Showing papers on "Cyclopropane published in 1985"
TL;DR: In this article, the relationship between 3-membered rings and a-complexes is demonstrated by analyzing their electron density pattern with the aid of catastrophe theory, and the bend of the 3-MR bonds is described by the curvature of the paths of maximum electron density linking the ring atoms.
Abstract: Energy, geometry, one-electron density distribution, and Laplace concentrations of cyclopropane (l), aziridine (2), oxirane (3), cyclopropyl anion (4), protonated aziridine (5), protonated oxirane (6), halogen-bridged fluoroethyl cation (7), and hydrogen-bridged ethyl cation (8) are investigated and compared with their corresponding alicyclic counterparts. The relationship between three-membered rings (3MR) and a-complexes is demonstrated by analyzing their electron density pattern with the aid of catastrophe theory. A continuous change from 3MRs to .rr-complexes can be observed if the acceptor (donor) ability of a group X interacting with an ethylene unit is increased (decreased). The bend of the 3MR bonds is described by the curvature of the paths of maximum electron density linking the ring atoms. Interpath angles are used to evaluate the strain energy of a 3MR. A value of 75 kcal/mol is found for 1. Strain is partially compensated by stabilizing effects arising from surface delocalization of cr-electrons of the 3MR (48 kcal/mol for 1). Both ring strain and surface delocalization increase in the series 1, 2, 3 with a slight dominance of the former effect. The chemical relevance of theoretical results is discussed with regard to the ability of 3MRs to interact with mystems and to undergo addition reactions with electrophiles and nucleophiles. The observed regioselectivity in ring-opening reactions of oxiranes is explained.
203 citations
TL;DR: Observations are consistent with the poor packing ability of mixed saturated and cyclopropane-containing chains due to the bulky substituent effect.
Abstract: The thermotropic behavior and molecular properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-dihydrosterculoyl-sn-glycero-3-phosphoethanolamine (PDSPE) have been investigated by 2H NMR spectroscopy using samples selectively labeled at the 5'-, 9'-, 10'-, and 16'-positions of the sn-2 chains. Comparison with the corresponding phosphocholine analogues (POPC and PDSPC), obtained as intermediate synthetic products, was used to monitor the role of the polar head group. Replacement of the choline moiety by ethanolamine increased the gel to liquid-crystal transition temperature by 10-32 degrees C and led to a significantly higher ordering of the fatty acyl chains in the liquid-crystalline bilayer state. The lateral compression effect, due to the smaller area per polar head group in PE, results in a bilayer to hexagonal phase transition at elevated temperatures. The effects on both PC and PE due to replacement of the olefinic group by a cyclopropane unit are similar. A decrease in the temperature of the gel to liquid-crystal phase transition, Tc, is observed upon introduction of a cyclopropane ring; it goes from 26 degrees C in POPE to approximately 10 degrees C in PDSPE. In addition, a very significant broadening of the transition profile is observed. These observations are consistent with the poor packing ability of mixed saturated and cyclopropane-containing chains due to the bulky substituent effect. The temperature of the bilayer-hexagonal phase transition of PE samples was decreased by 15-20 degrees C on replacement of oleoyl chains by dihydrosterculoyl chains at the sn-2 position.(ABSTRACT TRUNCATED AT 250 WORDS)
79 citations
61 citations
TL;DR: In this paper, the authors studied the electronic structure of CI2Ti(C2H4) and found wave functions describing both the metalla-cyclopropane and a-complex forms.
Abstract: We have studied the electronic structure of CI2Ti(C2H4) and found wave functions describing both the metalla- cyclopropane and a-complex forms The metallacyclopropane form is lower in energy than the a-complex form at all geometries we investigated We show that the three-membered ring is strained and that simple 2, + 2, reactions of the Ti-C bonds can relieve this strain The ability of the metallacycle to undergo these pericyclic reactions sets it apart from the simple acid-base a-complex
58 citations
TL;DR: Prepar chauffage, ce complexe est transforme en p-tolyl-1 oxa-2 bicyclo [3.1.0] hexane as mentioned in this paper, mise en evidence d'un intermediaire
52 citations
TL;DR: Picolinyl esters have been recently introduced for the mass spectrometric structure determination of unsaturated and cyclopropane fatty acids and there was no interspecific variation in the position of unsatu‐ration or methylene bridges, even in the recently discovered gastric Campylobacter like organisms (GCLO) or the urease positive thermophilic campylobacters (UPTC).
