diocollettines A via an Acid-Promoted Oxa-Michael-Aldol-Acetalization Cascade.

A diastereo- and enantioselective total synthesis of diocollettines A with an unusual oxygen-containing tricyclic ring system has been achieved in 63% overall yield from commercially available 3-phenylpropanal via four steps. The key feature of the present synthesis is an exclusively diastereoselective cascade sequence composed of a -selective oxa-Michael addition of 1,3-dihydroxyacetone to a 2,3-dihydropyrylium ion intermediate, intramolecular aldol-type reaction, and intramolecular acetalization.

Palladium(II)-Catalyzed Reductive Cyclization of -Tosyl-Tethered 1,7-Enynes: Enantioselective Synthesis of 1,2,3,4-Tetrahydroquinolines.

A novel Pd(II)-catalyzed reductive asymmetric cyclization of -tosyl-tethered 1,7-enynes using ethanol as a hydrogen source is reported. This reaction provides facile ways for the synthesis of two types of 1,2,3,4-tetrahydroquinolines possessing a chiral quaternary carbon center in high yields with excellent enantioselectivities. The obtained products can also be converted to other chiral functionalized tetrahydroquinolines efficiently. The procedure involves a palladium-catalyzed intramolecular hydropallada...

Manganese-catalyzed cascade annulations of alkyne-tethered N-alkoxyamides: synthesis of polycyclic isoquinolin-1(2H)-ones.

A strategy for the synthesis of isoxazolidine/1,2-oxazinane-fused isoquinolin-1(2H)-ones from alkyne-tethered N-alkoxyamides is described, in which cheap Mn(acac)2 is used as a catalyst to facilitate a radical cascade annulation. The method features mild conditions, additive-free reaction and broad substrate scope. It is the first example via manganese/air catalytic systems to construct isoquinolin-1(2H)-one heterocycles.

Labelling and Natural Posttranslational Modification of Peptides and Proteins via Chemoselective Pd-Catalyzed Prenylation of Cysteine.

The prenylation of peptides and proteins is an important posttranslational modification observed in vivo. We report that the Pd-catalyzed Tsuji-Trost-allylation with a Pd/BIPHEPHOS catalyst system allows the allylation of Cys-containing peptides and proteins with complete chemoselectivity and high n/i regioselectivity. In contrast to recently established methods, which use non-native connections, the Pd-catalyzed prenylation produces the natural n-prenylthioether bond. In addition, a variety of biophysical ...

Modular Synthesis of Polycyclic Alkaloid Scaffolds via an Enantioselective Dearomative Cascade.

The polycyclic core of the akuammiline alkaloids can be synthesized from simple tryptamine and tryptophol derivatives via a Ag(I)-catalyzed enantioselective dearomative cyclization cascade sequence. The complex tetracyclic scaffolds are prepared via a rapid, versatile, three-step modular synthesis from simple commercially available indole derivatives in high yields and enantiomeric excess (up to 99% yield and >99% ).

Gold(I)-Catalyzed Aromatization: Expeditious Synthesis of Polyfunctionalized Naphthalenes.

A gold-catalyzed 6-endo-dig carbocyclization of alkyne with the pendent diazo group is reported. It provides an expeditious approach for the synthesis of multi-functionalized naphthalene derivatives under mild conditions. Mechanistic studies suggest that a vinyl gold carbene is generated as the key intermediate in this cascade transformation that smoothly delivers naphthalene products through an unprecedented stepwise aromatization or an intermolecular aromatic substitution process. The unique endocyclic vi...

Selective Defluoroallylation of Trifluoromethylarenes.

We report a fluoride-initiated coupling reaction between trifluoromethylarenes and allylsilanes to access allylated α,α-difluorobenzylic compounds. This method's utility is demonstrated through a 30 mmol scale reaction, a sequential allylation/derivatization protocol and multiple examples of site-selective trifluoromethylarene allylation. Initial mechanistic studies suggest a base-induced single electron transfer pathway is responsible for the high efficiency and selectivity of this novel C-F substitution...

Copper-Catalyzed Cascade Cyclization Reaction of Enamines and Electron-Deficient Terminal Alkynes: Synthesis of Polysubstituted Pyrido1,2-indoles.

A novel copper-catalyzed cascade cyclization reaction between enamines and electron-deficient terminal alkynes has been developed. The reaction provides a new and efficient strategy for the construction of polysubstituted pyrido[1,2-]indoles by the formation of two rings, three C-C bonds, and one C-N bond in a single step from readily available acyclic starting materials.


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