Ketone Functionality Research Articles

Multisubstituted Cyclohexene Construction through Telescoped Radical-Addition Induced Remote Functional Group Migration and Horner-Wadsworth-Emmons (HWE) Olefination.

An efficient telescoped method for the rapid assembly of multisubstituted cyclohexenes is presented herein. The whole process nicely merges photoredox-promoted alkene difunctionalization via remote functional group migration with concomitant intramolecular Horner-Wadsworth-Emmons (HWE) olefination. The characteristic feature of this protocol resides in the fact that the follow-up requiring ketone functionality for ring-closing olefination is in situ unveiled from the otherwise inert tertiary alcohol by the preceding alkene difunctionalization.

The 1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides in Water Media

The 1,3-dipolar Cycloadditions (DCs) of Nitrile Oxides (NOs) have been used as a powerful tool in synthetic organic chemistry. The cycloadducts arising from Cycloadditions (CAs) of NOs to alkenes and alkynes (2-isoxazolines and isoxazoles respectively) are valuable synthetic intermediates because, among others, their capacity to mask other functionalities including α, β -unsaturated ketones, β -hydroxy carbonyl compounds and 1,3- aminoalcohols. In particular, the β-hydroxy ketone functionality is an illustrative example, making the NOs alkenes CAs reactions a synthetically equivalent methodology of aldol reactions. The vast majority of these reactions are carried out in organic solvents. Nevertheless, the use of water as an alternative solvent has evident advantages on the “Green Chemistry” concept. The critical discussion on the use of water instead of “conventional” solvents in the 1,3-DCs reactions of NOs is the objective of the present review.

Unraveling the role of reaction environment and catalysts for pyrolysis of technical lignin into different functional bio-oil yield

Catalytic pyrolysis of Kraft Lignin (KL) experiments were carried out at different temperatures (350–500 °C) over base MgO, acidic ZSM-5 and mixture of MgO-ZSM-5 catalysts under different environments (N2 and CO2). Non-catalytic reaction produced maximum bio-oil (35.3 wt%) under CO2 at 450 °C. Upgrading of pyrolysis vapor under different environment with catalysts produced lower bio-oil as it is enhanced cracking and coke formation. Higher intensity peak at 1695–1720 cm-1 was found in up-gradation pyrolysis KL vapor under CO2, which showed that the higher aldehyde/acidic or ketone functionality in bio-oil. The content of monocyclic aromatic hydrocarbons increased whereas phenolic compound decreased with using the catalysts under N2 while acidic functionality increased under CO2 environment. Our results suggest that mixture of catalysts showed synergistic effects which increased the bio-oil quality. Overall, mixture of MgO-ZSM-5 showed the highest yield of aromatic hydrocarbons (ca. 49.2%) under N2. Significant amount oxygen content reduced with the mixture of catalyst (MgO-ZSM-5, 1:1 ratio) under N2 with the increasing of aromatic hydrocarbon. Higher heating value bio-oil was obtained with catalytic up-gradation.

Asymmetric Total Synthesis of Shagenes A and B.

We report the first total synthesis of shagenes A and B, which are tricyclic terpenoids containing a cis-substituted cyclopropane, via ring-closing metathesis of an enamide and Ir-catalyzed double-bond isomerization of an alkylidenecyclopropane. Chemo- and diastereoselectivity in the distorted cis-substituted structures were controlled by the alkylidenecyclopropane reactivity and using the ketone functionality as a remote directing group for the Ir catalyst, respectively. The total synthesis suggested the absolute configuration of shagenes.

Asymmetric Total Synthesis of Shagenes A and B

AbstractWe report the first total synthesis of shagenes A and B, which are tricyclic terpenoids containing a cis‐substituted cyclopropane, via ring‐closing metathesis of an enamide and Ir‐catalyzed double‐bond isomerization of an alkylidenecyclopropane. Chemo‐ and diastereoselectivity in the distorted cis‐substituted structures were controlled by the alkylidenecyclopropane reactivity and using the ketone functionality as a remote directing group for the Ir catalyst, respectively. The total synthesis suggested the absolute configuration of shagenes.

