Anharmonic thermochemistry of cyclopentadiene derivatives

This paper focuses on the thermochemistry of some derivatives of cyclopenta‐1,3‐diene, namely, 5‐methylcyclopenta‐1,3‐diene, 5‐ethylcyclopenta‐1,3‐diene, 5‐formylcyclopenta‐1,3‐diene, 5‐methylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐ethylcyclopenta‐1,3‐diene‐1‐yl radical, 5‐carbonylcyclopenta‐1,3‐diene radical, 1‐formylcyclopenta‐2,4‐diene‐1‐yl radical, 5‐methylenecyclopenta‐1,3‐diene radical, 5‐ethylidenecyclopenta‐1,3‐diene radical, and 3,6‐dimethylenecyclohexa‐1,4‐diene. Several different chemistries of these compounds are of interest in combustion modeling. Here, we present gas‐phase thermochemical properties for the above cited species, which are, except for 3,6‐dimethylenecyclohexa‐1,4‐diene, previously unknown. These were obtained from corrected (using bond additivity corrections) high‐level ab initio quantum chemistry calculations validated with well‐known compounds including cyclopentane, cyclopentene, cyclopenta‐1,3‐diene, and cyclopentadienyl radical. Heat capacities and entropies have been corrected for anharmonic molecular motions, in particular for internal rotations. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 453–463, 2003     

Synthesis, characterization, and reactivity of ruthenium diene/diamine complexes including catalytic hydrogenation of ketones

Thermal reactions between [RuCl2(diene)]n (diene = 2,5-norbornadiene, nbd; 1,5-cyclooctadiene, cod) with an excess of N,N,N',N'-tetramethylethylene diamine (tmeda) afforded derivatives [RuCl2(diene)(tmeda)] (diene = nbd, 1; cod, 2) as a mixture of cis and trans isomers. When thermolysis was performed under H2 mixtures of hydride species [RuCl(H)(diene)(tmeda)] (diene = nbd, 3; cod, 4) and the bis-tmeda adduct trans-[RuCl2(tmeda)2] (5) were obtained in different ratios depending upon the reaction conditions and reaction times. Heating polymeric Ru(II) precursors in toluene in the presence of a 5-fold excess of the bulkier N,N,N',N'-tetraethylethylene diamine (teeda) resulted in a rare diamine dealkylation process with formation of trans-[RuCl2(nbd)(Et2NCH2CH2NHEt)] (6) and trans-[RuCl2(cod)(EtHNCH2CH2NHEt)] (7) in high yields. The presence of N-H functionalities in the coordinated diamine ligands of 6 and 7 was unambiguously established by single-crystal X-ray diffraction studies. The dealkylation process of the teeda ligand seems to proceed intramolecularly as shown by solution NMR studies performed with the soluble Ru(II) precursors trans-[RuCl2(amine)2(diene)] (diene = nbd, amine = morpholine, 9; diene = cod, amine = Et2NH, 10). The above complexes [RuCl2(diene)(diamine)] have been tested as precatalysts in the hydrogenation of ketones both for transfer as well as direct hydrogenation, the latter route being the most effective.     

A new diene, 2-methoxy-1,3-pentadiene-5-ol. Synthesis and intramolecular diels-alder reactions

Reactions of the diene 1-benzyloxy-2-methoxy-1,3-pentadiene-5-ol in intramolecular Diels-Alder reactions using maleic anhydride or fumaric acid ethyl ester is described. The new reactive diene is prepared starting from 3-methoxypyridine. The structure of the diene was elucidated by a NOE nmr experiment.     

A cobalt complex of a microbial arene oxidation product

ABSTRACT: We report the first synthesis of a cobalt Cp diene complex wherein the diene is derived by microbial dearomatising dihydroxylation of an aromatic ring. The complex has been characterised crystallographically and its structure is compared to that of an uncomplexed diene precursor.     

Stereochemistry of the formation of π-allylpalladium complexes from dialkylcyclohexa-1,3-dienes

1,4-Dimethyl-, 1-isopropyl-4-methyl- and 1-t-butyl-4-methylcyclohexa-1,3-diene reacted with a palladium salt to form, in each case, a single isomer of the corresponding π-allylpalladium chloride complexes, while 2-isopropyl-5-methylcyclohexa-1,3-diene gave two stereoisomeric complexes. An excess of diene (diene/Pd = 2.5–3.0) was required to produce a high yield of the complex. The hydrogen atom, which is incorporated onto the terminal carbon of the diene system, is shown (i) to come from the excess diene, which in turn is converted to an aromatic compound, and (ii) to attack the diene, stereo- and regio-selectively, from the same side as the palladium chloride portion.     

