Aryl Ketoximes Research Articles

Cucurbit[7]uril-Catalyzed Beckmann Rearrangement of Arylketoximes.

With the existence of cucurbit[7]uril (Q[7]), a supramolecular catalysis strategy for the Beckmann rearrangement of aryl ketoximes to N-substituted amides was successfully established. The cavity of Q[7] was found to be essential for substrate encapsulation and the rearrangement reaction through comparative experiments and studies on host-guest interactions. This supramolecular strategy provides an efficient route for the rearrangement reaction incorporating a carbonation intermediate.

Cobalt-catalyzed three-component assembly of aromatic oximes with substituted dienes and formaldehyde.

A cobalt-catalyzed three-component assembly of substituted aryl oximes with dienes and formaldehyde via C-H bond activation is described. This protocol affords highly regio- and chemoselective substituted homoallylic alcohols with moderate-to-excellent yields. The scope of this protocol has been extensively explored with various substituted aryl ketoximes and aldoximes. Butadiene and internally substituted dienes are also well compatible for this transformation. A plausible reaction mechanism is proposed to account for the present reaction and is supported by deuterium labeling studies.

Construction of Cyclic Nitrones Enabled by Photodriven and Gold-Catalyzed 1,3-Azaprotio Transfer of Allenyloximes.

A protocol was developed to construct five- to seven-membered cyclic nitrones through the gold-catalyzed 1,3-azaprotio transfer of allenyloximes under photoirradiation. The photoisomerization of oximes was suggested to convert the inert stereoisomer to a reactive one. This photodriven and gold-catalyzed ring formation could be further extended to the thermodynamically stable aryl ketoximes with an E-configuration, which previously displayed chemical inertness in the absence of light irradiation.

Copper-catalyzed [1,3]-nitrogen rearrangement of O-aryl ketoximes via oxidative addition of N-O bond in inverse electron flow.

The [1,3]-nitrogen rearrangement reactions of O-aryl ketoximes were promoted by N-heterocyclic carbene (NHC)-copper catalysts and BF3·OEt2 as an additive, affording ortho-aminophenol derivatives in good yields. The reaction of substrates with electron-withdrawing substituents on the phenol moiety are accelerated by adding silver salt and modifying the substituent at the nitrogen atom. Density functional theory calculations suggest that the rate-determining step of this reaction is the oxidative addition of the N-O bond of the substrate to the copper catalyst. The negative ρ values of the substituent at both the oxime carbon and phenoxy group indicate that the donation of electrons by the oxygen and nitrogen atoms accelerates the oxidative addition.

Directing-Group-Free Palladium-Catalyzed C-H Arylation of Aldoxime Using Oxime's Umpolung Properties.

Alkyl aldoximes without a directing group undergo palladium-catalyzed C-H arylation with aryl bromides to afford alkyl aryl ketoximes in moderate to high yields. The reaction of electron-rich aryl bromides and linear oximes proceeded to afford the coupling products in up to 98% yield. This reaction has broad scope and excellent functional group tolerance. Although reactions using hydroxyl oximes as nucleophiles have generally proceeded on the oxygen atom, this reaction selectively proceeds on oxime carbons by taking advantage of the oxime's umpolung properties and Pd reactivity.

Visible-Light-Induced Beckmann Rearrangement by Organic Photoredox Catalysis.

A facile and general strategy for efficient direct conversion of oximes to amides using an inexpensive organic photocatalyst and visible light is described. This radical Beckmann rearrangement can be performed under mild conditions. Various alkyl aryl ketoximes and diaryl ketoximes can be effectively converted into the corresponding amides in excellent yields.

Calcium Carbide as Acetylene Source in Cascade Assemblies of Hydroxypyrrolines and 3H‐Pyrroles from Ketoximes

AbstractTwo types of rare five‐membered aza‐heterocycles, namely 3,3‐disubstituted‐3H‐pyrroles and 5‐hydroxypyrrolines, were synthesized from calcium carbide and available sec‐alkyl (het)aryl ketoximes in the MOH/DMSO (M=Na, K) superbase systems. In contrast to the known procedures implemented with acetylene gas, the modified method is expedient and much safer that makes these intriguing aza‐heterocycles accessible for any laboratory without facilities working with acetylene gas.

