Mixture Of Dienes Research Articles

Stereochemistry of Eʹ and Eʹʹ decarboxylative-dehydration reactions and the bent bond / antiperiplanar hypothesis orbital model

The known concerted decarboxylative-dehydration reaction of unsaturated hydroxy-carboxylic acids 1–18 is analyzed through the Bent Bond/Antiperiplanar Hypothesis (BBAH), which considers double bonds as Pauling τ bonds. These reactions produce various mixtures of dienes or trienes having either the E or Z configuration. The relative formation of these mixtures of dienes or trienes can be rationalized through the BBAH model by the analysis of resonance structures leading to the antiperiplanar (APP) or the synperiplanar (SPP) electronic delocalization modes.

Selective removal of alkynes from diene mixtures using ether-functionalized Cu(i)-containing ionic liquids as extractants.

Cu(i)-Containing room temperature ionic liquids (Cu-EnA), prepared from CuCl and ether-functionalized ionic liquids (ILs) bearing a methanesulfonate anion (EnA, n = 1, 2 or 3), were thermally stable and highly effective for the removal of alkynes such as isopropenylacetylene (IPA) and 2-butyne (2-BT) contained in dienes like isoprene (2-methyl-1,3-butadiene). Cu-EnA were found to reversibly and selectively interact with IPA and 2-BT, thereby enabling the regeneration of Cu-EnA. Fast atom bombardment (FAB)-mass spectral and computational results imply that EnA consists of an ether-functionalized imidazolium cation and a methanesulfonate-coordinated Cu(i) anion such as [CuCl(CH3SO3)]- ([CuClA]-) or [Cu(CH3SO3)2]- ([CuA2]-). Computational studies demonstrate that the preferential extraction of IPA and 2-BT to isoprene by Cu-EnA originated from the difference in the strength of the hydrogen bonding and π-complexation.

Pervaporation Separation of Cyclopentadiene/Methylcyclopentadiene Mixtures from Cracking C5 Fractions Using Polyimide Membranes

Polyimide membrane pervaporation was introduced to separate the costly diene mixtures of cyclopentadiene/methylcyclopentadiene (CPD/MCPD) from cracking C5 fractions. Four kinds of membrane solutions were prepared and two kinds of polyimide homogenous membranes were fabricated by thermal imidizations using the dianhydrides (BPADAand PMDA) and the diamines (ODA and DDS). The effect of the casting solutions viscosity on the membrane formation was revealed, and the formation of functional groups and the synthesis mechanisms of the thermal imidizations were indicated by FT-IR. The adsorption behaviors and the pervaporation performances were studies for BPADA-ODA and PMDA-ODA membranes. The results show that the permeation fluxes are 164g∙m-2∙h-1 and 4.2g∙m-2∙h-1 for BPADA-ODA and PMDA-ODA membranes respectively, while the separation factor are 1.93 and 8.9 for these two membranes respectively. 88.5 wt% concentration of MCPD was achieved in the circulated feed side ultimately.

