Cyclopropylcarbinyl Cation Research Articles

ChemInform Abstract: Long‐Lived Cyclopropylcarbinyl Cations

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BF 3-induced rearrangement of aziridinocyclopropanes derived from 2-phenylsulfonyl-1,3-dienes. A new approach to the tropane alkaloid skeleton

Five N-substituted derivatives of 1,2-methylene-3,4-aziridino 2-phenylsulfonyl cycloalkanes ( 3a-e) were prepared from their corresponding epoxy cyclopropanes via ring opening of the epoxide by sodium azide and subsequent triphenylphosphine induced cyclization. BF 3-induced reaction of compounds 3a-e resulted in a rearrangement via a cyclopropyl carbinyl cation intermediate. In the case of tosylaziridine 3c bicyclic product 5, (tropane skeleton), was formed as the major product. With carbamate derivative 3a exclusive rearrangement to fluorocyloheptene 7 took place.

Theoretical Characterization of Cycloaddition Reactions of the Cyclopropylcarbinyl Cation

Theoretical Characterization of Cycloaddition Reactions of the Cyclopropylcarbinyl Cation

Substituent effects on cyclobutyl and cyclopropylcarbinyl cations

The acetolyses of 3-substituted cyclobutyl tosylates (X=Ar, Cl, and OEt) were examined giving rate and product distributions. With the alkyl- and aryl-substituted compounds, the rate-determining step leads to the formation of a bridged cyclobutyl cation which then rearranges to a cyclopropylcarbinyl/homoallyl ion. The value of ρ for the solvolysis of the 3-aryl derivatives was -1.5, suggesting some charge transfer to the 3-position. The 3-chlorocyclobutyl tosylates react to give only the inverted 3-chlorocyclobutyl acetates. The 3-ethoxy derivatives give ∼1:1 mixtures of the corresponding acetates. Further information concerning these reactions was obtained via ab initio MO calculations at the MP2/6-31 * theoretical level

Thermolytic rearrangements of 1,1-cyclopropanedimethanol disulfonates: cyclopropylcarbinyl cations revisited

1,1-Cyclopropanedimethanol dimethanesulfonate (1a) and the corresponding ditosylate 1b underwent thermal rearrangement at 110-140 o C after melting. Short reaction time resulted in the formation of mixtures containing 1-(sulfonyloxy)cyclobutanemethanol sulfonates 5a,b (major), starting material, and 2-methylene-1,4-butanediol disulfonates 6a,b. Longerreaction times afforded complex conversion to disulfonates 6a,b, isolated in 49 and 62% yield, respectively. These reactions are postulated to proceed via initial carbocation formation, presumably interconverting bicylobutonium and cyclopropylcarbinyl cations, which exist as ion pairs in the melt

Assignment of Configuration by Mitsonobu Reaction in the 13α-Methylgonane Series

Abstract 17-Ketosteroids in the 13α-methyl-gon-9(11)-ene series almost exclusively undergo nucleophilic attack from the α-face. Intramolecular capture of a cyclopropyl carbinyl cation, generated under Mitsunobu conditions unequivocally confirms the stereochemical course.

Long-lived cyclopropylcarbinyl cations

1 Introduction 2 General Methods of Preparation of Long-Lived Cyclopropylcarbinyl Cations 3 Primary Cyclopropylcarbinyl Cations 4 Secondary and Tertiary Cyclopropylcarbinyl Cations 5 Spirocyclopropylcarbinyl Cations 6 Cyclopropylcarbinyl Dications 7 Extent of Positive Charge Delocalization into the Cyclopropyl Group 8 X-Ray Crystallographic Studies 9 Conclusions and Outlook Keywords: long-lived cyclopropylcarbinyl cations; primary cyclopropylcarbinyl cations; alcohol or halide ionization; hydride ion abstraction from hydrocarbons; secondary and tertiary cyclopropylcarbinyl cations; allyl substituted cyclopropylcarbinyl cations

The structure of cyclopropylcarbinyl cations: the crystal structures of protonated cyclopropyl ketones