Rh(III)‐Catalyzed Direct Amination of Aromatic Ketoximes Enabled by Potassium Acetate

A method to achieve rhodium(III)‐catalyzed, potassium acetate enabled intermolecular C–H amination of ketoximes using various benzenesulfonamide, especially 4‐nitrobenzenesulfonamide is reported. Various aryl ketoximes substituted with electron‐withdrawing functional groups were all well tolerated and produced the corresponding products in moderate to good yields. A preliminary mechanistic study revealed that potassium acetate is essential to realizing intermolecular amination.

Recent Developments in the Synthesis of 1,2,5-Thiadiazoles and 2,1,3-Benzothiadiazoles

The fast-growing interest in 1,2,5-thiadiazoles and their fused analogues including 2,1,3-benzothiadiazoles in recent years as important compounds in materials science and biomedicine has led to great progress in the synthesis of these heterocyclic systems. In this short review, the development of known procedures together with novel reactions is covered. New starting materials, unknown and unexpected transformations for the construction of the thiadiazole ring are emphasized.1 Introduction2 Synthesis of Monocyclic 1,2,5-Thiadiazoles2.1 From 1,2-Diamines, vic-Dioximes and Related Compounds2.2 From Alkyl Aryl (Hetaryl) Ketoximes and Tetrasulfur Tetranitride2.3 By Condensation Reactions2.4 From Other Heterocycles3 Synthesis of Fused 1,2,5-Thiadiazoles3.1 From ortho-Phenylenediamines and Related Compounds3.2 From ortho-Aminonitroso and ortho-Aminonitro Derivatives3.3 By Condensation Reactions3.4 By Chalcogen Exchange in 1,2,5-Oxa- and 1,2,5-Selenadiazoles3.5 Miscellaneous Methods4 Conclusions

Easy access to synthesize isoquinolines from aryl ketoximes and internal alkynes via Iridium (III)-catalyzed C[sbnd]H/N[sbnd]O bond activation

A highly efficient approach to synthesize isoquinoline derivatives through Iridium(III)-catalyzed cyclization of aryl ketoximes and internal alkynes without oxidant is reported. A broad range isoquinolines are obtained in good to excellent yields and various functional groups are well tolerated.

Synthesis and Anticandidal Activities of Some Aryl (5-Chloro-Benzofuran- 2-yl) Ketoximes

Background: In this study, some aryl (5-chloro-benzofuran-2-yl) ketoximes and their ethers were synthesised to evaluate their antifungal activity against C. albicans, C. glabrata, C. krusei, and C. parapsilosis. </p><p> Methods: The structure elucidation of the compounds was performed by IR, 1H-NMR, 13C-NMR and HR-MS spectroscopic data. ADME parameters of synthesised compounds 2a-2d, 3a-3d, 4a-4d were predicted by an in-silico study and it was determined that all synthesised compounds may have a good pharmacokinetic profile. </p><p> Results: In the anticandidal activity studies, compounds 2c and 3c were found to be the most active compounds. The effect of compound 2c, on ergosterol biosynthesis of C. albicans, was determined by using the LC-MS-MS method. </p><p> Conclusion: It was also docked in the active site of the lanosterol 14α-demethylase enzyme, and shown that there is a strong interaction between compound 2c and enzyme.

Synthesis of Some Aryl Ketoxime Derivatives with their in vitro Anti-microbial and Cytotoxic Activity

Benzofuwran derivatives found in several natural compounds and synthesized for various purposes. Due to their molecular structure’s electron behaviors they have several biological activities such as antitumor, cytotoxic, anticancer, antimicrobial, antifungal, ant proliferative etc. We synthesized (3-methyl-benzofuran-2-yl) ketoxime derivatives (one of them are new compound) and structure elucidation of the compounds was performed using IR, 1H-NMR, MASS spectroscopy and elemental analysis. X-Ray analysis of H2 compound was elucidated for the first time with this study in the literature. Cytotoxic activity against F2408 and HepG2 cell lines was also evaluated for the first time by MTT and NR uptake methods. Anti-microbial activity of H1, H2 and H3 was also investigated with broth micro dilution test. The results show that these ketoximes have cytotoxic and anti-microbial activity on different higher doses.

An Enantioselective Cpx Rh(III)-Catalyzed C-H Functionalization/Ring-Opening Route to Chiral Cyclopentenylamines.