Reaction of levoglucosenone with (±)-α-terpineol and its acetate

In continuation of our studies [1, 2], we focused on the potential of levoglucosenone in the synthesis of menthane derivatives as a separate problem and examined the possibility for direct introduction of a menthane fragment into levoglucosenone molecule via reaction with (±)-α-terpineol. A short synthetic route to (±)-α-terpineol is the twostep procedure utilizing large-scale initial compounds, isoprene and methyl acrylate [3]. The transformation of (±)-α-terpineol into a chiral subunit requires its preliminary optical resolution and introduction of functional groups that could ensure subsequent transformations. It is known that dehydration of α-terpineol leads to the formation of a number of isomeric dienes, including α-terpinene whose yield in some cases attains 25% [4]. The use of such a mixture of menthane derivatives as diene component and of levoglucosenone as dienophile is attractive from the viewpoint of simultaneous solution of both problems. For this purpose, a toluene solution of levoglucosenone and diene mixture obtained from (±)-α-terpineol according to the procedure described in [4] was heated at 160°C in a sealed glass ampule (metohd a). In fact, after 9 h, we succeeded in isolating from the reaction mixture Diels–Alder adduct V in 3% yield [calculated on the initial (±)-α-terpineol]. Increase of the reaction time reduced the yield of V, and we failed to detect it in the reaction mixture after 30 h, presumably because of its decomposition. We also tried to use as starting compounds (±)-α-terpineol (I) and (±)-α-terpinyl acetate (II), expecting generation of α-terpinene (III) in situ under the given Diels–Alder reaction conditions. In the first case, no cycloaddition products were detected in the reaction mixture, and in the second case adduct V was formed in 4% yield in 28 h (method b). The structure of V was determined on the basis of the H and C NMR data. The coupling constant between 5a-H and 9a-H equal to 8.6 Hz indicates cis junction of the bicyclo[2.2.2]octane and pyran fragments. The signal assignment was confirmed by the HMBC technique. The 9a-H proton (δ 1.87 ppm) showed couplings with C (δC 68.29 ppm), C (49.29), C (200.96), C (138.26), and C (35.59), and cross-peaks of 5a-H (δ 2.90 ppm) with C, C (δC 44.98 ppm), C (135.53), and C (20.80) were

Addition of Dissimilar Carbenes across an Unsymmetrically Substituted Alkyne: Regio- and Stereoselective Synthesis of Trisubstituted 1,3-Dienes

The formal addition of dissimilar carbenes across an unsymmetrically substituted alkyne has been achieved for the first time by a two-step sequence in which a cobalt−alkyne complex undergoes reaction with a carbene addend (CHR1) to give a metallacyclobutene complex, followed by reaction with a second carbene addend (CHR2) to give a mixture of diene complexes. In situ treatment of the diene mixture with fluoride leads to desilylation and conversion to a single cobalt−diene complex with a high degree of regio- and stereoselectivity.

Parallel Kinetic Resolution Approach to the Cyathane and Cyanthiwigin Diterpenes Using a Cyclopropanation/Cope Rearrangement

Parallel effort: Stereodivergent parallel kinetic resolution of a racemic mixture of dienes using Davies' [Rh(2){(S)-dosp}(4)] or [Rh(2){(R)-dosp}(4)] catalysts promotes a tandem vinyl diazoacetate cyclopropanation/Cope rearrangement sequence to afford two diastereomeric, enantioenriched cycloheptadienes, which correspond to the natural antipodes of the title diterpenoids (see scheme).

Total synthesis of Angucyclines. Part 18: A short and efficient synthesis of (+)-ochromycinone

A short and highly enantiospecific (seven steps, 99% ee) synthesis of (+)-ochromycinone 2 in 19% overall yield is reported. Key steps are the regioselective Diels–Alder reaction of the juglone derivative 4 with the mixture of dienes 5 and 9 derived from 3-methylcyclohexanone (99% ee) and the photooxidation of 1-deoxyochromycinone 3 to the natural ketone 2 . A pronounced concentration dependence of the specific rotation was observed for (+)-ochromycinone 2 in CHCl 3.

A Model study for Diels–Alder reaction of biscyclopentadienyl monomer with bismaleimides. Benzylcyclopentadiene: synthesis, characterization and Diels–Alder reaction with N-(4-benzoyl)-phenylmaleimide

Reaction between benzylbromide and sodium cyclopentadienide leads to a mixture of dienes. These can be identified by several techniques such as size exclusion chromatography, mass spectroscopy (MS) and high performance liquid chromatography/MS coupling. Their structure is confirmed by analysis of adducts obtained after reaction of N-(4-benzoyl)-phenylmaleimide with these dienes.

