Carbonium Ion Rearrangements Research Articles

Total synthesis of (+/-)-dihydrospiniferin-1 via a polyfluoro alkanosulfonyl fluoride induced tandem carbonium ion rearrangement reaction.

A novel polyfluoroalkanosulfonyl fluoride induced carbonium ion rearrangement reaction of gamma-hydroxymethyl cyclohexenone has been used for the total synthesis of (+/-)dihydrospiniferin 1.

Hydrogenolysis of aromatic glycols: an example of multifunctional catalysis by HCo(CO) 4

HCo(CO) 4 catalyzes the hydrogenolysis of diaryl glycols to diarylethanes with very high selectivity at temperatures of 180–220 °C. The reaction pathway was determined by mass spectral identification of intermediate and byproduct molecules and can be rationalized by a multiple-step reaction involving preliminary carbonium ion rearrangement followed by various hydrogenation and homologation reactions. The cobalt catalyzes at least five different types of transformation in order to generate the products observed.

ChemInform Abstract: Carbonium Ion Rearrangements Controlled by the Presence of a Silyl Group.

AbstractTertiary γ‐silylated alcohols such as (I) rearrange in protic acid with 1,2‐shift of R1 (= hydride, phenyl or alkyl) and loss of the silyl group to give the alkenes (II).

Carbonium ion rearrangements controlled by the presence of a silyl group

γ-Silyl tertiary alcohols rearrange in protic acid with 1,2-shift of hydride, phenyl, or alkyl groups, and loss of the silyl group to give alkenes. The placing of the silyl group thus controls the carbonium ion rearrangement in a preparatively useful way. Methoxycarbonyl groups do not migrate; instead, cyclopropanes are formed, except when the conformation suitable for cyclopropane formation is unattainable. When the alkene product is 2,2-disubstituted, it can be reprotonated under the reaction conditions and does not therefore always survive. This can be avoided by carrying out the reaction using a Lewis acid on the silyl ether. The starting γ-silyl alcohols are prepared by a variety of versatile methods.

Bharanginin, a novel heterocyclic [formula omitted]-quinone from pygmacopremna herbacea (Roxb.) moldenke

The structure of bharanginin isolated from the hexane extract of the root nodules of the Ayurvedic drug Pygmacopremna herbacea (Roxb.) Moldenke (Verbenaceae) has been shown to be a novel heterocyclic ortho-quinone (7-isopropyl-3,3,4-trimethylnaphtho[2,3-b]furan-2,5,6(3H)-trione) from a consideration of its high resolution mass spectrum, UV, IR and 1H NMR spectra, long range couplings in its 13C NMR spectrum and one bond Heteronuclear shift correlated 2D NMR spectrum. It appears to be derived biogenetically from ferruginol through the intermediacy of 15-deoxyfuerstione involving a carbonium ion rearrangement and several oxidation steps.

ChemInform Abstract: Novel Cationic Rearrangements of the [3.3.3]Propellane System: Application to the Total Synthesis of Decarboxyquadrone.

AbstractUnter Carboniumionen‐Umlagerung des tetracyclischen Ketons (I) entstehen die ungesättigten Ketone (II) und (III), deren Ringgerüst dem von Quadron (IV) und Isocomen (V) entspricht.

Novel cationic rearrangements of the [3.3.3]propellane system: application to the total synthesis of decarboxyquadrone

The first carbonium ion rearrangement of the [3.3.3]propellane ring system to the tricyclo[4.3.2.01,5]undecane and tricyclo[6.3.0.01,5]undecane skeletons has been observed and extended to the total synthesis of the biologically active compound decarboxyquadrone.

ChemInform Abstract: CARBONIUM ION REARRANGEMENT IN THE SYNTHESIS OF Γ‐LACTONES FROM (E)‐β‐ALKYLCINNAMIC ACIDS

Chemischer InformationsdienstVolume 15, Issue 21 Heterocyclic Compounds ChemInform Abstract: CARBONIUM ION REARRANGEMENT IN THE SYNTHESIS OF Γ-LACTONES FROM (E)-β-ALKYLCINNAMIC ACIDS L. JALANDER, L. JALANDERSearch for more papers by this author L. JALANDER, L. JALANDERSearch for more papers by this author First published: May 22, 1984 https://doi.org/10.1002/chin.198421201Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume15, Issue21May 22, 1984 RelatedInformation

ChemInform Abstract: Stereochemical Evidence for a Carbonium Ion Rearrangement During Reaction of Dimethyltitanium Dichloride with a Ketone.

Racemization during the reaction of dimethyltitanium dichloride with the 2,2-disubstituted cyclopentanone (–)-(3) of high enantiomeric purity provides stereochemical evidence for a carbonium ion rearrangement during this dimethylation process.

Stereochemical evidence for a carbonium ion rearrangement during reaction of dimethyltitanium dichloride with a ketone

Racemization during the reaction of dimethyltitanium dichloride with the 2,2-disubstituted cyclopentanone (–)-(3) of high enantiomeric purity provides stereochemical evidence for a carbonium ion rearrangement during this dimethylation process.

