Diene Molecules Research Articles

ChemInform Abstract: COMPLEXATIONS OF 1,4‐DIENES TO RHODIUM(I) PENTANE‐2,4‐DIONATES: THERMAL REARRANGEMENTS OF THE COMPLEXES.

AbstractAls Modelle für natürliche Produkte, die ein voneinander getrenntes Dien‐Fragment (‐ CH = CH ‐ CH3′‐ CH = CH ‐) enthalten, werden die 2,5‐Heptadiene (I) nach Literaturmethoden dargestellt und ihre Reaktionen mit den Rh(I)‐Komplexen (II) untersucht.

Characteristics of the mechanism of aromatization of low-molecular-weight aliphatic compounds on ultrahigh-silicate zeolites

1. With the help of14C-labeled compounds, we studied the transformations of methanol, lower olefins, and 1,3-pentadiene on ultrahigh silica zeolites (UHSZ) and obtained knowledge of the mechanism of growth of hydrocarbon skeletons in formation of olefins from methanol and aromatic hydrocarbons from 1,3-pentadiene. 2. We demonstrated experimentally the possibility of building up hydrocarbon chains by conversion of methanol on UHSZ by means of its reaction with olefins. At high and medium concentrations of lower olefins, the rate of this reaction is significantly higher than the rate of transformation of methanol into ethylene and the polymerization of ethylene, which, under these conditions, does not play a significant role in the formation of higher olefins. 3. We have shown that on formation of aromatic hydrocarbons from 1,3-pentadiene the formation of the hydrocarbon skeleton of arenes proceeds by way of fragmentation of pentadiene and subsequent buildups with the assistance of the fragments being formed from the dienes; cyclopolymerization of the initial 1,3-pentadiene does not play a significant role in the formation of aromatic hydrocarbons. 4. The basis of the suggestion that on reaction of methanol with 1,3-pentadiene on the surface of the UHSZ forms active particles (fragments), their reactions with the molecule of olefin or diene is characteristic of the UHSZ method of buildup of the hydrocarbon skeleton to the dimensions making possible the formation of an aromatic ring.

Complexations of 1,4-dienes to rhodium(I) pentane-2,4-dionates; thermal rearrangements of the complexes

As models for natural products containing a ‘skipped’ diene fragment (–CHCHCH2CHCH–), a series of hepta-2,5-dienes, hepta-2,5-dien-4-ols, and hepta-2,5-dien-4-ol acetates have been prepared. Some of these dienes react with either bis(ethylene)(pentane-2,4-dionato)rhodium(I) or bis(ethylene)(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)rhodium(I) to afford 1 : 1 complexes, e.g.[(E,E)-hepta-2,5-diene](1,1,1,5,5,5-hexafluoropentane-2,4-dionato)rhodium(I). Other dienes, e.g.(Z,Z)-hepta-2,5-diene, form 2 : 1 complexes in which for each molecule of diene, one double bond is co-ordinated to rhodium, whereas the other is not. The (Z,Z)-dienes do not form 1 : 1 complexes because there would be a severe steric interaction between the terminal substituents of each double bond in such complexes. For the complexes of the dienols and certain allylic alcohols (e.g. prop-2-en-1-ol), evidence was obtained for the presence of a stabilising intramolecular hydrogen bond between each OH and its nearest CO of the pentane-2,4-dionate. When heated in benzene with 5 mol % of bis(ethylene)(pentane-2,4-dionato)rhodium(I) each dienol rearranged to give an enone as, the main product [e.g.(E,E)-hepta-2,5-dien-4-ol →(E)-hept-2-en-4-one (85%)]. Their acetates rearranged to isomeric conjugated dienes [e.g.(Z,Z)-4-acetoxyhepta-2,5-diene →(3E,5Z)-2-acetoxyhepta-3,5-diene]. The hepta-2,5-dienes were recovered unchanged. The mechanisms of the rearrangements observed are explained in terms of intermediate (π-allyl)rhodium complexes.

