Cyclopropane Intermediates Research Articles

The Reaction of 1-Amino-2,3-diphenylcyclopropenium Ions with 1,3-Diketones to Afford 2,4-Cyclopentadien-1-ols: The Regioselective Ring-Opening of 1-Aminocyclopropene Intermediates

Abstract 1-Amino-2,3-diphenylcyclopropenium tetrafluoroborates (4) reacted with cyclic or acyclic 1,3-dicarbonyl derivatives (5) such as 1,3-diketones, β-keto esters, or gem-diesters in the presence of triethylamine to give 2,4-cyclopentadien-1-ols in moderate to good yields. Some isolated cyclopropene intermediates were, upon heating, converted to the corresponding cyclopentadienols. The factors that influence on the reactivities of 4 and 5 (basicities of the amino groups of 4 and bulkiness of the substituents of 4 and 5) are discussed qualitatively.

Corner attack on cyclopropane by deuteron and mercuric ions: an example of stereospecific formation and capture of unsymmetrical corner-deuterated/mercurated cyclopropane intermediates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCorner attack on cyclopropane by deuteron and mercuric ions: an example of stereospecific formation and capture of unsymmetrical corner-deuterated/mercurated cyclopropane intermediatesJames M. Coxon, Peter J. Steel, Barry I. Whittington, and Merle A. BattisteCite this: J. Am. Chem. Soc. 1988, 110, 9, 2988–2990Publication Date (Print):April 27, 1988Publication History Published online1 May 2002Published inissue 27 April 1988https://doi.org/10.1021/ja00217a059RIGHTS & PERMISSIONSArticle Views146Altmetric-Citations17LEARN 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 (447 KB) Get e-Alerts Get e-Alerts

Carbon-13 labelling study of the coenzyme B12-dependent methylitaconate ⇌α-methyleneglutarate model rearrangement reaction and examination of potential cyclopropane intermediates

The model rearrangement mimicking the coenzyme B12-dependent, enzyme-catalysed interconversion of α-methyleneglutaric acid with methlitaconic acid has been carried out with a carbon-13 label. This experiment demonstrates beyond doubt that the acrylate group is the migrating group in the model, as it is in the enzyme-catalysed rearrangement. Experiments designed to probe the possible occurrence of cyclopropylmethyl intermediates in the model rearrangement are also described. To this end the cis- and trans-bromomethylcyclopropanediacids (16a) and (20a) were prepared starting from the common precursor cyclopropane-1,1,2-tricarboxylic acid (13). Thus, (13) was converted into the anhydride (14) which was, in turn, reduced to the lactone (15). Opening of the lactone with HBr in acetic acid gave the desired trans-diacid (16a). For the cis-diacid (20a), the anhydride (14) was hydrolysed, esterified with diazomethane, then reduced with lithium triethylborohydride. Conversion of the resulting alcohol (19) into the bromide (20a) was effected with phosphorus tribromide. An extensive series of experiments involving treatment of the acids and their methyl and tetrahydropyranyl esters with vitamin B12S was carried out. No methylitaconic acid (3a) could be detected in any of the reaction mixtures. However, α-methyleneglutaric acid (2a) and methylglutaconic acid (21) were observed as the reaction products. The methyl toluene-p-sulphonate (22) and iodide (23) were also examined and yielded results analogous to those obtained with the bromides.

ChemInform Abstract: Stereospecific Synthesis of cis‐Pyrethroids by the Cyclopropene Route Using a Carbanionic Synthon. Part 2. Approach to cis‐Chrysanthemic and cis‐Pyrethric Derivatives.

AbstractThe pyrazoles (I), whose synthesis is described in the preceding paper, are photolyzed to give cyclopropene intermediates.

ChemInform Abstract: Synthesis of Cycloalkenones via the Intramolecular Cyclopropanation of Furanyl Diazo Ketones.

AbstractTreatment of the furanyl‐ and benzofuranylethyl diazoketones (I), (III), (VII), and (X) with rhodium(II) acetate leads to the formation of cyclopropane intermediates which, in the case of (IV) and (XI), be isolated.

ChemInform Abstract: MINDO/3 Study of the Isomerization of 1‐Methylcyclohexylium Ion to 1‐Ethylcyclopentylium Ion. An Alternative Mechanism for This Branching Rearrangement.

A MINDO/3 study of the rearrangement mechanism of 1-methylcyclohexylium ion to 1-ethylcyclopentylium ion is presented. The structures at three intermediates and three transition states have been calculated and characterized. The results show that a ring-contraction mechanism via a corner-protonated cyclopropane intermediate is a more adequate description of this process than one based on an H-bridged edge-protonated cyclopropane intermediate. The value calculated for the barrier height for the ring-expansion process (14.5 kcal mol–1) is in good agreement with the experimental value (15.4 kcal mol–1) for the activation energy. The proposed mechanism resembles the Wagner–Meerwein ring-contraction reaction.