Borabenzene Derivatives. 27. From (−)-α-Pinene to the First Chiral Boratabenzene Salt1

Enantiomerically enriched (−)-α-pinene (3) is used to synthesize the β-pinene-derived alcohol 5 with a 3-exo-CMe2OH group. Dehydration with (CF3SO2)2O/pyridine produces a diene mixture 6 which, by means of double kaliation and subsequent ring closure with BCl2(NMe2), is transformed into the tetrahydroborinine 7. Metalation of 7 affords the enantiomerically pure lithium boratabenzene 8 in 80% yield (based on 6).

Statistical modeling and Monte Carlo studies of silicone-carbon resins

The Pt-catalyzed hydrosilation reaction between methyl-substituted cyclosiloxane and a nonconjugated diene system produces silicone-carbon polymers with good mechanical and dielectric properties. In this work a statistical model is devised that provides a theoretical description of the polymerization reaction up to the B stage. An ensemble of cyclosiloxane molecules is built up in a computer and allowed to “react” with the diene (or mixture of dienes) in a Monte Carlo process. Included in the model are options for batch or semibatch operations. Through computer simulation, the concentrations of all molecular species at different conversions (as measured by the residual Si(SINGLE BOND)H group) can be predicted as well as the molecular weight distribution. Good agreement is obtained with observed analytical data. The model is flexible and is used to study the effects of the changes in reaction process conditions on polymer structures and molecular weights. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 607–618, 1997

3-Hydroxy-dihydrosantoninとTsOHの反応.Dihydrocotunolideの形式的合成

In connection with our another project a relatively large quantity of 5 was required. We, therefore, investigated the reaction of 3 with TsOH; this gave a diene mixture 7a, 7b, 6 and 5 in a ratio of 8:2:4:1. Almost the same 8:2:1 "equilibrium mixture" of the dienes 7a, 7b and 5 was also obtained when the purified samples of 5 and 7a were independently treated with TsOH under the same conditions. The above results suggest that the dienes might be produced in the following way; beta-elimination of H2O from 3 gives a homoannular diene 5. The protonation to the more electron-rich tetrasubstituted C4-C5 double bond of 5 from the less hindered alpha-side followed by the isomerization of the double bond gives 7a. 7b is formed via 7a and/or 5 by the double bond isomerizations. On the other hand, 6 is formed by concerted elimination of H2O between C3-OH and C6-H. As a result of these studies, the synthetic precursor of dihydrocostunolide 7b which was already prepared by Corey in 6 steps (ca. 7%) from santonin was synthesized in 3 steps (ca. 6%) from the latter.

Inhibitors of sterol synthesis. An improved chemical synthesis of 26-oxygenated Δ8(14)-15-ketosterols having the 25R configuration

(25R)-3β,26-Dihydroxy-5α-cholest-8(14)-en-15-one (I) was synthesized in four steps from (25R)-3β,26-diacetoxycholesta-5,7-diene (III) in 30% overall yield. Isomerization of III with HCI in chloroform-dichloromethane at −60°C gave (25R)-3β,26-diacetoxy-5α-cholesta-7,14-diene together with the 5 α- Δ 8,14 and 5 β- Δ 8,14 isomers in a 5:1:1 ratio. Epoxidation of the crude diene mixture with m-chloroperbenzoic acid, followed by hydrolysis in acetone containing concentrated HC10 4 (0.1%) gave (25R)-3β,26-diacetoxy-5α-cholest-8(14)-en-15-one (VIII), accompanied by numerous minor byproducts, including the 5 α,14 β- Δ 7, 5 α, 14 β- Δ 8 and 5 β,14 β- Δ 8 isomers of VIII. All four 15-ketosterol esters were isolated by chromatography and fully characterized by mass spectrometry and 1H and 13C nuclear magnetic resonance. Treatment of VIII with potassium carbonate in degassed methanol gave I.