An Approach for the Synthesis of Pyrazolo[1,5-a]pyrimidines via Cu(II)-Catalyzed [3+3] Annulation of Saturated Ketones with Aminopyrazoles.

A one-step synthesis of diversely substituted pyrazolo[1,5-a]pyrimidines from saturated ketones and 3-aminopyrazoles is presented. This transformation involves the in situ formation of α,β-unsaturated ketones via a radical process, followed by [3+3] annulation with 3-aminopyrazoles in one pot. Mechanistic studies have shown that the dual C(sp3)-H bond functionalization of inactive ketones is required for the formation of the title compounds. Notably, this dehydrogenative coupling process provides access to a host of functionalized pyrazolo[1,5-a]pyrimidines with antitumor potential from commercially available substrates.

Influence of ligand geometry on cholinesterase enzyme - A comparison of 1-isoindolinone based structural analog with Donepezil

Donepezil (DNPZ) is one of the few FDA-approved widely used medication in the clinical care of Alzheimer's disease (AD) patients. To investigate the effect of geometry and to find the significance of an enol form if any in DNPZ on acetylcholinesterase (AChE) inhibition, we changed the tetrahedral geometry of DNPZ to planar trigonal pyramidal geometry by replacing the α-carbon atom next to ketone functionality with a nitrogen atom. To mimic 1-indanone in DNPZ, we selected 1-isoindolinone framework to synthesize 25 new DNPZ derivatives and characterized using 1H NMR, 13C NMR and ESI-MS spectroscopy methods. Drug likeliness profile for each compound was predicted using Molinspiration online software following Lipinski's rule. Commercially available assay kits were used to measure AChE and butyrylcholinesterase (BuChE) inhibitory effects. NIH/3T3 mouse embryonic fibroblast cell line was used to measure cytotoxic and proliferation effects using LDH and MTT assay, respectively. Compound #20 was selected for comparative computational docking, modelling and physicochemical studies. Our results show that DNPZ with tetrahedral geometry has 3-fold higher AChE inhibition as compared to compound #20 with planar trigonal pyramidal geometry. Our approach may be useful as a novel indirect method to study the significance of the enol form in DNPZ (or similar compounds), since constant interconversion between the keto and enol forms does not permit a direct determination of the effect of the enol form of DNPZ in vivo. Overall, we conclude that the tetrahedral is a better fit and any change in geometry significantly drives down the cholinesterase inhibitory effect of DNPZ.

Exploring the Monoterpene Indole Alkaloid Scaffold for Reversing P-Glycoprotein-Mediated Multidrug Resistance in Cancer

Dregamine (1), a major monoterpene indole alkaloid isolated from Tabernaemontana elegans, was submitted to chemical transformation of the ketone function, yielding 19 azines (3–21) and 11 semicarbazones (22–32) bearing aliphatic or aromatic substituents. Their structures were assigned mainly by 1D and 2D NMR (COSY, HMQC, and HMBC) experiments. Compounds 3–32 were evaluated as multidrug resistance (MDR) reversers through functional and chemosensitivity assays in a human ABCB1-transfected mouse T-lymphoma cell model, overexpressing P-glycoprotein. A significant increase of P-gp inhibitory activity was observed for most derivatives, mainly those containing azine moieties with aromatic substituents. Compounds with trimethoxyphenyl (17) or naphthyl motifs (18, 19) were among the most active, exhibiting strong inhibition at 0.2 µM. Moreover, most of the derivatives showed selective antiproliferative effects toward resistant cells, having a collateral sensitivity effect. In drug combination assays, all compounds showed to interact synergistically with doxorubicin. Selected compounds (12, 17, 18, 20, and 29) were evaluated in the ATPase activity assay, in which all compounds but 12 behaved as inhibitors. To gather further insights on drug–receptor interactions, in silico studies were also addressed. A QSAR model allowed us to deduce that compounds bearing bulky and lipophilic substituents were stronger P-gp inhibitors.