Abstract: Picolinyl esters have been recently introduced for the mass spectrometric structure determination of unsaturated and cyclopropane fatty acids. We have used these derivatives to characterize the unsaturated and cyclopropane acids of Campylobacter species. The principle unsaturated acids were shown to be 11-octadecenoic acid, with smaller amounts of 9-hexadecenoic acid, 9-octadecenoic acid and 9, 11-octadecadienoic acid. The only cyclopropane acid present was cis 11, 12-methylene octadecanoic acid. There was no interspecific variation in the position of unsatu-ration or methylene bridges, even in the recently discovered gastric Campylobacter like organisms (GCLO) or the urease positive thermophilic Campylobacters (UPTC), the fatty acid profiles of which were consistent with their inclusion in the genus Campylobacter.
49 citations
TL;DR: In this article, the treatment of cis -1-iodo-3-chloro-1-propene derivatives, readily obtainable via trans addition of organometals to propargyl alcohols followed by iodinolysis and chlorination, with alkyllithiums, such as t -BuLi and n-BuLi, can proceed rapidly and cleanly even at −78°C.
47 citations
TL;DR: The hydrocarbon chain orientational order parameters of membranes of Acholeplasma laidlawii B were determined via fluorine-19 nuclear magnetic resonance spectroscopy over a range of temperatures spanning the corresponding gel to liquid-crystalline phase transitions (determined via differential scanning calorimetry).
Abstract: The hydrocarbon chain orientational order parameters of membranes of Acholeplasma laidlawii B, enriched with large quantities of fatty acids containing either a cis or a trans cyclopropane ring or a cis or trans double bond, plus small quantities of one of an isomeric series of monofluoropalmitic acids, were determined via fluorine-19 nuclear magnetic resonance spectroscopy over a range of temperatures spanning the corresponding gel to liquid-crystalline phase transitions (determined via differential scanning calorimetry). Membrane orientational order profiles in the liquid-crystalline state were generally similar, regardless of the particular fatty acid structure present, showing a region of relatively constant order preceding a region of progressively decreasing order toward the methyl terminus of the acyl chain. In the gel state, the order profiles in the presence of either a trans cyclopropane ring or trans double-bond substituent were similar and were characterized by a pronounced head to tail gradient of order at temperatures just below the lipid phase transition, while at temperatures far below the lipid phase transition this gradient was less pronounced, all chain positions showing a more uniformly high degree of orientational ordering. In the gel state, the order profiles in the presence of either a cis cyclopropane ring or a cis double-bond substituent were also similar but were highly unusual in that order first increased and only then subsequently decreased toward the acyl chain methyl terminus. In addition, the substituents in the cis configuration, whether a cyclopropane ring or a double bond, were overall more disordered in the gel state than the corresponding substituents in the trans configuration.(ABSTRACT TRUNCATED AT 250 WORDS)
45 citations
34 citations
TL;DR: A general approach to study peptide structure is presented using three areas of ongoing research in the authors' laboratories, including the molecular basis for taste of peptide derivatives, and the structural and conformational preferences deduced from spectroscopy and molecular mechanics to biological activity.
Abstract: A general approach to study peptide structure is presented using three areas of ongoing research in our laboratories. The first involves the molecular basis for taste of peptide derivatives. We synthesized dipeptides based on L-aspartyl-α-aminocycloalkane carboxylic acid methyl ester. A homologous series of cycloalkane derivatives was studied. The cyclopropane, cyclobutane, and cyclopentane derivatives are sweet, the cyclohexane and cycloheptane peptides are bitter, and the cyclooctane homolog is tasteless. The related acyclic analog L-aspartyl-aminoisobutyric acid methyl ester is sweet, while the L-aspartyl diethyl glycine carboxylic acid methyl ester is tasteless. A model is presented to explain these experimental observations. The second area involves depsipeptides as isosteric replacements of α-hydroxy acids for amino acid residues in peptide chains. We have synthesized sequentially defined polydepsipeptides as model systems for polypeptides. A detailed analysis of the conformational order for these polydepsipeptides is presented. The third area involves partial retro–inverso peptide modifications of isomeric cyclic enkephalin analogs, which illustrate the relationship between the modification and biological activity. We are probing the intramolecular hydrogen-bonding features for these biologically active molecules. From such findings we are relating the structural and conformational preferences deduced from spectroscopy and molecular mechanics to biological activity.
32 citations
TL;DR: In this paper, a quaternization of vinylidenebis(diphenylphosphane) with CH3I or CH3OSO2F yields the diquaternary salts, whose olefinic double bond is strongly electrophilic through the activation by two geminal phosphonium centres.