Asymmetric hydrogenation catalyzed by aminophosphine-phosphiniterhodium complexes derived from natural aminoalcohols and x-ray crystal structure of (1,5-cyclooctadiene)-( S)- N-(diphenylphosphino)-2-diphenylphosphinoxymethylpyrrolidinerhodium(I) perchlorate

From the cheap and readily available amino alcohols ( S)-pyrrolidinemethanol (( S)-prolinol), and ( S)-α- N-ethyl-aminobutanol, we have obtained two new aminophosphine-phosphinite ligands: ( S)- N-(diphenylphospino)-2-diphenylphos- phinooxymethylpyrrolidine (( S)-Prolophos) and ( S)-1-diphenylphosphinoxy-2- N-ethyl- N-diphenylphosphinoaminobutane (( S)-Butaphos). The rhodium(I) complexes of these phosphines act as efficient homogeneous hydrogenation catalysts at ambient temperature and pressures for dehydro N-acetyl amino acids, dehydro N-benzoyl amino acids and itaconic acid. An X-ray diffraction study of the complex [Rh(COD)(( S)-Prolophos)][ClO 4]· THF has been shown that the crystals belong to the monoclinic space group P2 1 with a 10.680(2), b 10.448(2), c 18.207(3) Å and β 104.97(1)ldg. Refinements based on 2105 significant counter reflections led to a final R value of 0.060. The cation is in a distorted square planar geometry, the rhodium atom being bound to the two phosphorus atoms and to the two double bonds of the diene molecule.

Palladium alloys as hydrogen permeable catalysts in hydrogenation and dehydrogenation reactions

The nature and the concentration of the second component of a binary palladium alloy affects its catalytic activity in hydrogen addition and subtraction reactions with organic compounds. Hydrogen permeation across a palladium alloy catalyst enhances the rate and selectivity of hydrogenation compared with what is observed when the compound being hydrogenated is mixed directly with hydrogen. The principal product of diene hydrogenation when the hydrogen permeates through a membrane catalyst is not a saturated hydrocarbon but the corresponding olefin from which polymers can be synthesized. The rate of hydrogen atom addition to the diene molecules on the palladium alloy surface is higher than the rate of hydrogen atom recombination and desorption in the form of hydrogen molecules.

Electrophilic aromatic substitution. Part 29. The kinetics and products of the solvolyses in aqueous sulphuric acids of 2-cyano-3,4-dimethyl-4-nitrocyclohexa-2,5-dienyl acetate: the non-occurrence of an intramolecular 1,3-migration of the nitro-group in the solvolytic reactions of the diene. The kinetics and products of nitration of 2,3-and 3,4-dimethylbenzonitrile

The kinetics in 61.8–79.5% H2SO4 and the products formed in 61.8–84.3% H2SO4 for the solvolyses of the above-named diene have been determined. The reactions are interpreted as involving concurrent elimination of nitrous acid and AAL1 generation of the same ipso-intermediate as arises in the nitration of 2,3-dimethylbenzonitrile. This intermediate reacts by intermolecular rearrangement (as is proved by the isolation from the solvolyses of 2,3-dimethylbenzonitrile and the trapping of nitronium ion by reaction with 4-fluorophenol), by nucleophilic capture by water, and by 1,2-intramolecular rearrangement to 2,3-dimethyl-4-nitrobenzonitrile. The results permit the partitioning of the overall solvolytic rate coefficient and the demonstration that the derived coefficient for the reaction competing with the elimination depends on acidity as would be expected for an AAL1 reaction. The elimination of nitrous acid is also acid-catalysed and may not be a simple E1 reaction. The solvolytic reactions of the diene do not lead to a 1,3-intramolecular rearrangement of the nitro-group and the observed 1,3-rearrangement of the diene to give 2,3-dimethyl-5-nitrobenzonitrile under non-solvolytic conditions appears to be a thermal reaction of the diene molecule. By combining the solvolysis results with those for the nitration of 2,3-dimethylbenzonitrile in 70.4–82.5% H2SO4 it is shown that the major primary consequence of the nitration is ipso-attack and that it is possible to determine the positional reactivities in the nitrile.

BIS(η 4-2,3-dimethyl-1,3-butadiene)nickel

2,3-Dimethyl-1,3-butadiene reacts with (CDT)Ni to give a bis (η 4-diene)nickel complex in which the two diene molecules are arranged tetrahedrally around the central nickel atom.

Products of the reaction of Ru 3(CO) 12 with 1,3-cyclohexadiene. X-ray structure of (η-benzene)nonacarbonyl-1-cyclohexen-1,2-ylenetetraruthenium, Ru 4(CO) 9(C 6H 6)(C 6H 8)

The reaction between Ru 3(C0) 12 and 1,3-cyclohexadiene has been carried on under different conditions: contrary to previous findings Ru 3(CO) 12 does not catalyze the cleavage and the hydrogenation of 1,3-cyclohexediene. The products of the reaction have been characterized by i.r., n.m.r. and mass spectrometry. The crystal structure of the novel complex Ru 4(CO) 9(C 6H 6)(C 6H 8) has been determined by X-ray methods. Crystals are monoclinic, space group P2 1/2c with Z = 4 in a unit cell of'dimensions: a = 15.167(15), b = 10.114(9), c = 15.517(12) Å, β = 87.1(1)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R = 0.058 for 3828 observed reflections. A four metal atom cluster, in a “butterfly” arrangement, is coordinated by nine terminal CO groups, by a benzene molecule and a 1-cyelohexen-1,2-ylene unit obtained, respectively, by dehydrogenation and isomerization of two diene molecules.

