Ketene Chemistry Research Articles

Thermosetting resins with high fractions of free volume and inherently low dielectric constants.

This work demonstrates a new class of thermosetting resins, based on Meldrum's acid (MA) derivatives, which have high fractions of free volume and inherently low k values of about 2.0 at 1 MHz. Thermal decomposition of the MA groups evolves CO2 and acetone to create air-trapped cavities so as to reduce the dielectric constants.

ChemInform Abstract: New Directions in Ketene Chemistry: The Land of Opportunity

AbstractReview: 85 refs.

Photoinduced grafting of polystyrene onto silica particles by ketene chemistry

This study describes a novel route for incorporation of polymers onto silica particle surfaces to prepare polymer/silica nanocomposites. Photoinduced formation of ketene functionalities at the polystyrene chain ends offers possibility of such ligation through ketene chemistry.

New Directions in Ketene Chemistry: The Land of Opportunity

AbstractSelected recent developments in ketene chemistry are described. They include examples of stereoselective reactions, ketenes and polymers, ketenes and carbenes, ketenes in synthesis, ketenes from photochemical processes, and bis‐β‐lactam formation.

Practical Synthesis of a Neuropeptide Y Antagonist via Stereoselective Addition to a Ketene

[Reaction: see text]. The synthesis of neuropeptide Y antagonist 1, currently under clinical investigation for the treatment of obesity, is described. The convergent synthesis from trans-spirolactone carboxylic acid intermediate 2a and aminopyrazole 3 is predicated on a stereoselective route to the former. The coupling reaction of ethyl 4-oxocyclohexanecarboxylate (10a) with lithiated isonicotinamide 11 was investigated in detail, but even optimized conditions only provided a 45:55 ratio of trans:cis isomers (12a:12b). While selective crystallization schemes were developed to isolate the thermodynamically less stable trans isomer 2a, improved stereocontrol was subsequentially achieved by the application of ketene chemistry. The ketene formation and quench was investigated under a variety of conditions aimed at maximizing the trans:cis ratio. Reacting a mixture of carboxylic acids 2a and 2b with POCl3 in THF, followed by concomitant addition of tert-butyl alcohol in the presence of TMEDA at 35 degrees C provided a 4:1 ratio of trans:cis tert-butyl esters (18a:18b) via in situ ketene formation. Ester hydrolysis, followed by selective crystallization of undesired 2b as the HCl salt, led to isolation of 2a in 47% overall yield. Aminopyrazole intermediate 3 was synthesized via the condensation reaction of 2-fluorophenylhydrazine hydrochloride (4a) with acrylonitrile derivative 5 in 65-70% yield. Coupling of advanced intermediates 2a and 3b via activation with thionyl chloride gave a 92% yield of 1.

Ketenes in Polymer-Assisted Synthesis

For Abstract see ChemInform Abstract in Full Text.

Ketenes in polymer-assisted synthesis.

Since its inception, ketene chemistry has developed into a unique and well-established source of useful transformations for conventional synthetic organic chemistry. It is, therefore, not surprising that soon after their movement from the realm of peptide and peptoid libraries to that of small molecules, combinatorial chemists have sought the benefits of ketene chemistry to satisfy their own synthetic needs. The ability of these versatile molecules to undergo reactions with nucleophiles, and to participate in cycloadditions and cyclocondensations, has been utilized for the preparation of diverse heterocyclic compounds, and has added to the advantages of polymer-assisted synthesis for rapid purification. Different types of ketenes and different methods for their generation have been involved, which illustrates the potential diversity of the chemistry. There is now a better grasp of the effect of the fragility of these sometimes transient molecules on the reactions involving solid supports, and this augurs well for the application of some of the more recent developments in ketene chemistry to the generation of small-molecule libraries.

ChemInform Abstract: Development in Ketene Chemistry: Generation and Reaction of α‐Oxoketenes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ketene Recognizes 1,3-Dienes in Their s-Cis Forms through [4 + 2] (Diels−Alder) and [2 + 2] (Staudinger) Reactions. An Innovation of Ketene Chemistry

The mechanism of ketene−diene reactions has been studied both experimentally and theoretically. Careful experiments of the reactions of diphenylketene (1) with cyclic (s-cis) 1,3-dienes [cyclopentadiene (2) and cyclohexa-1,3-diene (3)] lead to the first direct detection of the Diels−Alder cycloadducts (10 and 11) by low-temperature NMR spectroscopy. The initially formed cycloadducts are converted to the final Staudinger products, cyclobutanones (6 and 7), by [3,3] sigmatropic (Claisen) rearrangements. In contrast, ketene 1 reacts with open-chain 1,3-dienes [2,3-dimethyl-1,3-butadiene (4) and 1-methoxy-1,3-butadiene (5)] to afford initially both the Staudinger-type (8, 9) and Diels−Alder-type cycloadducts (12, 13). The Staudinger cycloadducts (8, 9) are converted eventually to Diels−Alder products (12, 13) by the retro-Claisen rearrangement. Thus, ketene recognizes dienes in cycloadditions as ketenophiles different from olefins. [4 + 2] and [2 + 2] cycloadducts are generated and can be intermediates or pro...

The Problem of Non-Recognition for Dienes in Ketene Reactions

Non-recognition for dienes in ketene reactions has long been an important problem in organic chemistry since the diphenylketene-cyclopentadiene reaction was found by Staudinger in 1920. Recently, we have discovered that the ketene recognizes conjugated dienes. The ketene is a dienophile not for well-known [2+2] cycloadditions but for [4+2] (Diels-Alder) reactions across its C=O bond. This paper outlines the long history of ketene chemistry and describes the way of how the problem has been tackled. The frontier-orbital theory and ab initio calculations have predicted that ketene should react with cyclopentadiene via the [4+2] cycloaddition and a subsequent Claisen rearrangement. Careful low-temperature experiments and NMR spectroscopy of the reaction have demonstrated the first detection of the [4+2] -type cycloadduct and the conversion to the final product, cyclobutanone, by the rearrangement.