Synthesis of (+)-Panamonon B, 7-epi-Panamonon B, and Their (Z)-Isomers.

(+)-Panamonon B was synthesized with the key quaternary center (of a predefined absolute configuration) installed using Stoltz asymmetric allylation. The C-5 ketone functionality and the cross-conjugated enone moiety in the side chain were introduced via a photosensitized [2+4] cycloaddition of singlet oxygen to diene silyl enol ether and an aldol condensation under the conditions of Sugiura, respectively. The 1H and 13C NMR of the synthetic and natural samples were fully consistent with each other. However, because two samples showed opposite signs for optical rotations, they must be antipodes to one another. The synthesis also provided valuable chances to observe unexpected, yet rather intriguing, phenomena such as a bulky substituent in an axial position of a cyclohexane ring and (E)-and (Z)-isomers with opposite signs for optical rotations despite their identical stereogenic centers. The rare occurrence of a bulky substituent in an axial position of a cyclohexane ring is rationalized as a consequence of the presence of a quaternary center and formation of the five-membered lactone fused to the six-membered ring, while the so far unnoticed influence of C═C geometry on optical rotation is shown to be consistent with the information encapsulated in several discrete pairs of similar compounds retrieved from the literature.

Palladium-Catalyzed ortho-C–H Functionalization of Aromatic Ketones for Site-Selective Fluorination

Palladium-Catalyzed ortho-C–H Functionalization of Aromatic Ketones for Site-Selective Fluorination

Radical Cyclization of Olefinic Amides through α-C(sp3)–H Functionalization of Ketones under Catalyst-, Ligand-, and Base-Free Conditions

AbstractA new, efficient, and practical radical cyclization of olefinic amides with ketones through α-C(sp3)–H functionalization in the presence of tert-butyl peroxybenzoate (TBPB) is described for the first time. This protocol assembles a wide range of pivotal and useful benzoxazines in good to excellent yields under mild, catalyst-free, ligand-free, and base-free conditions with wide functional group tolerance. Moreover, the mechanistic study indicates that the α-carbonyl radical is involved in this transformation.

Viable route and DFT study for the synthesis of optically active limonaketone: A barely available natural feedstock in Cedrus atlantica

Herein, we report a novel, easy and efficient synthesis pathway of optically active limonaketone, a high added value monoterpene, starting from limonene, natural and low-cost feedstock. The strategy was developed in an excellent three-step total synthesis of limonaketone, potentially important intermediate in limonene ozonolysis and barely available in Cedrus atlantica essential oil (0.1% yield). The first step was the epoxidation of limonene which proceed in 91% yield. The ozonolysis of the prepared limonene oxide leads to the formation of the characteristic ketone function of limonaketone in 92% yield. The last step was performed by a deoxygenation in the presence of Zn and gave limonaketone in quantitative yield. The optically pure limonaketone has been efficiently synthesized from limonene and the overall yield was 84%. A molecular electron density theory (MEDT) analysis was carried out by using density functional theory (DFT) calculations at the M06–2X/6–311G(d,p) (LANL2DZ for Zn) level to understand the observed chemoselectivity in the Zn-deoxygenation reaction as well as its corresponding mechanistic pathway.