Reaction of low-valent metal complexes with fluorocarbons. Part 30. Bis(cyclo-octa-1,5-diene)platinum with hexafluoroacetone, 1,1 -dicyano-2,2- bis(trifluoromethyl)ethylene and N-methylhexafluoroisopropylideneamine; crystal and molecular structures of [Pt2{(CF3)2CO}(1,5-C8H12)2] and [Pt·C(CF3)2·O·C(CF3)2O·(1,5-C8H12)

Reaction of [Pt(1,5-C8H12)2] with hexafluoroacetone affords, depending on reaction conditions, the complexes [Pt2{(CF3)2CO}(1,5-C8H12)2], [P[graphic omitted](1,5-C8H12)], and [P[graphic omitted]H- 1,5-C8H12)] and [P[graphic omitted](1.5-C8H12)]. The structural identities of the first two complexes have been established by the analysis of single-crystal X-ray data. The dinuclear complex is monoclinic, space group P21/c with four molecules in a unit cell of dimensions a= 9.917(3), b= 14.957(6). c= 13.358(3)A; β= 102.18(2)°. The structure has been solved by conventional heavy-atom methods from 2 083 diffracted intensities and refined to R 0.038 (R′ 0.044). The molecule contains an approximate mirror plane formed by the two platinum atoms [Pt–Pt 2.585(1)A] and the carbon and oxygen atoms of the hexafluoroacetone molecule, with the cyclo-octa-1,5- diene molecules symmetrically bonded to each platinum atom in the tub configuration.Crystals of the second complex are triclinic, space group P with two molecules in a unit cell of dimensions a= 8.212(3), b= 9.329(2), c= 12.610(3)A: α= 91.87(2). β= 102.10(2). γ= 111.25(3)°. The structure has been solved from 2 659 diffracted intensities to R 0.029 (R′ 0.035) by conventional methods. The platinum atom forms part of a five-membered condensed (head-to-tail) ring P[graphic omitted], and is co-ordinated by a cyclo-octa- 1,5-diene molecule in a tub configuration. In both compounds the platinum atoms show essentially square-planar co-ordination.In a third complex the hexafluoroacetone forms part of a five-membered ring, in which it links the platinum and an olefin carbon atom of cycle-octa-1,5-diene. A similar complex, [P[graphic omitted]H(1,5-C8H12)], is a minor product from the reaction of [Pt(1,5-C8H12)2] with 1,1 -dicyano-2,2-bis(trifluroromethyl)ethylene. N-Methylhexafluoroisopropylideneamine and [Pt(1,5-C8H12)2] afford [P[graphic omitted]Me(1,5-C8H12)].

Polymérisation anionique des diènes. IV. Contribution aux etudes des mécanismes de propagation stéréospécifique des isoprène et butadiène par les organo‐alcalins

AbstractBy taking into account different possible interactions between the living end, the counterion and the nature of the solvent used on the one hand, and the influence of the temperature on the kinetics and the microstructures of polydienes on the other hand, it has been possible to suggest some new explanations concerning the mechanisms of the anionic propagation of butadiene and isoprene. In hydrocarbon media, the stereospecificity of the 1,4 propagation initiated by lithium should be considered as the consequence of the coordination of the counterion by both of the two bonds of the diene molécule. The stereospecificity of the vinyl propagation by the same counterion in dioxane solvent should be the consequence of the competition between the (Li+, dioxane) and (Li+, diene) coordination complexations. In this case, the Li+ counterion should only be coordinated by only one of the two double bonds of the diene molecule. With isoprene, the π‐electron donation should originate mainly from the C3C4 double bond. The decrease of the stereospecificity is due to the increasing size of the alkali counterion and the separation or the dissociation of the growing ion‐pairs.