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe structure of cyclopropylcarbinyl cations: the crystal structures of protonated cyclopropyl ketonesRonald F. Childs, Marianne D. Kostyk, Colin J. L. Lock, and Mailvaganam MahendranCite this: J. Am. Chem. Soc. 1990, 112, 24, 8912–8920Publication Date (Print):November 1, 1990Publication History Published online1 May 2002Published inissue 1 November 1990https://doi.org/10.1021/ja00180a041RIGHTS & PERMISSIONSArticle Views236Altmetric-Citations30LEARN 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 (1007 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

A photoionization study of [C4H7]+ ions in the gas phase

The ionization and [C4H7]+ appearance energies for a series of C4H7CI and C4H7Br isomers have been measured by dissociative photoionization mass spectrometry. Cationic heats of formation, based on the stationary electron convention, are derived. No threshold ion is observed with a heat of formation corresponding to the trans-1-methylallyl cation, although there is evidence for formation of the less stable cis isomer. A 298 K heat of formation of 871 kJ mol−1 is obtained for the cyclopropylcarbinyl cation, with the cyclobutyl cation having a higher value of 886 kJ mol−1. At the HF/6-31G** level, ab initio molecular orbital calculations show the 2-butenyl, isobutenyl and homoallyl cations to be stable forms of [C4H7]+, being less stable than the trans-1-methylallyl cation by 101 kJ mol−1, 159 kJ mol−1 and 164 kJ mol−1, respectively. However, threshold formation is not observed for any of these ions, the fragmentation of appropriate precursor molecules producing [C4H7]+ ions with lower energy structures.

The C4H7+ cation. A theoretical investigation.

The potential energy surface of the C4H7+ cation has been investigated with ab initio quantum chemical theory. Extended basis set calculations, including electronic correlation, show that cyclobutyl and cyclopropylcarbinyl cation are equally stable isomers. The saddle point connecting these isomers lies 0.6 kcal/mol above the minima. The global C4H7+ minimum corresponds to the 1-methylallyl cation, which is 9.0 kcal/mol more stable than the cyclobutyl and the cyclopropylcarbinyl cation and 9.5 kcal/mol below the 2-methylallyl cation. These results are in excellent agreement with experimental data.

Direct demonstration of the isomerization component of the monoterpene cyclase reaction using a cyclopropylcarbinyl pyrophosphate substrate analog.

The tightly coupled nature of the reaction sequence catalyzed by monoterpene cyclases has precluded direct observation of the topologically required isomerization step leading from geranyl pyrophosphate to the presumptive, enzyme-bound, tertiary allylic intermediate linalyl pyrophosphate, which ultimately cyclizes to the various monoterpene skeletons. By using a partially purified monoterpene cyclase preparation and 2,3-cyclopropylgeranyl pyrophosphate, a substrate analog designed to uncouple the reaction sequence, the production of the corresponding tertiary homoallylic pyrophosphate isomer was demonstrated. This provides direct evidence for the usually cryptic isomerase component of the overall catalytic cycle. A number of other related products generated by reaction of cyclase with the analog were also identified, the structures and proportions of which were consistent with the intermediacy in catalysis of a cyclopropylcarbinyl cation X pyrophosphate anion pair. Kinetic parameters for the analog were compared with those of the natural substrate geranyl pyrophosphate. The results presented confirm mechanistic similarities in the enzymatic ionization and subsequent transformation of allylic pyrophosphate and cyclopropylcarbinyl pyrophosphate intermediates of isoprenoid metabolism.

