Showing papers on "Cyclopropane published in 1972"
TL;DR: In this paper, it was shown that the strained cyclic molecules cyclopropene and cyclopsopropane are preferentially stabilized by the addition of d functions, and the relative energies were given to an accuracy of 3 kcal/mole or better.
955 citations
TL;DR: In this article, the 1H n.m.r. spectra of cyclopropane derivatives were analyzed and the configuration of the derivatives was determined by analysis of 1H-NMR-Spektren bestimmt.
Abstract: Phenyl(methoxy)carben-pentacarbonyl-chrom(0) (1) reagiert bei erhohter Temperatur mit trans-Zimtsaure-methylester (2), Fumar- (3) und Maleinsaure-diathylester (4) unter Ubertragung des Carben-Liganden stereospezifisch zu den entsprechenden Methoxy-phenyl-cyclopropancarbonsaureestern (6–8). Deren Konfiguration wird durch Analyse der 1H-NMR-Spektren bestimmt. Die IR- und Massenspektren der Verbindungen werden diskutiert. Die Umsetzungen der Phenyl(methoxy)carben-pentacarbonyl-Komplexe des Chroms(0) (1), Molybdans(0) (10) und Wolframs(0) (11) mit trans-Crotonsaure-methylester (5) und Maleinsaure-diathylester zeigen einem carbenoiden Ubergangszustand entsprechend eine Abhangigkeit des Produktverhaltnisses der Cyclopropan-Isomeren vom Ubergangsmetall an.
Transition Metal Carbene Complexes, XLII. Synthesis of Cyclopropane Derivatives from α.β-Unsaturated Alkyl Carboxylates with the Aid of Transition Metal Carbonyl Carbene Complexes
[Phenyl(methoxy)carbene]pentacarbonylchromium(0) (1) reacts at elevated temperature with trans-methyl cinnamate (2), diethyl fumarate (3) and diethyl maleate (4) stereospecifically to give the corresponding methyl and diethyl [methoxy(phenyl)cyclopropane]-carboxylates (6–8) by transfer of the carbene ligand. The configuration of the cyclopropane derivatives is determined by analysis of the 1H n.m.r. spectra. The i.r. and mass spectra of the cyclopropane compounds are discussed. The reactions of the [phenyl(methoxy)carbene]pentacarbonyl complexes of chromium(0) (1), molybdenum(0) (10) and tungsten(0) (11) with trans-methyl crotonate (5) and diethyl maleate indicate a dependence of the ratio of the cyclopropane isomers on the transition metal which is consistent with a carbenoid transition state.
112 citations
TL;DR: In this article, the diffusion coefficients in air at 298.2 °K and 1 atm pressure were reported for different types of butane, ethene, ethane, cyclopropane, propene, propadiene and propyne.
Abstract: Diffusion coefficients in air at 298.2 °K and 1 atm pressure are reported for ethane, ethene, ethyne, cyclopropane, propene, propadiene, propyne, butane, 1-butene, 2-methylpropene, cis-2-butene, tr...
58 citations
48 citations
41 citations
40 citations
TL;DR: The structures and absolute configurations of 9-oxo-9,11-secogorgost-5-ene-3β, 11-diol 11-acetate and 23-demethylgorgosterol have been determined by single crystal X-ray diffraction studies on their p-iodobenzoate derivatives as mentioned in this paper.
Abstract: The structures and absolute configurations of 9-oxo-9,11-secogorgost-5-ene-3β,11-diol 11-acetate and 23-demethylgorgosterol have been determined by single crystal X-ray diffraction studies on their p-iodobenzoate derivatives.
38 citations
TL;DR: In this paper, the authors studied the proton-decoupled carbon-13 magnetic resonance spectra of a series of cyclopropane derivatives and proposed simple rules to distinguish stereoisomeric 1,2-disubstiuted cyclopsanes.
Abstract: Proton-decoupled carbon-13 magnetic resonance spectra of a series of cyclopropane derivatives have been studied. For stereoisomeric substituted 2-phenylcyclopropanes a difference between the isomers has been found in the shieldings of the three-membered cyclic carbons as well as in the shieldings of the carbons of the substituents. The chemical shifts have been interpreted on the basis of an additive approach worked out in a study of the spectra of monosubstituted cyclopropanes and substituted 2,2-diphenylcyclopropanes. Some simple rules have been proposed, which are useful in distinguishing stereoisomeric 1,2-disubstiuted cyclopropanes.