MINDO/3 study of the isomerization of 1-methylcyclohexylium ion to 1-ethylcyclopentylium ion. An alternative mechanism for this branching rearrangement

A MINDO/3 study of the rearrangement mechanism of 1-methylcyclohexylium ion to 1-ethylcyclopentylium ion is presented. The structures at three intermediates and three transition states have been calculated and characterized. The results show that a ring-contraction mechanism via a corner-protonated cyclopropane intermediate is a more adequate description of this process than one based on an H-bridged edge-protonated cyclopropane intermediate. The value calculated for the barrier height for the ring-expansion process (14.5 kcal mol–1) is in good agreement with the experimental value (15.4 kcal mol–1) for the activation energy. The proposed mechanism resembles the Wagner–Meerwein ring-contraction reaction.

Force field-SCF calculations on cyclopropene intermediates in carbene rearrangements. Comparison with experiment

Heats of formation and geometries of benzocyclopropene, cyclopropa[ b]naphthalene, bicyclo[4.1.0]hepta-2,4,7-triene, and benzannelated derivatives have been calculated with a combined force field-SCF program. The bicycloheptatrienes are stabilized relative to the isomeric arylcarbenes by benzannelation, and destabilized by loss of aromaticity and/or increased strain. 1-Naphthylcarbene, 2-naphthylcarbene, 9-phenanthrylcarbene and 9-anthrylcarbene were generated by gas-phase pyrolysis of the corresponding arene aldehyde tosylhydrazone sodium salts, diazomethanes, or 5-aryltetrazoles, and rearranged to cyclobuta[ de]naphthalene ( 21), cyclobuta[ jk]phenanthrene ( 33), and cyclobuta[ de] anthracene ( 38), respectively. 10,11-Dihydrodibenzo[ ad]cyclohepten-5-ylidene ( 15), similarly generated from 5-diazo-10,11-dihydro-5H-dibenzo [ ad]cycloheptene( 39), rearranged to 5a,9b-dihydro-5 H-benzo[3,4]cyclobut[1,2-a] indene( 40), 5 H-dibenzo[ ad]cycloheptene( 41), and 8,9-dihydro-4 H-cyclopenta[ def]phenanthrene( 44). 40 rearranged thermally to 41. The mechanisms of the rearrangements are discussed.

Alternative mechanisms for cyanide anion exchange with acetonitrile

Mechanisms for the recently observed exchange of cyanide anion in acetonitrile have been investigated by means of semi-empirical MNDO molecular orbital calculations. A prototropic type mechanism via a cyclopropane intermediate is the most likely candidate. The previously proposed concerted migration is indicated to be the least favourable reaction pathway.

Aza- and oxa-eburnamonine : Reactions with indole derivatives, part XLVII

Ring opening reactions of cyclopropane intermediates give rise to pentacyclic eburnamonines with a nitrogen or oxygen atom at position 15.

Competitive 1,2- and 1,3-hydride shifts and the possible role of protonated and methylated cyclopropane intermediates in alkyl group rearrangements accompanying the thermal decomposition of saturated alkyl chloroformates in the liquid phase

Deuterium labelling shows that the thermal decomposition of ethyl chloroformate in the liquid phase yields chloroethane without rearrangement of the ethyl group. Longer chain primary alkyl chloroformates yield rearrangement products which can be rationalised on the basis of two initial competitive pathways, one involving a 1,2-hydride shift and the other the formation of a corner-protonated cyclopropane intermediate. The latter may be captured to yield rearranged primary alkyl chloride (with considerable proton scrambling in the n-propyl case) or give rise to a 1,3-hydride shift in higher alkyl groups (Bun, n-pentyl, 3-methylbutyl, n-octyl) where rearrangement to a s- or t-alkyl cation is possible. Successive 1,2-hydride shifts are of minor significance unless the second of these leads to a t-alkyl cation. The 3,3-dimethylbutyl group affords products derived from successive 1,2-shifts of hydrogen and methyl and also a 1,2-t-butyl shift which is thought to involve the intermediacy of a methylated cyclopropane. s-Alkyl cations derived directly from s-alkyl chloroformates show less tendency to rearrangement than those derived by rearrangement from primary alkyl chloroformates. Evidence is presented which suggests that alk-1-enes are formed from primary alkyl chloroformates via carbocation intermediates in which rearrangement by 1,2- and/or 1,3-hydride shift has occurred.