Advances in Transition‐Metal Catalyzed Carbonylative Suzuki‐Miyaura Coupling Reaction: An Update

AbstractTransition metals have been an indispensable component of modern catalysis and among these palladium is the top‐ranked choice of chemists as a catalyst. After the several important developments of palladium catalysed C−C cross‐coupling reactions, carbonylative transformations have been realised as an attractive post modification of these reactions. Carbonylative Suzuki‐Miyaura coupling reaction is among such transformations for direct incorporation of CO fragment for the preparation of biaryl or aryl/alkyl ketones via transition‐metal catalysis. Ketone functionality is basically a valuable building block having huge pharmaceutical and agrochemical applications. Moreover, carbonylative Suzuki‐Miyaura coupling is also used in the synthesis of various natural bioactive molecules through the direct joining of molecular fragments via CO bridge. In this review, the past decade developments in the carbonylative Suzuki‐Miyaura coupling reactions are documented in detail with modern approaches in transition‐metal catalysis.magnified image

A DFT mechanistic study on oxidative dehydrogenative Diels–Alder reaction of alkylbenzenes

Cross-dehydrogenative Diels-Alder cycloaddition reaction between readily-available alkyl benzenes and electron-deficient dienophiles is an attractive synthetic route to access carbocyclic compounds which have high utility in the chemical and pharmaceutical industries. This work reports a study at the M06-2X/6-311G(d) and M06-2X/6–311++G(d,p) levels of theory on the reaction of alkyl benzenes with electron-deficient dienophiles in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an oxidant and hydroquinone as an activator, so as to understand the chemoselectivity of the reaction (addition across the alkene functionality versus the ketone functionality), the role of the activator, the effects of substituents and the effect of solvent on the reaction. The results show the addition of the alkene bonds of methylstyrene across the alkene functionality of the electron-deficient dienophiles has generally low barriers compared to the addition across the carbonyl functionality of the electron-deficient dienophile. Powerful electron-withdrawing group (cyano) on the electron-deficient dienophile decrease the energy barrier for the cycloaddition and decrease the stability of the product whiles weak electron-withdrawing (bromine and chlorine) and electron-donating groups increase the energy barrier for the cycloaddition and decrease the stability of the product. The hydroquinone as an activator decreases the activation barrier for the Diels-Alder cycloaddition reaction.

Convenient synthesis of 4,5-unsubstituted 3-aroylisoxazoles from methyl aryl ketones and (vinylsulfonyl)benzene in water

A convenient synthesis of 3-aroylisoxazoles from methyl ketones and (vinylsulfonyl)benzene in 2%TPGS-750-M/H2O has been developed. This reaction proceeds via tandem tert-butyl nitrite-promoted Csp3-H functionalization of methyl ketones, 1,3-dipolar cycloaddition and base-catalyzed aromatization, providing the corresponding products in moderate to good yields.

Recent progress in the radical α-C(sp3)-H functionalization of ketones.

The direct use structurally simple ketones as α-ketone radical sources for α-C(sp3)-H functionalization is a sustainable and powerful approach for constructing complex and multifunctional chemical scaffolds with diverse applications. The reactions of α-ketone radicals with alkenes, alkynes, enynes, imides, and imidazo[1,2-a]pyridines have broadened the structural diversity and complexity of ketones. Through chosen illustrative examples, we outline the recent progress in the development of methods that enable the radical α-C(sp3)-H functionalization of ketones, with an emphasis on radical initiation systems and possible mechanisms of the transformations. The application of these strategies is illustrated by the synthesis of several biologically active molecules and drug molecules. Further subdivision is based on substrate type and reaction type.

IR spectral fingerprints of carbonyl groups in graphite oxide: a theoretical study

Non-empirical quantum chemical calculations of various possible fragments in the oxidized carbon layer of graphite oxide were carried out at the DFT level with the hybrid B3LYP functional and the extended double-zeta Gaussian basis set. These fragments contain the carbonyl groups as ketone, carboxyl and lactone functions, either free or hydrogenbonded to hydrating water molecules or closely arranged hydroxyl groups. Using the vibrational energy distribution analysis, the typical spectral ranges of C=O vibrations were identified within the fingerprint region of 1550–1800 cm−1 depending on the kind of the carbonyl group studied and its environment.

