RESUMO
An unusual spiroannulation/cycloisomerization cascade of 3-(2-ethynylaryl)-N-tosylaziridines with indoles enabled by cooperative gold/scandium catalysis is presented, which facilitates the synthesis of 5H-benzo[b]carbazoles in moderate to excellent yields. This protocol features a broad substrate scope and good functional-group compatibility. Additionally, the resulting 5H-benzo[b]carbazoles exhibit good fluorescence properties, demonstrating the synthetic practicality of this method. Moreover, control experiments were performed to illustrate the reaction mechanism.
RESUMO
A visible-light-induced defluorinative dichloromethylation of α-CF3 alkenes was developed with cheap and readily accessible chloroform simultaneously as a dichloromethylation reagent and reaction medium, leading to the facile preparation of new polyhalogenated scaffolds. Notably, the change from CHCl3 to CDCl3 offers a straightforward pathway for accessing the deuterated analogues with excellent degrees of D incorporation. Mechanistic studies suggested the reaction underwent a radical addition of the dichloromethyl radical with alkenes, followed by sequential single-electron transfer and defluorination. This protocol features mild conditions, easy operation, facile scalability, and high efficiency, allowing convenient access to dichloronated gem-difluoroalkenes.
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Reported herein is a visible-light-induced, catalyst-free intramolecular cyclization of 4-phenylsulfonyl-2,3,5,6-tetrachloropyridine, leading to rapid assembly of a series of unprecedented benzo[4,5]thieno[3,2-c]pyridine 5,5-dioxide scaffolds under mild conditions. The rational introduction of a perchloropyridin-4-yl module significantly facilitated this photoinduced process and offers a versatile platform for broad structural variation. Mechanistic studies revealed that a newly identified charge-transfer complex with carbonate is crucial to this photoinduced process.
RESUMO
Reported herein is a photoredox-catalyzed amination of o-hydroxyarylenaminones with tert-butyl ((perfluoropyridin-4-yl)oxy)carbamate, a versatile amidyl-radical precursor developed in our laboratory. This work establishes a new cascade pathway for the assembly of a range of 3-aminochromones under mild conditions. Downstream transformations of the obtained 3-aminochromones to construct diverse amino pyrimidines greatly broaden the applications of this photocatalyzed protocol.
Assuntos
Cromonas , Aminação , CatáliseRESUMO
A metal-free photosensitized protocol for regioselective diamination of alkene feedstocks over a single step was developed based on the rationally designed bifunctional diamination reagent, thus affording a range of differentially protected 1,2-diamines in moderate to high yields. Mechanistic studies reveal that the reaction is initiated with a triplet-triplet energy transfer between thioxanthone catalyst and diamination reagent, followed by fragmentation to simultaneously generate long-lived iminyl radical and transient amidyl radical. The excellent regioselectivity presumably stems from the large reactivity difference between two different N-centered radical species. This protocol is characterized by excellent regioselectivity, broad functional group tolerance, and mild reaction conditions, which would enrich the diversity and versatility of facilitate the diversity-oriented synthesis of 1,2-diamine-containing complex molecule scaffolds.
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An unprecedented photoredox-catalyzed phosphine-mediated deoxygenation of hexafluoroacetone hydrate was established to accomplish the hydroxylpolyfluoroalkylation of electron-deficient alkenes. A range of bis(trifluoromethyl)carbinols were facilely accessed by using readily available hexafluoroacetone hydrate, instead of toxic gaseous hexafluoroacetone. A range of electron-deficient alkenes are tolerated, giving the corresponding hydro-hydroxylpolyfluoroalkylated products in moderate to high yields. Remarkable features of this synthetic strategy include operational simplicity, mild reaction conditions, excellent regioselectivity, and broad functional group tolerance. The success of this strategy relies on the delicate utilization of aldehyde/ketone-gem-diol intrinsic equilibrium, which offers an innovated open-shell pathway for the assembly of synthetically challenging polyfluoroalkylated scaffolds.
Assuntos
Alcenos , Fluorocarbonos , Catálise , AcetonaRESUMO
A visible light-promoted radical relay of N-allylbromodifluoroacetamide with quinoxalin-2(1H)-ones was developed in which 5-exo-trig cyclization and C-C bond formation were involved. This protocol was performed under mild conditions to facilely offer a variety of hybrid molecules bearing both quinoxalin-2(1H)-one and 3,3-difluoro-γ-lactam motifs. These prepared novel skeletons would expand the accessible chemical space for structurally complex heterocycles with potential biological activities.
Assuntos
Luz , Quinoxalinas , Ciclização , Lactamas , Estrutura MolecularRESUMO
A novel phosphine-catalysed, one-pot domino approach for the annulation of 2-formylphenyl alkynoates with activated methylene compounds to construct various cyclopentene-fused dihydrocoumarins is reported. This developed strategy provides a facile and efficient approach for the synthesis of structurally complex coumarins from inexpensive and readily available alkynoates.
RESUMO
A visible-light-induced, catalyst-free radical cross-coupling cyclization of diselenides or disulfides with N-allylbromodifluoroacetamide has been developed. This developed protocol exhibits good functional group tolerance and affords a variety of 4-thio- and 4-seleno-substituted 3,3-difluoro-γ-lactams in moderate to good yields. Based on control experiments, a plausible radical-radical cross-coupling pathway is proposed.