38 citations
TL;DR: In this article, the one-electron structure of the valence shell of the P4 molecule has been investigated by means of helium(I) photoelectron spectroscopy.
35 citations
TL;DR: The planar moments of cyclopropyl derivatives studied by microwave spectroscopy indicate a consistent shortening of the C-C bond opposite an unsaturated substituent compared with the corresponding length opposite saturated substituents as mentioned in this paper.
Abstract: Analysis of the planar moments of cyclopropyl derivatives studied by microwave spectroscopy indicates a consistent shortening of the C–C bond opposite an unsaturated substituent compared with the corresponding length opposite saturated substituents.
26 citations
TL;DR: In this paper, the synthesis of three α-cyclopropyl carbonyl compounds of carbohydrate origin, 1, 2, 3, were described, and the sequence leading to 2 (via 8) began with ethyl 4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside, which added methylene to give the α-Dallo configuration with the cyclopropane ring syn to the glycosidic ethoxy group.
Abstract: The syntheses of three α-cyclopropylcarbonyl compounds of carbohydrate origin, 1, 2, 3, are described. The cyclopropyl carboxaldehyde 1 was obtained from the corresponding carbinol by manganese dioxide oxidation of the primary alcohol. However, the secondary cyclopropyl alcohol in 8 did not respond to manganese dioxide and its oxidation (in the tritylated derivative (14), to the cyclopropyl ketone, 2, had to be achieved by ruthenium tetroxide. The sequence leading to 2 (via 8) began with ethyl 4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside 11, which added methylene to give the α-D-allo configuration with the cyclopropane ring syn to the glycosidic ethoxy group. The diastereomeric tritylated cyclopropyl ketone 3, possessing the cyclopropyl ring anti to the ethoxy group, resulted from cyclopropanation of the αβ-un-saturated ketone, 15. In the latter case, the acetoxy group apparently provides greater directing influence to the incoming methylene than does the allylic ethoxy group.
TL;DR: In this article, gas chromatography results showed that methoxylated esters are characterized by intense peaks due to cleavage adjacent to methoxy-functions which allow the position of the ring in the original cyclopropane ester to be easily assigned.
Abstract: Methyl esters of methylcis- andtrans-9,10-methyleneoctadecanoic acids react with 50% boron trifluoride-methanol to produce unsaturated and methoxy-esters; both products are shown by gas chromatography to be a mixture of several isomers. Mass spectra of the methoxylated esters are characterized by intense peaks due to cleavage adjacent to methoxy-functions which allow the position of the ring in the original cyclopropane ester to be easily assigned. Methyl oleate is also partially attacked by 50% BF3−MeOH to produce a mixture of methyl 9- and 10-methoxyoctadecanoates. 14% BF3−MeOH does not react with cyclopropane and olefinic esters under the reaction conditions employed.
TL;DR: In this article, two new synthetic routes to a number of tetracyclic intermediates, for the total synthesis of some diterpenoids incorporating the bicyclo[3.2.1] octane moiety, are described.
TL;DR: In this paper, it was shown that insertion occurs preferentially into the less substituted cyclopropane bond, when R = n-C6H13, PhCH2, o-NO2C 6H4, or Ph.
Abstract: A series of mono-substituted cyclopropanes have been shown to displace ethylene from [(C2H4)PtCl2]2 with formation of substituted (propane- 1,3-diyl)PtCl2 derivatives, displacement being impeded or inhibited by electron withdrawing substituents. From the 1H n.m.r. spectra of the bis-pyridine derivatives (RC3H5)PtCl2(py)2 it is shown that insertion occurs preferentially into the less substituted cyclopropane bond when R = n-C6H13, PhCH2, o-NO2C6H4, or Ph, but for R =p-MeC6H4 the principal product arises from insertion into the more substituted bond in the cyclopropane. trans-1,2-Diphenyl- and trans-1-methyl-2-n-butyl-cyclopropane undergo insertion of PtCl2 into the less substituted cyclopropane bond, but cis-1-methyl-2-n-butylcyclopropane and bicyclo[4,1,0]heptane are preferentially isomerised to olefins. 1,2-Dicyclopropylethane yields a bis-PtCl2 derivative.
