Parent Carbonyl Compounds Research Articles

Recent Update on Alkylation of Indole and Its Derivatives Using N‐Tosylhydrazone

AbstractN‐Tosylhydrazones are valuable synthons in various organic transformations to achieve potent bioactive heterocycles. N‐tosylhydrazones largely serve as 1,3‐dipolar species for cycloaddition reactions, diazo precursors for carbene or carbenoid reactions, and alternatives to parent carbonyl compounds. On the other hand, indole derivatives exhibit wide range of pharmacological and therapeutic activities including anticancer, antiviral, antimalarial, antiasthmatic, antibacterial and anti‐inflammatory. This review mainly highlights the recent developments in the synthetic usefulness of N‐tosylhydrazones derived from indole‐carboxaldehydes and other carbonyl compounds. Moreover, the synthetic potential, scope, limitations, and mechanism of these transformations have also been discussed.

Density Functional Theory Study on the Selective Reductive Amination of Aldehydes and Ketones over Their Reductions to Alcohols Using Sodium Triacetoxyborohydride.

Reductive amination is one of the most important methods to synthesize amines, having a wide application in the pharmaceutical, fine chemicals, and materials industries. In general, the reaction begins with dehydration between a carbonyl compound and an amine compound, forming an imine, which is then reduced to an alkylated amine product. Sodium triacetoxyborohydride (STAB) is a popular choice for the reducing agent as it shows selectivity for imines over aldehydes and ketones, which is particularly important in direct reductive amination where the imine and carbonyl compounds are present concurrently. Here, we analyze the reaction pathways of acid-catalyzed direct reductive amination in 1,2-dichloroethane (DCE) with acetaldehyde and methylamine. We find that the transition states for the formation and subsequent reduction of Z-methylethylideneimine (resultant aldimine from acetaldehyde and methylamine) have lower energies than the reduction of acetaldehyde. Transition state structures for the hydride transfers are organized by the Lewis-acidic sodium ion. Additionally, reduction reactions with formaldehyde and acetone and their imine derivatives (with methylamine) are investigated, and again, the hydride transfer to the resultant aldimine or ketimine is lower in energy than that of their parent carbonyl compound.

Catalytic Enantioselective Strecker Reaction of Isatin-Derived N-Unsubstituted Ketimines.

A catalytic enantioselective Strecker reaction of isatin-derived N-unsubstituted ketimines directly afforded the N-unprotected α-aminonitriles with a tetrasubstituted carbon stereocenter in up to 99% ee without requiring protection/deprotection steps. One-pot Strecker reactions from the parent carbonyl compounds were also realized with comparable yields and enantioselectivities. Direct transformations of the N-unprotected α-aminonitrile products streamlined the synthesis of unnatural amino acid derivatives and achieved the shortest one-pot stereoselective routes to a biologically active compound reported to date.

Luxury of N‐Tosylhydrazones in Transition‐Metal‐Free Transformations

AbstractThis review is focused on the recent developments in transition‐metal‐free transformations using N‐tosylhydrazones, emerging building blocks in contemporary organic chemistry. Emphasis is given to their synthetic potential, scope, mechanism and limitations. N‐Tosylhydrazones, derivatives of carbonyl compounds, can undergo a wide range of reactions under transition‐metal‐free reaction conditions. The chemical behaviour of tosylhydrazones is unique under different reaction conditions as they can act as diazo precursors, carbene sources, 1,3‐dipoles, ambiphilic reagents, one‐carbon synthons, and an alternative to the parent carbonyl compounds. These diverse reactivities have resulted in the development of novel C−C and C−heteroatom bond‐forming reactions. The potential of N‐tosylhydrazones in transition‐metal‐free reactions is evident from the synthesis of a handful of molecules such as cyclopropanes, di‐ and triarylmethanes, pyrazoles, triazoles, pyridazines, ethers, carbamates, thioacetals, thiadiazoles and many others.magnified image

1,2-Addition or Enolization? Variable Reactivity of a Cerium Acetylide Complex toward Carbonyl Compounds

The reactions of the cerium alkyne complex bearing 2,6-bis(dimethylamino)-4-methylphenolate supporting ligands (bdmmp) and a terminal acetylide moiety, Na[Ce(C≡CPh)(bdmmp)3] (1), with benzaldehyde and a family of enolizable ketones led to different products depending on the acidity of the parent carbonyl compound. The reactions of 1 with benzaldehyde, acetone, benzylideneacetone, or 1,1-diphenylacetone (pKaDMSO = 26.5–19.4) gave the products of nucleophilic addition of type Na[Ce(O-CR2-C≡CPh)(bdmmp)3] featuring a new C–C bond. In contrast, the reaction of 1 with β-tetralone (pKaDMSO = 17.6) resulted in the enolization and deprotonation of β-tetralone with subsequent replacement of the acetylide ligand at the cerium ion by the enolate. Molecular structures for the cerium products were determined by X-ray diffraction studies, providing valuable information about the performance of organocerium reagents.