Abstract: Die erschopfende Quartarisierung von Vinylidenbis(diphenylphosphan) (1) mit CH3I oder CH3OSO2F liefert Diquartarsalze 2a,b, deren olefinische Doppelbindung durch die beiden Phosphonium-Zentren stark elektrophil aktiviert ist Die Addition von Methanol oder Ethanol an 2a,b liefert entsprechend die β-alkoxysubstituierten Doppelphosphonium-Salze 9a–i Die Struktur eines dieser Produkte (9a: XI, RCH3) wurde durch eine Einkristall-Rontgenbeugungsanalyse gesichert, fur die ubrigen liegen spektroskopische Daten vor – Triphenylphosphoniumcyclopropylid (5) ergibt mit (C6H5)2PCl das geminal phosphinosubstituierte Salz 6, das durch CH3OSO2F zum Bisphosphonium-Salz quartarisiert werden kann (7a,b) Ein symmetrisches Homologes 7 c entsteht aus Cyclopropylidenbis(diphenylphosphan) (8) und CH3OSO2F In 7a–i ist der Cyclopropan-Cyclus ebenfalls deutlich elektrophil aktiviert Mit Alkoholen tritt Ringspaltung ein, die hier zu γ-alkoxylierten Salzen 10a,b fuhrt
Olefin and Cyclopropane Activation Through Geminal Phosphonium Centres
Complete quaternization of vinylidenebis(diphenylphosphane) (1) with CH3I or CH3OSO2F yields the diquaternary salts 2a,b, whose olefinic double bond is strongly electrophilic through the activation by two geminal phosphonium centres Accordingly, addition of methanol or ethanol to 2a,b leads to β-alkoxy-substituted double phosphonium salts 9a–i The structure of one of these products (9a: XI, RCH3) was elucidated by single crystal X-ray diffraction analysis Spectroscopic data are provided for the remaining compounds – Treatment of triphenylphosphonium cyclopropylide (5) with chlorodiphenylphosphane gives the gem-phosphinosubstituted salt 6, which can be quaternized with CH3OSO2F to yield a bis-phosphonium salt (7a,b) A symmetrical homologue 7c is formed from cyclopropylidenebis(diphenylphosphane) (8) and CH3OSO2F In 7a–i the cyclopropane cycle is also clearly activated Ring cleavage occurs with alcohols leading to γ-alkoxylated salts 10a,b
TL;DR: In this article, the metal-carbene reacts with both cyclopropane and cyclobutane by initial C-C bond insertion, and an MC/sub 5/H/sub 6//sup +/ ion is produced which consists of cyclopentadiene bound to the metal ion.
Abstract: Gas-phase reactions of the title carbenes with cyclic alkanes with use of Fourier transform mass spectrometry (FTMS) are described. The metal-carbene reacts with both cyclopropane and cyclobutane by initial C-C bond insertion. The methylidene-metallacyclobutane species produced from cyclopropane appears to decompose by three pathways: (1) cleavage of the metallacyclobutane ring (olefin metathesis), (2) ring expansion by carbene/alkyl coupling, and (3) ..beta..-hydride abstraction. With cyclobutane, an MC/sub 5/H/sub 6//sup +/ ion is produced which consists of cyclopentadiene bound to the metal ion. For cyclopentane and cyclohexane, initial insertion into C-H bonds dominates generating M(cyclic olefin)/sup +/ species. Small amounts of M(C/sub 6/H/sub 8/)/sup +/ and M(C/sub 7/H/sub 8/)/sup +/ were also produced from cyclopentane and cyclohexane, respectively, and are assigned as M(MCP)/sup +/ (MCP = methylcyclopentadiene) and M(tol)/sup +/ (tol = toluene). 62 references, 1 figure, 2 tables.
TL;DR: The hydrogenolysis of propane, butane, isobutane, pentane, cyclopentane, and neohexane was observed to occur at roughly equal rates on Mo(0)Al2O3 as mentioned in this paper.
TL;DR: In this article, the surfaces for cis-trans isomerization and racemization of cyclopropane radical cation (1+) were determined using abinitio calculations.
Abstract: The surfaces for cis–trans isomerization and racemization of the cyclopropane radical cation (1+) are determined using abinitio calculations. It is found that polarization functions and electron co...
TL;DR: The use of transition metal oxidants such as copper(II), permanganate, and ferrate ions gives completely scrambled cis-and trans-[1,2-2H2]ethylene as is found in the biosynthetic process as mentioned in this paper.