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Chromanone is a privileged structure with a wide range of unique biological activities. A phosphine-promoted, three-component domino sequence of salicylaldehyde with but-3-yn-2-one was well designed for the construction of the chromanone skeleton under mild conditions. As a consequence, a series of novel chromanone analogues bearing an all-carbon quaternary center were facilely assembled from commercially available starting materials with moderate to good yields, which hold promising applications in pharmacological studies. Mechanistic experiments were conducted to confirm the proposed mechanism.
RESUMO
A photoinduced SET process enables the direct B-H bond activation of NHC-boranes. In contrast to common hydrogen atom transfer (HAT) strategies, this photoinduced reaction simply takes advantage of the beneficial redox potentials of NHC-boranes, thus obviating the need for extra radical initiators. The resulting NHC-boryl radical was used for the borylation of a wide range of α-trifluoromethylalkenes and alkenes with diverse electronic and structural features, providing facile access to highly functionalized borylated molecules. Labeling and photoquenching experiments provide insight into the mechanism of this photoinduced SET pathway.
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One-pot ring-opening/ring-closure process of combining methyleneindolinone with 3-aminooxindole has been developed in this work. Novel polycyclic spirooxindoles were efficiently assembled under mild conditions in high yields (up to 95 %) with moderate to good diastereoselectivities (up to >95:5â d.r.) through simple filtration.
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A general and straightforward protocol for di-/perfluoroalkylation of ortho-hydroxycinnamic esters via a photoredox-catalyzed cascade was developed to access a variety of 3-fluoroalkylated coumarins. This method was characterized by all-in-one synthetic design, simplified operation, mild reaction conditions, and broad substrate scope. Moreover, a sequential one-pot procedure starting from commercially available salicylaldehyde was also successfully realized to synthesize 3-fluoroalkylated coumarins.
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A palladium-catalyzed ring-opening oxo-formal [3 + 2]-cycloaddition reaction of novel donor-acceptor spirovinylcyclopropyl oxindole with 3-oxindole is described. The developed protocol provides facile access to oxo-bispirooxindole derivatives in good yields (up to 82% yield) with excellent diastereoselectivities (up to 20:1 dr).
RESUMO
A new strategy for the synthesis of functionalized tetrahydrofuran derivatives was developed via a phosphine-catalysed [3 + 2] cyclization reaction of aromatic aldehydes with 4-phenylbut-3-yn-2-one. This is the first example of intermolecular cyclization of ynones with benzaldehydes, which essentially benefited from the intramolecular hydrogen bonding. This new protocol features a broad substrate scope, mild reaction conditions, operational simplicity and easy scale-up.
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An efficient and diastereoselective decarboxylative oxa-1,3-dipolar cycloaddition between 3-oxindoles and diverse amino acids is developed to access novel oxazolidine-dispirooxindole skeletons bearing vicinal quaternary carbon centers. This protocol features operational simplicity, a broad substrate scope, and good to excellent chemical yields and diastereoselectivities. In particular, minimal solvent (1 mL/10 mmol) and chromatography-free purification render this synthetic process more efficient and environmentally benign in the context of green chemistry.
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A facile and enantioselective access to a functionalized octahydroacridine scaffold was developed via an organocatalytic domino sequence between cyclohexenone and 2- N-substituted benzaldehyde. High levels of yields (up to 99%) and enantioselectivities (up to 99:1 er) were readily achieved in this developed organocatalytic transformation, which holds promising applications in the construction of complex multicyclic systems for further pharmacological studies.
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A novel palladium-catalysed ring-opening [3 + 2]-annulation of spirovinylcyclopropyl oxindole with α,ß-unsaturated nitroalkenes is reported. A series of spirooxindole derivatives were synthesized in high yields and good to excellent diastereoselectivities. This developed protocol offers a new and efficient pathway for the assembly of spirooxindoles.
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Hydrogen-bonding organocatalysts L-pyroglutamic sulphonamides were readily synthesized for the first time by fully exploiting the potentials of L-pyroglutamic acid. The newly designed catalyst was successfully applied in catalyzing asymmetric Diels-Alder cyclization of methyleneindolinones with 2-vinyl-1H-indoles to efficiently assemble carbazolespirooxindoles in excellent stereoselectivity (up to 99% ee, >20:1 dr) and yields (up to 99%). Mechanistic studies disclosed that the well-designed hydrogen-bonding modes between L-pyroglutamic sulphonamide and substrates were crucial for stereocontrol in the cyclization.
RESUMO
Reductive dimerization of isatin and its derivatives can be regarded as a step-economical pathway to construct 3,3'-disubstituted bisoxindoles, which was unfortunately accompanied by severe direct reduction as well as low efficiency. A visible-light driven, photoredox-catalytic protocol was developed to readily furnish 3,3'-dihydroxy- (dl-, > 20:1 dr) and 3,3'-diamino-bisoxindoles (meso-, 3.5:1 to 5:1 dr) in moderate to good yields, successfully circumventing the common problem. Two vicinal quaternary carbon centers were effectively assembled under the irradiation of visible light.