ChemInform Abstract: Developments in Synthetic Application of Selenium(IV) Oxide and Organoselenium Compounds as Oxygen Donors and Oxygen‐Transfer Agents

AbstractReview: 192 refs.

Developments in Synthetic Application of Selenium(IV) Oxide and Organoselenium Compounds as Oxygen Donors and Oxygen-Transfer Agents.

A variety of selenium compounds were proven to be useful reagents and catalysts for organic synthesis over the past several decades. The most interesting aspect, which emerged in recent years, concerns application of hydroperoxide/selenium(IV) oxide and hydroperoxide/organoselenium catalyst systems, as “green reagents” for the oxidation of different organic functional groups. The topic of oxidations catalyzed by organoselenium derivatives has rapidly expanded in the last fifteen years This paper is devoted to the synthetic applications of the oxidation reactions mediated by selenium compounds such as selenium(IV) oxide, areneseleninic acids, their anhydrides, selenides, diselenides, benzisoselenazol-3(2H)-ones and other less often used other organoselenium compounds. All these compounds have been successfully applied for various oxidations useful in practical organic syntheses such as epoxidation, 1,2-dihydroxylation, and α-oxyfunctionalization of alkenes, as well as for ring contraction of cycloalkanones, conversion of halomethyl, hydroxymethyl or active methylene groups into formyl groups, oxidation of carbonyl compounds into carboxylic acids and/or lactones, sulfides into sulfoxides, and secondary amines into nitrones and regeneration of parent carbonyl compounds from their azomethine derivatives. Other reactions such as dehydrogenation and aromatization, active carbon-carbon bond cleavage, oxidative amidation, bromolactonization and oxidation of bromide for subsequent reactions with alkenes are also successfully mediated by selenium (IV) oxide or organoselenium compounds. The oxidation mechanisms of ionic or free radical character depending on the substrate and oxidant are discussed. Coverage of the literature up to early 2015 is provided. Links have been made to reviews that summarize earlier literature and to the methods of preparation of organoselenium reagents and catalysts.

Selective oxidative deoximation with anhydrous Ce(IV) sulfate

Anhydrous Ce(SO4)2 in chloroform selectively converts oximes into the parent carbonyl compounds in good yields. Hammett correlations helped to indicate a plausible mechanism for the above reaction. The formation of 1-(dinitromethyl)benzene was assumed to be a product of isonitroso hydrogen reaction with arylaldoximes.

Photoremoval of Protecting Groups: Mechanistic Aspects of 1,3-Dithiane Conversion to a Carbonyl Group

Photodeprotection of 1,3-dithianes in the presence of thiapyrylium was performed to return to the parent carbonyl compound, and the mechanism was studied by steady state photolysis, laser flash photolysis, and theoretical calculations. Electron transfer from dithianes to triplet sensitizers is extremely fast, and the decay of dithiane radical cations was not affected by the presence of water or oxygen as the consequence of a favorable unimolecular fragmentation pathway. Similar behaviors were observed for dithianes bearing electron-releasing or electron-withdrawing substituents on the aryl moiety, evidenced by C-S bond cleavage to form a distonic radical cation species. The lack of reaction under nitrogen atmosphere, requirement of oxygen for good conversion yields, inhibition of the photodeprotection process by the presence of p-benzoquinone, and absence of a labeled carbonyl final product when the reaction is performed in the presence of H2(18)O all suggest that the superoxide anion drives the deprotection reaction. Density functional theory computational studies on the reactions with water, molecular oxygen, and the superoxide radical anion support the experimental findings.

Preparation of Unsymmetrical Ketones from Tosylhydrazones and Aromatic Aldehydes via Formyl C–H Bond Insertion

Preparation of ketones by insertion of diazo compounds into the formyl C-H bond of an aldehyde is an attractive procedure, but use of structurally diverse diazo compounds is hampered by preparation and safety issues. A convenient procedure for the synthesis of unsymmetrical ketones from bench-stable tosylhydrazones and aryl aldehydes is reported. The procedure can be performed in one pot from the parent carbonyl compound and needs only a base, with no additional promoters being required.

Silica Phenyl Sulfonic Acid as a Solid Acid Heterogeneous Catalyst for Chemoselective Thioacetalization of Carbonyl Compounds and Dethioacetalization under Mild Conditions

Silica phenyl sulfonic acid (SPSA) is an effective catalyst for chemoselective thioacetalization of aldehydes in the presence of ketones under neutral conditions. In addition, a simple and an efficient procedure for deprotection of 1,3‐dithianes and 1,3‐dithiolanes of aromatic, aliphatic, and α,β‐unsaturated aldehydes and ketones in the solvent‐free to the corresponding parent carbonyl compounds was successfully carried out with SPSA in excellent yields.

Protection and deprotection chemistry catalyzed by zirconium oxychloride octahydrate (ZrOCl2·8H2O)

An efficient, chemoselective, convenient, and straightforward methodology has been developed for the protection of C=O group of aldehydes/ketones as C=N moiety of hydrazones catalyzed by ZrOCl2·8H2O (10 mol%) in acetonitrile and the same catalyst in methanol oxidatively cleaves C=N moiety of hydrazones to provide parent carbonyl compounds in high yields. The reactions have been performed in aerobic condition. The catalyst is inexpensive, readily available, easy to handle, insensitive to air and moisture, easily recoverable and can be reused and importantly less toxic.