A chiral Cpx RhIII catalyst system in situ generated from a Cpx RhI (cod) precatalyst and bis(o-toluoyl) peroxide as activating oxidant was developed for a C-H activation/ring-opening sequence between aryl ketoxime ethers and 2,3-diazabicyclo[2.2.1]hept-5-enes. This transformation provides access to densely functionalized chiral cyclopentenylamines in excellent yields and enantioselectivities of up to 97:3 er. The reported method is also well suitable for asymmetric alkenyl C-H functionalizations of α,β-unsaturated oxime ethers, furnishing skipped dienes with high levels of enantiocontrol.

An Enantioselective CpxRh(III)‐Catalyzed C−H Functionalization/Ring‐Opening Route to Chiral Cyclopentenylamines

AbstractA chiral CpxRhIII catalyst system in situ generated from a CpxRhI(cod) precatalyst and bis(o‐toluoyl) peroxide as activating oxidant was developed for a C−H activation/ring‐opening sequence between aryl ketoxime ethers and 2,3‐diazabicyclo[2.2.1]hept‐5‐enes. This transformation provides access to densely functionalized chiral cyclopentenylamines in excellent yields and enantioselectivities of up to 97:3 er. The reported method is also well suitable for asymmetric alkenyl C−H functionalizations of α,β‐unsaturated oxime ethers, furnishing skipped dienes with high levels of enantiocontrol.

Isoquinoline synthesis by C-H activation/annulation using vinyl acetate as an acetylene equivalent

Vinyl acetate is used as an acetylene equivalent in rhodium(III)-catalysed C-H activation/annulation with aryl ketoxime esters. Extension to an aldoxime ester allows for a concise formal synthesis of decumbenine B.

I2-Triggered N-O cleavage of ketoxime acetates for the synthesis of 3-(4-pyridyl)indoles.

A facile and complementary [3 + 2 + 1] annulation of aryl ketoxime acetates and 3-formylindoles to give pyridine derivatives is reported. The condensation reaction demonstrated that I2 was capable of triggering N-O bond cleavage of ketoxime acetates to generate iminyl radicals via a single electron transfer pathway. This direct and operationally simple protocol provides a fundamental platform to synthesize 3-(4-pyridyl)indoles with high functional group compatibility and high regioselectivity.

Synthesis of 5-hydroxy-Δ1-pyrrolines from sec-alkyl aryl ketoximes and acetylene

Synthesis of 5-hydroxy-Δ1-pyrrolines conjugated with aryl substituents has been effected via the rearrangement of O-vinylketoximes, having only one C–H bond adjacent to the oxime function and readily prepared by addition of sec-alkyl aryl ketoximes to acetylene. The target compounds were obtained in 80–86% yields (based on the O-vinylketoximes).

Easy Access to 1‐Amino and 1‐Carbon Substituted Isoquinolines via Cobalt‐Catalyzed CH/NO Bond Activation

AbstractA green atom‐economical method for the synthesis of highly functionalized 1‐amino and 1‐carbon substituted isoquinolines from the reaction of N′‐hydroxybenzimidamides and aryl ketoximes, respectively, with alkynes via pentamethylcyclopentadienylcobalt(III)‐catalyzed CH/NO bond activation is described. The external oxidant‐free annulation reaction uses the =NOH moiety in N′‐hydroxybenzimidamides or N‐aromatic ketone oximes as the directing group and internal oxidant. This first row transition metal‐catalyzed annulation serves as an efficient alternative for the synthesis of isoquinolines, as water is the only by‐product and expensive noble metals such as rhodium(III), iridium(III), palladium(II), and ruthenium(II) are not required. The reaction proceeds via CH activation, alkyne insertion, reductive elimination, and NO activation.magnified image

ChemInform Abstract: Synthesis of Sterically Congested Polycyclic Aromatic Hydrocarbons: Rhodium(III)‐Catalyzed Cascade Oxidative Annulation of Aryl Ketoximes with Diphenylacetylene by Sequential Cleavage of Multiple C—H Bonds.

AbstractThe scalable protocol for the synthesis of title compounds tolerates various functional groups.

Synthesis of Sterically Congested Polycyclic Aromatic Hydrocarbons: Rhodium(III)‐Catalyzed Cascade Oxidative Annulation of Aryl Ketoximes with Diphenylacetylene by Sequential Cleavage of Multiple CH Bonds

AbstractThe rhodium(III)‐catalyzed oxidative annulations of aryl ketoximes with diphenylacetylene by the cleavage of three CH bonds, one CO bond and the formation of four CC bonds, one CN bonds simultaneously have been developed. This protocol is scalable and compatible with various functional groups, providing an expeditious access to highly congested polycyclic aromatic/heteroaromatic hydrocarbons.magnified image