Effect of polarization functions and electron correlation on the cyclopropylcarbinyl cation and bicyclobutonium ion (C4H7+) potential energy surface

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of polarization functions and electron correlation on the cyclopropylcarbinyl cation and bicyclobutonium ion (C4H7+) potential energy surfaceMichael L. McKeeCite this: J. Phys. Chem. 1986, 90, 21, 4908–4910Publication Date (Print):October 1, 1986Publication History Published online1 May 2002Published inissue 1 October 1986https://doi.org/10.1021/j100412a004RIGHTS & PERMISSIONSArticle Views52Altmetric-Citations16LEARN 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 (342 KB) Get e-Alerts

Structures of two cyclopropylcarbinyl cations

Etude par diffraction RX des structures cristallines des 2 composes [(C 3 H 5 C(OH)C 6 H 5 ] SbF 6 et [(C 3 H 5 ) 2 C(OH)] SbF 6

Structure, energetics and homoaromaticity

Abstract

The 9-barbaralyl cation, 1,4-bishomotropylium ion and some related C 9H 9+ carbocations : Electronic structures, stability and reactivity

The electronic structures of the 9-barbaralyl cation( 1), the 1,4-bishomotropylium ion ( 5) and some related C 9H 9 + isomers have been studied by ab initio STO-3G calculations. The stability of the cyclopropylcarbinyl cation 1 and the homoaromatic ion 5 as compared with their allylic counterparts is explained in terms of delocalization and MO interactions between molecular fragments. Both the symmetry of, and the distance between, molecular fragments are of importance for the electronic structure, and even symmetry-allowed interactions are negligible in the absence of favourable geometrical distortions. The non-classical ion 3 with D 3h symmetry presents special problems where other factors, such as strain, are important for the total energy. A choice between proposed mechanisms for the degenerate rearrangements of 1 can now be made with confidence.

A nonelectrocyclic path from the cyclobutene cation radical to the 1,3‐butadiene cation radical

AbstractThe conversion of the cyclobutene cation radical to the 1,3‐butadiene cation radical has been studied using MINDO/3 and ab initio SCF MO methods. Not only smooth electrocyclic but also stepwise, non‐electrocyclic routes were considered. Both calculational methods agree that the preferred reaction path is a novel nonelectrocyclic one proceeding through an intermediate “cyclopropylcarbinyl cation radical.” The quantitative agreement in the activation parameters calculated by the two methods is excellent. The proposed intermediate also provides an attractive explanation for the mass spectrometric fragmentation patterns of the cyclobutene and butadiene cation radicals.

Silicon-substituted cyclopropylcarbinyl cations

Silicon-substituted cyclopropylcarbinyl cations

The Solvomercuration, Bromination, and Related Reactions of 1,5-Dimethyl-6-methylenetricyclo[3.2.1.02,7]oct-3-en-8-one and Its Related Compounds

Abstract The solvomercuration-demercuration reactions of 1,5-dimethyl-6-methylenetricyclo[3.2.1.02,7]oct-3-en-8-one (1), its corresponding alcohol, and 5,8-dimethyl-9-methylenetricyclo[3.3.1.02,8]non-3-en-7-one (2) were investigated. In all cases, the solvent was stereospecifically incorporated on the exomethylene group, and the original tricyclic skeleton did not undergo rearrangement. Similarly, 1 and 2 underwent a stereospecific bromination on the exomethylene group by means of the reaction with pyridinium tribromide. These results suggest the stabilization of the formal cyclopropylcarbinyl cation intermediates by the adjacent acetoxymercury moiety or the bromine atom. On the other hand, the reaction of NBS–MeOH or NBS–H2O with 1 afforded an addition product on the exomethylene group, and 1,4-addition originated from the cleavage of the cyclopropane ring, while with 2 the reaction afforded only an addition product on the exomethylene group. The difference in this reaction mode is discussed on the basis of the solvent effect and the ring strain of 1.

Synthesis and electrophilic reactions of a conformationally rigid cyclopropylcarbinyl cation. An unusual synthesis of substituted benz[a]azulenes.

A tropylium-substituted cyclopropane has been prepared which is rigidly held in the “bisected” conformation. Its electrophilic reactions are also investigated.

The rearrangement of a tricyclic C 8H 11+ alkyl carbocation into a primary cyclopropylcarbinyl cation

The first unambiguous observation of a “bisected” primary cyclopropylcarbinyl cation is reported. This cation was formed by ring contraction of a C 8 tricyclic framework. Although totally unexpected from a bond energy-steric strain standpoint, this observation underlines the large resonance stability associated uith “bisected” cyclopropylcarbinyl cations.