Selective, Catalytic Oxidations of C–H Bonds in Polyethylenes Produce Functional Materials with Enhanced Adhesion

Summary The synthesis of functional and processable polyethylenes from simple vinyl monomers with controlled molecular weights and architectures has been a grand challenge of polymer chemistry. Post-polymerization modification of the homopolymers of ethylene is attractive for this purpose but has been hampered by the lack of efficient methods for the selective functionalization of C–H bonds in polyolefins. We report the selective, catalytic oxidation of C–H bonds in commodity polyethylenes with varying molecular weights and architectures. Remarkably, the functionalized materials, even at low levels of functionalization, exhibit physical properties that are absent in unmodified polyolefins, such as strong adhesion and the ability to be painted with common waterborne latex paint. Such observations indicate that selectively modified polyethylenes as described here may help to transform existing commodity plastics into more valuable and potentially more sustainable materials.

Exploration of Mesyl Chloride in a One Pot Conversion of Carboxylic Acids to Ketones

Background: Due to the ubiquitous nature of the ketone functionality, it is considered an important functional group in organic chemistry. Hence, the synthesis of ketones from readily available starting materials is an important chemical transformation in organic synthesis. Consequently, several research efforts have been reported in the literature for the transformation of carboxylic acids to ketones in a one-pot synthesis. However, some of the procedures have limitations, such as long reaction times, harsh reaction conditions, and usage of expensive metal catalysts. Thus, a simple and convenient one-pot conversion of carboxylic acids to ketones remains desirable. Objective: We intended to develop a simple and convenient one-pot methodology for the synthesis of ketones from carboxylic acids. Our objective was to build up a carboxylic acid-based chemical template where various types of organometallic reagents can interact to produce the desired ketone. Methods: In this procedure, a carboxylic acid was converted to a mixed anhydride using mesyl chloride in the presence of a base. This mixed anhydride was then reacted with a suitable organometallic reagent at -20°C to obtain the desired ketone. The reaction was performed in a one-pot fashion. Results: Under the optimized reaction conditions, various aromatic and heteroaromatic carboxylic acids were converted to the corresponding ketones using organolithium and organomagnesium reagents with short reaction times. Moderate to good yields of the desired ketones were observed in many of these transformations. Conclusion: A simple and convenient one-pot method for the conversion of carboxylic acids to ketones has been reported. Specifically, various aromatic and `heteroaromatic carboxylic acids have been converted to the corresponding ketones in moderate to good yields. Organomagnesium and organolithium reagents were used as nucleophiles for this reaction.

New Ophiobolins from the Deep-Sea Derived Fungus Aspergillus sp. WHU0154 and Their Anti-Inflammatory Effects.

Deep-sea fungi have become a new arsenal for the discovery of leading compounds. Here five new ophiobolins 1–5, together with six known analogues 6–11, obtained from a deep-sea derived fungus WHU0154. Their structures were determined by analyses of IR, HR-ESI-MS, and NMR spectra, along with experimental and calculated electronic circular dichroism (ECD) analysis. Pharmacological studies showed that compounds 4 and 6 exhibited obvious inhibitory effects on nitric oxide (NO) production induced by lipopolysaccharide (LPS) in murine macrophage RAW264.7 cells. Mechanical study revealed that compound 6 could inhibit the inducible nitric oxide synthase (iNOS) level in LPS-stimulated RAW264.7 cells. In addition, compounds 6, 9, and 10 could significantly inhibit the expression of cyclooxygenase 2 (COX 2) in LPS-induced RAW264.7 cells. Preliminary structure-activity relationship (SAR) analyses revealed that the aldehyde group at C-21 and the α, β-unsaturated ketone functionality at A ring in ophiobolins were vital for their anti-inflammatory effects. Together, the results demonstrated that ophiobolins, especially for compound 6, exhibited strong anti-inflammatory effects and shed light on the discovery of ophiobolins as new anti-inflammatory agents.