Abstract: Whereas hypochlorite oxidation of 1-amino-cis-[2,3-2H2]cyclopropane carboxylic acid yields ethylene with retention of stereochemistry the use of transition metal oxidants, such as copper(II), permanganate, and ferrate ions gives completely scrambled cis- and trans-[1,2-2H2]ethylene as is found in the biosynthetic process.
TL;DR: In this article, the parent, cyclic structure for the cyclopropane radical cation undergoes ring opening in a CFCl 2 CF 2 Cl matrix, and the derived species has a SOMO localised on only one of the terminal CH 2 groups.
TL;DR: In this article, quelques transformations of (+)-carene-2 via reactions de chloro-and oxypalladation are described via the reactions of chloro and oxypanadation.
TL;DR: In this article, the effects of the amine group as a substitute in several strained systems: cyclopropane, triprismane, and cubane, were investigated and shown to be reactive sites toward electrophilic attack.
Abstract: : The bond-deviation index and the electrostatic potential have been used to study the effects of the amine group as a substitute in several strained systems: cyclopropane, triprismane, and cubane. For the parent hydrocarbons, the bond-deviation index shows triprismane to have both cyclopropane-like and cubane-like C-C bonds, a conclusion that is confirmed by these molecules' electrostatic potentials. In all three hydrocarbons, there are negative electrostatic potentials associated with the C-C bonds, showing these to be reactive sites toward electrophilic attack. The introduction of amine substituents, which we normally find to have pyramidal geometries in these systems, weakens these negative regions. When the NH2 is forced to be coplanar with the carbon to which it is attached, however, it has the effect of strengthening the negative C-C bond potentials. This can be interpreted as involving a pi-type charge donation by the amine group to the carbon framework.
TL;DR: In this article, it was shown that the methylene group adjacent to a cyclopropane ring can be oxidized to the keto group directly with ruthenium tetroxide.
Abstract: A new finding that the methylene group adjacent to a cyclopropane ring can be oxidized to the keto group directly with ruthenium tetroxide is described.
TL;DR: In this article, the reactions of dihalogenocarbenes (CX 2, X = F, Cl, Br) with CF 3 SCH 2 or (CF 3 S) 2 C CH 2 yield the corresponding substituted cyclopropanes.
TL;DR: In this article, the intermediate derived by the addition of tribromomethylanion is trapped by cyclisation at that position to produce a (tribrommethyl)cyclopropane.
TL;DR: In this paper, the highly stereoselective total synthesis of (±)-cycloeudesmol was achieved by the stereodelective cyclopropane ring formation of an epoxy alcohol (7 ) as a key reaction.
TL;DR: In this paper, 2-Lithio-2-phenylsulfonyl propane has been successfully used for cyclopropanation of electrophilic olefins and plays the role of an alkylidene transer reagent.
TL;DR: In this article, the conversion of series of specifically 2-alkylated-3-deuteriated-1-aminocyclopanecarboxylates by apple tissue into mixture of cis-and trans-1deuterioalk-1enes is reported; the results are in accord with a stepwisw enzymatic mechanism of cyclopropane ring opening in which stereochemical equilibration is faster than the subsequent bond breaking process.
Abstract: The conversion of series of specifically 2-alkylated-3-deuteriated-1-aminocyclopanecarboxylates by apple tissue into mixture of cis-and trans-1-deuterioalk-1-enes is reported; the results are in accord with a stepwisw enzymatic mechanism of cyclopropane ring opening in which stereochemical equilibration is faster than the subsequent bond breaking process.
TL;DR: In this paper, the optical yields of cyclopropane derivatives obtained from (−)-dimenthyl and (−-dibornyl fumarate both exhibit maximum values at 23 °C and an approximate general linearity between the highest optical yield and the optical rotation of the chiral fumarates was observed.
TL;DR: The possible existence of an interaction between the ring-opened cyclopropane radical cations and the CFCl 2 CF 2 Cl solvent has been investigated by ESR studies.
TL;DR: In this paper, an alternative method for the synthesis of 4-alkyl-2 (5H)-furanones is described, where α-diazo compounds in the presence of rhodium acetate or copper acetylacetonate furnished the bicyclic compounds.
Abstract: An alternative method for the synthesis of 4-alkyl-2 (5H)-furanones is described. Intramolecular carbene addition reaction of α-diazo compounds (4) in the presence of rhodium acetate or copper acetylacetonate furnished the bicyclic compounds (5), which were subjected to cyclopropane ring-opening reaction to give the 4-alkyl-4, 5-dihydrofuran-2 (3H)-ones (6) regioselectively. These compounds (6) were further converted into 4-alkyl-2 (5H)-furanones (14) in several steps.