Molecular Mechanics Calculations in Organic Chemistry: Examples of the Usefulness of this Simple Non‐Quantum Mechanical Model

AbstractVarious problems arising in experimental organic chemistry can be clarified by molecular mechanics or force field calculations: molecular dynamics (conformational analysis and internal rotation), the search for the most stable isomer of various polycyclic hydrocarbons, reactivity calculations, including solvolysis of bridgehead substituted systems. Such calculations are shown to be useful in elucidating the mechanism of multistep carbonium ion rearrangement, for predicting the structure and stability of anti‐Bredt olefins, and also offer an explanation for the selectivity observed in the hydrogenolysis of strained polycyclic smallring hydrocarbons, for the identification of long bonds and electronic effects, for the analysis of late transition states, and for the product distribution in complex reactions.

Carbonium ion rearrangements controlled by the presence of a silyl group

Tertiary alcohols with a λ-silyl group ( 3) generally undergo a simple carbonium ion rearrangement in acid giving a single alkene product ( 4) with loss of the silyl group.

Evidence for a carbonium ion rearrangement in the reaction of triisobutylaluminum and 1,3,3-trimethylcyclopropene

Formation of acyclic products in the reaction of triisobutylaluminum and 1,3,3- trimethylcyclopropene can reasonably be ascribed to a carbonium ion rearrangement. This suggestion supports the mechanism for carbalumination of alkenes proposed by Eisch.

ChemInform Abstract: CARBONIUM ION REARRANGEMENTS

Chemischer InformationsdienstVolume 11, Issue 42 Reviews ChemInform Abstract: CARBONIUM ION REARRANGEMENTS V. G. SHUBIN, V. G. SHUBINSearch for more papers by this author V. G. SHUBIN, V. G. SHUBINSearch for more papers by this author First published: October 21, 1980 https://doi.org/10.1002/chin.198042348AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue42October 21, 1980 RelatedInformation

Direction of carbonium ion rearrangements during acylation of propyne by stereoisomers of 4-tert-butyl-1-methylcyclohexanoylcarbonyl cation

A stereospecific migration of the axial substituent (either methyl or acyl group) from the geminal node was discovered when propyne is acylated with the cis- and trans-4-tert-butyl-1-methylcyclohexanoylcarbonyl cations.

ChemInform Abstract: PHOTOREACTIONS OF α‐SULFONYLOXYKETONES

AbstractDie Tosyloxyketone (I), (IX), (XII) und (XV) (dargestellt in 5 l ‐66proz. Ausb. aus den entsprechenden Säurechloriden über die Diazoketone (Ausb. 76‐88%)) gehen bei der Photolyse in Abhängigkeit vom Lösungsmittel Umlagerungen, intramolekulare Cyclisierungen und Lösungsmitteleinfang‐ Reaktionen ein.

Computer predicts organic reaction products

A computer program has been developed that predicts products of organic reactions from starting materials and conditions, using general principles of organic reaction mechanisms. Organic chemistry professor William L. Jorgensen of Purdue University, West Lafayette, Ind., has completed the phase of program development dealing with base-catalyzed and nucleophilic reactions [ J. Org. Chem ., 45 , 2043 (1980)]. Future program modules will include acidcatalyzed and electrophilic, radical, carbene, thermal pericyclic, and photochemical reactions. Such mechanistically oriented programs may permit prediction of undiscovered reactions. Also, proposed reactions can be evaluated for feasibility and competition from side reactions. The ordering of organic mechanistic principles for the program may also improve the teaching of organic chemistry. Other workers have devised mechanistically based programs for such projects as finding the best mechanism for successive carbonium ion rearrangements from starting materials t...

Photoreactions of α-sulfonyloxyketones

Earlier work on the photochemistry of α-sulfonyloxyketones uncovered their propensity to form the corresponding α-keto carbonium ions on photolysis. Typical reactions such as intramolecular cyclizations, carbonium ion rearrangements, and solvent trapping were found. This paper describes an attempt to extend this reaction to a general synthetic technique for polyene cyclizations. During the course of this work two other major reaction pathways were found. The first is an α-keto carbonium ion to acylium ion rearrangement and the second is a photoreduction–elimination process that leads to an α-keto radical rather than the corresponding cation.

Cubyl caged systems: a paradigm of tandem cyclobutylcyclopropylcarbinyl carbonium ion rearrangements

A novel and general carbonium ion rearrangement of homocubanone to tetracyclo(3.3.0.0 2,8.0 3,6)octyl system is reported.

Cubanes uncaged: novel carbonium ion rearrangements of pentacyclo[4.3.0.02,5.03,8.04,7]nonan-9-ones (homocubanones) to bicyclo[3.2.1]octa-2,6-diene and tetracyclo[3.3.0.02,6.03,8]octane ring systems

Several new and unprecedented carbonium ion rearrangements of the cubyl system are reported.