ChemInform Abstract: Rapid and Efficient Method for Room Temperature Deoximation Reaction under Solvent‐Free Conditions.

Department of Chemistry ,Dibrugarh University, Dibrugarh 786004, Assam, IndiaReceived April 27, 2011, Accepted June 1, 2011Key Words : Deoximation, Solvent-free, Vanadium polyoxometalateThe cleavage of oximes to regenerate the parent carbonylcompounds is an important synthetic process as oximes areuseful protecting groups in multistep organic synthesis

Rapid and Efficient Method for Room Temperature Deoximation Reaction Under Solvent-Free Conditions

Department of Chemistry ,Dibrugarh University, Dibrugarh 786004, Assam, IndiaReceived April 27, 2011, Accepted June 1, 2011Key Words : Deoximation, Solvent-free, Vanadium polyoxometalateThe cleavage of oximes to regenerate the parent carbonylcompounds is an important synthetic process as oximes areuseful protecting groups in multistep organic synthesis

Identification of the chlorination products of aliphatic ketones by gas chromatography and gas chromatography/mass spectrometry

The differences in the gas chromatographic retention indices of the chlorination products of aliphatic ketones and parent carbonyl compounds (ΔRI) are constant, and their numeric values depend on the number and position of chlorine atoms in the molecule. A simplest version of an additive scheme for the evaluation of retention indexes is developed to identify the chloro derivatives of carbonyl compounds. The order of the chromatographic elution of diastereomeric α,α′-dichloro-k-alkanones (k > 2) is found.

Gas chromatographic identification of chlorination products of aliphatic ketones

Chlorinated derivatives of aliphatic ketones are a class of organic compounds poorly characterized by both mass spectra and chromatographic retention indices up to present. It is caused by objective difficulties of isolation of individual products from reaction mixtures formed in the result of non-selective chlorination of parent carbonyl compounds. Nevertheless the differences of GC retention indices for structurally analogous chlorination products of different ketones and initial substrates indicate the constancy depending on the number and position of chlorine atoms in the molecules. This feature permits us to use the simplest kind of additive schemes in identification of such chlorinated derivatives, including diastereomeric α,α′-dichloro- k-alkanones ( k > 2). Hence, the identification of chlorination products of aliphatic ketones becomes possible for any compounds of this class without using mass spectrometric data only in the result of accurate measurement of their GC retention indices.

1,3-Dibromo-5,5-dimethylhydantoin (DBH) as a Mild and Efficient Catalyst for Chemoselective Thioacetalization of Carbonyl Compounds and Dethioacetalization Under Mild Conditions

Hydantoin bromide is an effective catalyst for chemoselective thioacetalization of aldehydes in the presence of ketones under neutral conditions. In addition, a simple and efficient procedure for the deprotection of 1,3-dithianes and 1,3-dithiolanes of aromatic, aliphatic, and α,β-unsaturated aldehydes and ketones in solvent-free conditions to the corresponding parent carbonyl compounds was successfully carried out with hydantoin bromide in excellent yields. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Deoximation of Ketoximes to Ketones with Ammonium Chlorochromate/Montmorillonite K10 in Dichloromethane

A convenient, mild and efficient method for oxidative cleavage of ketoximes to their parent carbonyl compounds with ammonium chlorochromate (ACC) / montmorillonite K10 in dichloromethane at room temperature is described

Cleavage of 1,3-Dithianes via Acid-Catalyzed Hydrolysis of the Corresponding 1,3-Dithianemonooxides

The hydrolysis of 1,3-dithianes to their parent carbonyl compounds via their corresponding monosulfoxides was systemati- cally investigated. The oxidation of the 1,3-dithianes was carried out in high yields using tert-butyl hydroperoxide. Acid-catalyzed hydrolysis of the monosulfoxides to the carbonyl compounds was then performed in excellent yields. The cleavage reactions were monitored by gas chromatography and kinetics were investigated on substrates varying in electron density and steric requirements. Neither effect prevented high overall yields in the cleavage reac- tion.

Reactions of polycyclic thioketones with a phosphonylated carbanion

AbstractPolycyclic, nonenolizable cycloaliphatic thioketones 1a and 1b react smoothly with the lithium salt of diethyl methylphosphonate 7 in THF solution at −40°C to afford products of the carbophilic attack exclusively. Quenching of the obtained lithium thiolates with alkyl iodides yields sulfanes of type 9 or 11, respectively, in good yields. 1‐Fluoro‐2,4‐dinitrobenzene was shown to act as an arylating agent. In the case of the “cage” thioketone 1b, the carbanion of salt 7 approaches the CS bond from the exo‐side exclusively. In contrast to the parent carbonyl compounds, thioketones 1 show no tendency to undergo the conversion analogous to the Horner–Wadsworth–Emmons reaction, which would result in the formation of an olefinic product. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:182–187, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20390