Cyclobutene photochemistry. 4. The photochemistry of cis- and trans-bicyclo[5.2.0]non-8-ene

Direct photolysis of cis- and trans-bicyclo[5.2.0]non-e the diene mixtures are in both cases weighted in favor of the less thermodynamically stable cis,trans isomer. The product distributions vary only slightly with excitation wavelength over the 185-214-nm range. Quantum yields for direct photoisomerization of cis,cis- and ck,trans-l,3-cyclononadiene have also been determined. Two mechanisms are considered to explain the nonstereospecificity associated with the ring-opening process: a nonconcerted pathway involving initial cyclobutene bond homolysis and subsequent relaxation of common biradical intermediates, and a pericyclic pathway involving adiabatic, disrotatory ring opening to yield dienes in the first excited singlet state. While the results do not allow a definitive distinction between the two mechanisms, the nonconcerted pathway is suggested to be the more reasonable on the basis of the photobehavior of other cyclobutene derivatives that have been studied. The quantum yield of cycloreversion product is ca. 4 times higher from the cis isomer compared to that from the trans isomer, due to the stereochemical requirements of the process.

Precise characterization of cuticular compounds in youngDrosophila by mass spectrometry

Cuticular hydrocarbons of youngDrosophila flies are singular with very long chains and complex diene mixtures. A precise characterization of these substances was carried out by epoxidation and analysis of the products by GC-MS with negative chemical ionization. InD. melanogaster, double bonds of dienes are more probable at carbon positions 11 or 13 and 21 or 23. InD. simulans, double bonds are shifted more towards the interior of the chain. Such a difference is also found among monoenes of both species. The analyses of monoenes and dienes confirm the similarity of cuticular compounds of young flies of both sexes in both species. A main cuticular compound ofD. erecta females, 9, 23-tritriacontadiene, is also presented.

ChemInform Abstract: 1,2‐Carbonyl Transposition with Concomittant Dehydrogenation in 1,5‐Dimethylbicyclo(3.3.0)octane‐3,7‐dione.

AbstractImprovements are reported for the conversion of the diketone (I) into the mixture of dienes (II) and (III).

Relationships between structure and chromatographic retention for n-alkadienes

The chromatographic behavior of n-alkadienes was studied by high-performance liquid chromatography on a silver nitrate-coated silica column and by gas chromatography on a non-polar capillary column. The retentions of 89 synthetic Z,Z and E,Z diene standards, of 18–38 carbons, were determined. Multiple regression models for retention were developed for both columns, based on double-bond configurations, sizes of the terminal alkyl groups, and the numbers of carbons between double bonds. The use of these chromatographic columns in the analysis of complex mixtures of dienes from natural sources is discussed.

Ethylene polymerization with high activity catalysts prepared from titanium tetrachloride and magnesium diene adducts

Magnesium (isoprene) 2 adducts were prepared in THF and transferred to toluene solutions. The products from the reaction of these solutions with TiCl 4 gave highly active catalysts for ethylene polymerization when used with aluminium trialkyl co-catalysts. Results of polymerizations under various conditions are given. Comparison experiments were carried out with catalysts prepared from magnesium myrcene and magnesium diphenyl butadiene adducts. Reaction products of TiCl 4 and magnesium diene mixtures were separated into soluble and insoluble fractions and analysed.

Reactions of tetrafluoroethylene oligomers. Part 1. Some pyrolytic reactions of the pentamer and hexaher and of the fluorine adducts of the tetramer and pentamer