An ICR study of the reactions of CH 5+ and C 2H 5+ with n-hexane labelled with 13C

The reactions occurring in the chemical ionization (CI) of n-hexane with methane as reagent gas have been studied in an ion cyclotron resonance mass spectrometer. Extensive use of 13C-labelled reactants was made. The results obtained substantiate the different modes of reaction of the two major reactant ions in methane, viz. CH 5 + acts as a proton donor to form an hexonium ion intermediate and C 2H 5 + acts as an hydride acceptor to form an hexyl ion. The decomposition of the latter ion is discussed in terms of rearrangement steps involving the formation of substituted protonated cyclopropane intermediates. An approximate value of 4 · 0 8 s −1 is suggested for the migration frequency of hydrogen atoms in the rearrangement process. Analytical application of CI(CH 4) is also considered.

ChemInform Abstract: THE CHEMISTRY OF SMALL‐RING COMPOUNDS. PART 39. DISPLACEMENTS IN CYCLOPROPYL CHLORIDES ACTIVATED BY ELECTRON‐DONATING SUBSTITUENTS

AbstractDas Chlorid (Ia) geht bei ‐30 °Cmit Methanol über das Ion (IIa) in den Diether (IIIa) über.

The reaction of some dibromocyclohexanediones with bases

The reaction of some dibromocyclohexanediones with bases is reported. Elimination of HBr, believed to proceed via cyclopropane intermediates, yields ultimately cyclopentenediones. A possible mechanism is described.

Reaction of nortricyclene with deuteriotrifluoroacetic acid. Evidence for the formation of edge-protonated cyclopropane intermediate

Reaction of nortricyclene with deuteriotrifluoroacetic acid. Evidence for the formation of edge-protonated cyclopropane intermediate

The chemistry of small‐ring compounds. Part 39. Displacements in cyclopropyl chlorides activated by electron‐donating substituents

AbstractCyclopropyl chlorides with a methoxy‐ or a p‐tolyl group linked to the same carbon atom as halogen undergo substitutions in polar solvents with relatively little ring rupture, when the nucleophile is sufficiently reactive (e.g. methanol, N−3, Br−) to trap the intermediate α‐substituted cyclopropyl cations.Such substitution reactions are of the SN1 type and do not proceed via cyclopropene intermediates. With poor nucleophiles such as NO−3 in aqueous acetone, only polymeric ring‐opened products are formed.

Protonated cyclopropane intermediates from the deamination of 3-methyl-2-aminobutane

Protonated cyclopropane intermediates from the deamination of 3-methyl-2-aminobutane

Evidence for cyclopropene intermediates in the rearrangement of aromatic carbenes to arylcarbenes

Evidence for cyclopropene intermediates in the rearrangement of aromatic carbenes to arylcarbenes

One-stage double methylene transfer reactions from methylsulphinylmethanide to activated double bonds. Mimetic of in vivo C-ethylation

One-stage sequential double methylations of the CC bonds in stilbene, 2-methylstilbene, and 4,4′-dimethoxystilbene from methylsulphinylmethanide (DMSO–) leading to methyl diarylbutyl sulphoxides [e.g.(3) and (14)] are described. The same methyl diarylbutyl sulphoxides are produced when the corresponding α-methylstilbenes [e.g.(6)] or, in one case, the corresponding styrene (5) and lower homologous sulphoxide (4) are similarly treated with DMSO–; the double methylene transfer process follows according to Scheme 2. Thermal elimination of methanesulphenic acid from the sulphoxides (3) and (14) produces 3,4-diarylbut-1-enes, which are smoothly isomerised by DMSO– to a mixture of Z- and E-isomers of α-ethylstilbenes and α-benzyl-β-methylstyrenes. Cyclopropane intermediates are shown not to be implicated in any of the reaction schemes by the observation that authentic trans-1,2-diphenylcyclopropane is recovered unchanged after treatment with DMSO–; the corresponding cis-cyclopropane is quantitatively converted into the trans-isomer in DMSO––DMSO. (E)-Stilbene reacts with the anion produced from diethyl sulphoxide and sodium hydride to give a mixture of Z- and E-isomers of α-ethylstilbene and α-benzyl-β-methylstyrene. The relationship between this work and in vivo C-ethylation from L-methionine is discussed.

Reactions of 5α-hydroxy-steroids: the mechanism of backbone rearrangement in sulphuric acid–acetic acid–acetic anhydride

Reaction of 4β-acetoxy-5α-hydroxycholestane (4) with D2SO4–DOAc–Ac2O gives the acetoxy-olefins (5)–(7) with no incorporation of deuterium; these observations exclude the intermediacy of olefin and cyclopropane intermediates in the backbone or partial backbone rearrangement.