Palladium‐catalysed reactions of unsaturated compounds in non‐aqueous solvents: Reaction of conjugated and cumulated diolefins with π‐allylpalladium halides

AbstractInteraction of π‐allylpalladium halides with conjugated dienes leads to new π‐allylpalladium complexes via addition of the allyl fragment to the diene molecule. We succeeded in isolating the intermediate complexes in high yield and determining their structures. With conjugated dienes the addition takes place at the most substituted carbon atom in the π‐allyl fragment, contrary to what happens in the reaction with CO and allene. Substituents in the π‐allyl group and the other ligands bound to the metal prove to have a strong influence on the rate. For the bridging ligand the rate decreases in the order Cl > Br > CNS > I. For α‐or β‐substituted π‐allyl the order is Cl > COOR >> H > CH3. In combination with a kinetic investigation, the present study has provided a mechanism which accounts for the stereospecificity of the reaction and the accelerating influence of electron‐withdrawing groups.The results demonstrate the importance of π‐allyl transition‐metal intermediates in e.g. oligo‐ and polymerization of dienes. Repetition of the above‐described process leads with π‐allyl‐palladium halides to low‐molecular weight 1,2‐polymers of butadiene.

Chromium(II) chemistry. Part VI. Magnetic and spectroscopic studies of diethylenetriamine complexes

The chromium(II) complexes of diethylenetriamine (dien), Cr dien2X2, where X = Cl, Br, or I, have been shown to be high-spin and, from their diffuse reflectance spectra which are almost identical with those of tris(ethylenediamine)chromium(II) complexes, to have distorted octahedral structures. In solution in dimethylformamide, where the ethylenediamine complexes lose a ligand molecule, both dien molecules remain co-ordinated. The solution and solid-state spectra of the dien complexes are almost identical.From their antiferromagnetism and spectra the monoamine complexes Cr dien X2 are considered to have halide-bridged, binuclear structures with the dien molecules co-ordinated in a plane at right angles to the main distortion axis.

Condensation of oxazoles with dienophiles : Synthesis of vitamin B 6 analogues

Pyridoxine analogues have been synthesized via a Diels—Alder reaction of 5-ethoxyoxazoles with dimethyl maleate followed by reduction. The products on oxidation with manganese dioxide yielded pyridoxal analogues. Pyridoxamine derivatives were obtained by reduction of the pyridoxal oximes. Phosphorylation of the pyridoxamine analogues and the Schiff bases of pyridoxal compounds followed by hydrolysis afforded pyridoxamine phosphate and pyridoxal phosphate analogues, respectively. The mechanism of the Diels—Alder condensation of 5-ethoxyoxazoles is discussed on the basis of calculation of the π-electron charge distributions for diene and dienophile molecules according to the Hückel MO method. PMR, IR and UV spectra of the compounds synthesized and their TLC chromatography have been studied.

Low-Lying Pi—Sigma Transition in the Spectrum of Norbornadiene

A vibrational analysis of the first electronic band of norbornadiene (NBD), with origin at 45 120 cm−1, shows that the band is electronically allowed, the accompanying vibrations being totally symmetric. This is contrary to earlier theoretical work which assigned the band as N→V1, forbidden. A comparison with the spectra of cyclopentene and norbornene (NBE) suggests that the first band of norbornadiene is to be associated with the weak band of uncertain assignment found at approximately 45 000–50 000 cm−1 in all olefinic substances. Gross changes in the vibrational spacing and shape of the vibronic envelope are observed on freezing the NBD and NBE molecules in low-temperature matrices. The spectral changes appear to be due to modifications of the upper-state potential surfaces as a consequence of the rigidity of the matrix. There is some evidence in the NBD spectrum for weak vibronic coupling between the two halves of the diene molecule, and it is shown how the observed splitting pattern might be explained on such an assumption.

Structural orientation in the diene condensation of 2,4-pentadienoic acid with acrylic acid and with styrene

1. The condensations of 2,4-pentadienoic acid with acrylic acid and with styrene were carried out; structural isomers were isolated from the reaction products, and their proportions were determined. In both cases there was a great predominance of ortho adducts, mainly the trans isomers. 2. The polarities arising from the introduction of substituents into the diene and dienophile molecules do not constitute a determining factor in structural orientation in the diene synthesis.

Cation and Anion Influence in the Alfin Reagent for the Polymerization of Butadiene

Abstract A mixture of allylsodium, sodium isopropoxide and sodium chloride causes a very rapid polymerization of butadiene to a soluble polymer of unusually high molecular weight which has largely a 1,4-structure. The present work is a study of the influence of the sodium cation and of various halide salts, and of the isopropoxide ion as contrasted with the n-propoxide, upon the proportion of 1,4-polymerization. A proper combination of ions will favor greatly the end-to-end polymerization and any given reagent may cause either 1,4 or 1,2-polymerization to take place, depending on the composition of the reagent. An explanation based on adsorption and orientation of diene molecules on the surface of the insoluble aggregate of ions is suggested.