Pyrolyses of these highly branched fluorocarbons over glass beads caused the preferential thermolyses of CC bonds where there is maximum carbon substitution. Fluorinations of perfluoro-3,4-dimethylhex-3-ene (tetramer) (I) and perfluoro-4-ethyl-3,4-dimethylhex- 2-ehe (pentamer) (II) over cobalt (III) fluoride at 230° and 145° respectively afforded the corresponding saturated fluorocarbons (III) and (IV), though II gave principally the saturated tetramer (III) at 250°. Pyrolysis of III alone at 500—520° gave perfluoro-2-methylbutane (V), whilst pyrolysis of III in the presence of bromine or toluene afforded 2-bromononafluorobutane (VI) and 2H-nonafluorobutane (VII) respectively. Pyrolysis of perfluoro-3-ethyl-3, 4-dimethylhexane (IV) alone gave a mixture of perfluoro-2-methylbutane (V), perfluoro-2-methylbut-1-ene (VIII), perfluoro-3-methylpentane (IX), perfluoro-3,3-dimethylpentane (X), and perfluoro-3,4- dimethylhexane (III). Pyrolysis of IV in the presence of bromine gave (VI) and 3-bromo-3-trifluoromethyl-decafluoropentane (XI): with toluene, pyrolysis gare VlI and 3H-3-trifluoromethyldecafluoropentane (XII). Pyrolysis of II at 500° over glass gave perfluoro-1,2,3-trimethylcyclobutene (XIII) and perfluoro-2,3-dimethylpenta-1,3(E)- and (Z)-diene (XIV) and (XV) respectively. The diene mixture (XIV and XV) was fluorinated with CoF 3 to give perfluoro-2,3-dimethylpentane (XVI) and was cyclised thermally to give the cyclobutene (XIII). Pyrolysis of perfluoro-2- (1′-ethyl-1′-methylpropyl)-3-methylpent-1-ene (XVII) (TFE hexamer major isomer) at 500° gave perfluoro-1-methyl-2-(1′-methylpropyl)cyclobut-1-ene (XVIII) and perfluoro-2-methyl-2-(1′-methylpropyl)buta-1,3-diene (XIX). Fluorination of XVIII over CoF 3 gave perfluoro-1-methyl-2- (1′-methylpropyl)cyclobutane (XX), which on co-pyrolysis with bromine gave VI. XIX on heating gave XVIII. Reaction of XVIII with ammonia in ether gave a mixture of E and Z 1′-trifluoromethyl-2-(1′-trifluoromethyl- pentafluoropropyliden-1′-yl)tetrafluorocyclobutylamine (XXI) which on diazotisation and hydrolysis afforded 2-(2′trifluoromethyl- tetrafluorocyclobut-1-en-1′-yl)-octafluorobutan-2-ol (XXII).

Polyfluoroalkyl derivatives of nitrogen. Part 48. The addition of N-halogenoamines (CF3)2NX to cyclohexa-1,3- and -1,4-dienes; a new synthesis of NN- bistrifluoromethylaniline

Treatment of cyclohexa-1,3-diene with the N-halogenoamines (CF3)2NX (X = Cl or Br) at –78 °C gives a mixture of the 1 : 1 adducts, trans-(CF3)2N–[graphic omitted]H and cis- and trans-(CF3)2N–[graphic omitted]H2; in contrast (CF3)2NI affords the former adduct exclusively. All three amines react with cyclohexa-1,4-diene under analogous conditions to yield the 1 : 1 adduct trans-(CF3)2N–[graphic omitted]HX only. Dehydrohalogenation of the 1,3-diene adducts (X = Cl or Br) with various bases (KOH powder, PriONa, ButOK) affords a mixture of 1- and 2-(NN-bistrifluoromethylamino)cyclohexa-1,3-diene. The latter diene forms a Diels–Alder adduct with trifluoronitrosomethane and the diene mixture dehydrogenates readily over a Pd–C catalyst at 180–190 °C to give NN-bistrifluoromethylaniline exclusively in high yield.

ChemInform Abstract: ELECTRONIC EXCITED STATES OF SMALL RING COMPOUNDS. SUBSTITUENT EFFECTS ON THE PHOTOCHEMICAL RING CLEAVAGE OF 3,3‐DIMETHYL‐1,2‐DIARYLCYCLOPROPENES

AbstractBei der Belichtung der Diarylcyclopropene (Ia) und (Ib) entstehen die Verbindungen (IIIa) bzw. (IIIb) und zusätzlich aus (Ia) das Dien (IIa).