Silylated bisketenes: Accessible and reactive organic intermediates

Abstract

Ketene chemistry: the second golden age

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKetene chemistry: the second golden ageThomas T. TidwellCite this: Acc. Chem. Res. 1990, 23, 9, 273–279Publication Date (Print):September 1, 1990Publication History Published online1 May 2002Published inissue 1 September 1990https://doi.org/10.1021/ar00177a002RIGHTS & PERMISSIONSArticle Views1012Altmetric-Citations155LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-Alerts Get e-Alerts

ChemInform Abstract: Ketene Chemistry. Part 2. A General Procedure for the Synthesis of 2‐Alkoxycyclopropanecarboxylic Esters and Acids Starting from Aldehydes and Ketenes.

AbstractLewis acid‐catalyzed reaction of the α‐halo acetals (I) with ketene (II) produces the β‐methoxycarboxylates (III) which are cyclized upon treatment with bases, forming the cyclopropane derivatives (IV).

Influence of copper on the chemistry of ketene on ruthenium (001)

Utilisation de la spectroscopie electronique par perte d'energie, a haute resolution, de la thermodesorption et de la spectroscopie electronique Auger

Surface photochemistry. IX. Photochemistry of small molecules on metal surfaces

The chemistry of alkyl halides and ketene has been studied on Pt(111) and on thick layers of Cu on Ru(001). Using postirradiation analysis by high-resolution electron energy-loss spectroscopy and temperature programmed desorption, we have demonstrated the photodissociation of alkyl halides on these two substrates and the alteration of the decomposition channels of ketene. In this paper, we summarize previously reported work and report, for the first time, evidence for photodissociation on copper.

Ketene Chemistry 2.1A General Procedure for the Synthesis of 2-Alkoxycyclopropane-carboxylic Esters and Acids Starting from Aldehydes and Ketene

Ketene Chemistry 2.¹A General Procedure for the Synthesis of 2-Alkoxycyclopropane-carboxylic Esters and Acids Starting from Aldehydes and Ketene

ChemInform Abstract: Chemistry of Transition Metal Ketene Complexes Effective for Useful Utilization of Carbon Monoxide

Transition metal ketene complexes have drawn considerable attention as models for the possible intermediates implicated in the elementary carbon-carbon coupling step in surface-catalyzed or homogeneous carbon monoxide reduction. Although ketene chemistry has been investigated for over 80 years, there have been no review articles on chemistry of transition metal ketene complexes.Three separate aspects of transition metal ketene complexes are reviewed herein, 1) formation of ketene species on catalyst-surface, 2) the preparation and structures of transition metal ketene compexes, 3) chemical properties of transition metal ketene complexes.

Surface chemistry of ketene on ruthenium(001). 2. Surface processes.

The chemistry of ketene (CH/sub 2/CO) on Ru(001) was studied by static secondary ion mass spectrometry (SSIMS) and temperature programmed desorption (TPD). Ketene adsorption at 105 K is both molecular and dissociative and leads to H/sub 2/, CO, and CO/sub 2/, but no hydrocarbons, in TPD. Between 200 and 250 K, molecular ketene is hydrogenated to adsorbed oxygenates, /eta//sup 2/(C,O) acetaldehyde (CH/sub 3/CHO) and /eta//sup 2/(C,O) acetyl (CH/sub 3/CO). The hydrogen is supplied by the decomposition of methylene, the latter produced by ketene decomposition. Hydrogenation to CH/sub 3/CHO is favored at low coverages of ketene, while at high coverages, hydrogenation to CH/sub 3/CO is favored. Pre- or postadsorbed H/sub 2/ enhances the hydrogenation of ketene to CH/sub 3/CHO but does not lead to any hydrocarbon desorption. Between 200 and 250 K, ethylidyne (CCH/sub 3/) forms, particularly at high initial ketene coverages. During dosing at 350 K, ketene decomposes but only H/sub 2/ desorbs. The accumulated adsorbed species include CO and CCH/sub 3/. While dosing at 400 K, both CO and H/sub 2/ desorb, significantly more ketene decomposes than at lower temperatures, and CCH and CH accumulate.

Surface chemistry of ketene on ruthenium(001). 1. Surface structures

Ketene (CH/sub 2/CO) adsorption and reaction on Ru(001) were studied by high-resolution electron energy loss spectroscopy (HREELS), static secondary ion mass spectrometry (SSIMS), and temperature programmed desorption (TPD). Only H/sub 2/, CO, and CO/sub 2/ are observed in TPD. At 105 K, low ketene exposures dissociate to CO and methylene and adsorb molecularly as an /eta//sup 3/(C,C,O) species. At higher exposures ketene adsorbs molecularly as /eta//sup 2/(C,O) acetaldehyde (CH/sub 3/CHO), and /eta//sup 2/(C,O) acetyl (CH/sub 3/CO). Adsorbed acetate is also considered. The hydrogen required for hydrogenation is supplied from decomposition of CH/sub 2/ and ketene. Above 200 K, ethylidyne (CCH/sub 3/) is formed. Methylidyne (CH) and acetylide (CCH) are formed by decomposition of all the above oxygenate and hydrocarbon species. Dosing ketene on Ru(001) at 350 K, where CO accumulates, favors ethylidyne formation. The adsorbed CO stabilizes ethylidyne, which otherwise decomposes at 320 K. Dosing at 400 K, which is above the threshold of CO desorption, results in CH and CCH.

Summary Abstract: The surface chemistry of ketene on Ru(001)

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