TL;DR: In this article, the insertion reaction between tetracarbonyldichlorodirhodium and phenylcyclopropane was examined, and the structures of rhodacyclopentanones deduced by sodium borohydride reduction.
Abstract: The insertion reaction between tetracarbonyldichlorodirhodium and phenylcyclopropane, benzylcyclopropane, and bicyclo[4,1,0]heptane has been examined, and the structures of the rhodacyclopentanones deduced by sodium borohydride reduction. Evidence is found for some cyclopropane → olefin isomerisation during the insertion reaction.
TL;DR: In this paper, it is suggested that the rate determining step is the cleavage of the cyclopropane ring to form the 1-3 diadsorbed species from a physically adsorbed or weakly chemisorbed precursor.
TL;DR: In this article, the double bond adjacent to the carbonyl group with 1-aryl-4-benzoylbuta-1,3-dienes and 1- Daryl-6-bensoylhexa- 1,3,5-trienes was confirmed by double 13 C NMR spectroscopy.
TL;DR: In this article, a cyclopropane synthesis in which a copper carbenoid complex was formed in the reaction of α-monochloro-carbonyl or nitrile with the cu2Ol-isonitrile complex was subjected to the reaction with an electron defecient olefin was reported.
TL;DR: In this paper, the thermal reactions of 1-aryl-1-cyclopropylethylenes and 1,1-dicyclopropyl-cyclohex-2-enone tricarbonyliron were investigated.
Abstract: The thermal reactions of 1-aryl-1-cyclopropylethylenes and 1,1-dicyclopropylethylene with pentacarbonyliron are investigated. Reactions of the former substrates yield 2-aryl-1,3-pentadiene-tricarbonyliron complexes via cyclopropane ring opening, hydrogen migration and coordination to iron. Reaction with the latter substrate gives 2-cyclopropyl-1,3-pentadienetricarbonyliron in similar fashion, and, in addition, 3-(1′-propenyl)-cyclohex-2-enone tricarbonyliron derived from the opening of the second ring coupled with carbon monoxide insertion. The cyclopropane ring serves as a two π-electron donor in these reactions, and the vinylcyclopropane system emerges as a novel source of four π-electrons which are available to coordination in direct analogy to reactions of formal diene systems with iron carbonyls.
TL;DR: In this article, the initial rates for cyclopropane isomerization and hydrogenolysis on amorphous (catalyst A) and crystalline (calyst C) chromium oxide are reported.
TL;DR: In this paper, the internal, copper-catalysed, addition of keto-carbenes to a double bond conjugated either to a ketone or carboxylic ester function has been found to be a feasible preparative reaction in selected cases.
Abstract: The internal, copper-catalysed, addition of keto-carbenes (generated from a diazoketone group) to a double bond conjugated either to a ketone or carboxylic ester function has been found to be a feasible preparative reaction in selected cases. This, together with the facile and regiospecific hydrogenolysis of the resulting 1,2-dicarbonyl cyclopropane intermediate, appear to constitute a convenient route to multifunctional bridged-ring systems.
TL;DR: In this article, photolysis of 3α,5-cyclo-5α-cholestan-6-one oxime affords two isomeric lactams with cyclopropane rings arising from photo-Beckmann rearrangement although the yields are poor.
Abstract: Photolysis of 3α,5-cyclo-5α-cholestan-6-one oxime affords two isomeric lactams with cyclopropane rings arising from photo-Beckmann rearrangement although the yields are poor. The result gives further support to our view on the C→N migration process in photo-Beckmann rearrangement. The major part of the products of the reaction consisted of the parent ketone and several products probably derived from it. The results are compared with those obtained in our photolysis of 5α-cholestan-6-one oxime and the isomeric 5β-cholestan-6-one oximes. The poor yields of the lactams is probably ascribable to the presence of the cyclopropane ring in this conjugated cyclopropyl ketone oxime.
TL;DR: A cell-free system from bramble tissues grown in vitro converts cycloeucalenol into obtusifoliol (II), and the implications of these results in terms of the biosynthetic pathway of phytosterols are discussed.