Intramolecular dealkylation of chelating diamines with Ru(II) complexes

N,N, N',N'-Tetraethylethylenediamine undergoes simple or double intramolecular dealkylation reactions in the presence of the complexes [RuCl2(diene)]n (diene = cod, nbd) or trans-[RuCl2(diene)(morfoline)2 at 80 degrees C to afford chelating amine ligands which contains one or two N-H functionalities.     

聚苯乙烯及其合金的热释放电流研究

聚苯乙烯及其合金的热释放电流研究盛京，李凤奎，胡静（天津大学材料科学与工程系，天津，３０００７２）关键词聚苯乙烯，聚苯乙烯松弛，热释电谱，聚苯乙烯合金，乙丙橡胶合金用热释放电流（ＴＳＣ）法研究聚苯乙烯（ＰＳ）的松弛过程只见Ｓｈｉｎｉｃｈｉ的报道［１］...     

Biaxial ordering of terminal diene groups in lipid membranes: an infrared linear dichroism study

The molecular order within the hydrophobic core of membranes of the diene lipid di-tetradecadienoylphosphatidylcholine was studied by means of infrared spectroscopy on multibilayer assemblies which orient macroscopically on the surface of an attenuated total reflection crystal. The relative humidity and temperature were used as variable parameters to demonstrate that there were profound differences in the melting transition of lipids possessing predominantly cis and trans diene groups. The cis isomer undergoes the phase transition at a vapor pressure which is increased by 0.15 GPa when compared with that of the trans isomer. The methylene wagging band progression gives no indication of differences between the acyl chain conformation of the cis and trans forms in the gel state. The frequencies of a number of absorption bands of the diene groups reveal that these moieties are predominantly in the s-trans conformation to accommodate a favorable packing within the bilayer. The linear dichroism of selected in-plane and out-of-plane vibrations of the diene groups gives indications of the biaxial ordering of these moieties. We present the basic equations for the quantitative analysis of IR dichroism data of lamellar structures in terms of transverse and longitudinal molecular order parameters. It turns out that the planes of the rigid diene groups orient preferentially in a perpendicular direction with respect to the bilayer surface and parallel to each other forming in this way a layer of well-aligned diene groups in the bilayer center. This finding is confirmed by the results of X-ray measurements. We suggest that the partial interdigitation of the diene groups of the sn-1 acyl chains promotes the formation of the inverse H_II phase and/or enables the formation of covalent bonds between both the monolayers upon polymerization of diene lipids.     

A theoretical study for the regioselective Diels–Alder reaction of 5,6‐fulleroid with strained anti‐Bredt olefins

Regioselectivity of Diels–Alder reaction of the anti‐Bredt olefin of fulleroid, the 5,6‐methylene‐bridged fullerene derivative, is theoretically clarified by DFT calculations. In transition state calculations, the addition of a noncyclic diene 2,3‐dimethyl‐1,3‐butadiene (DMBD) at the anti‐Bredt olefin has considerably lower activation energy than those at the other sixteen olefins, while the reaction of a rigid cyclic diene cyclohexadiene (CHD) has similar activation energy at both anti‐Bredt and another nontwisted olefin. The changes in strain and interaction of the reactants are estimated along its reaction coordinate by activation strain model. Noncyclic diene shows asynchronous C? C bond formation with a significant gain of interaction energy, while the rigid cyclic diene shows a large growth of strain energy canceling out the interaction energy between diene and fulleroid.     

Dienecobalt tricarbonyl cations

Oxidation of dienedicarbonylcobalt dimers has yielded the novel dienetricarbonylcobalt cations, or, in presence of phosphine, the corresponding mono- and di-substituted salts.     

Radical Cyclization of Fluorinated 1,3‐Dicarbonyl Compounds with Dienes Using Manganese(III) Acetate and Synthesis of Fluoroacylated 4,5‐Dihydrofurans

Radical cyclizations of fluorinated 1,3‐dicarbonyl compounds with dienes mediated by Mn(OAc)₃ afforded 4,5‐dihydrofurans containing difluoroacetyl, trifluoroacetyl, or heptafluorobutanoyl groups in good‐to‐excellent yields. Additionally, 2‐(difluoromethyl)‐4,5‐dihydrofurans and a 4,7‐dihydrooxepin derivative were obtained as unexpected products in the reaction of 4,4‐difluoro‐1‐phenylbutane‐1,3‐dione with 1,3‐diphenylbuta‐1,3‐diene. The radical cyclization of symmetrical dienes such as 2,3‐dimethylbuta‐1,3‐diene and 1,4‐diphenylbuta‐1,3‐diene with 1,3‐diketones furnished the corresponding products in low yields. However, treatment of 1‐phenylbuta‐1,3‐diene with 1,3‐dicarbonyl compounds afforded 4,5‐dihydrofurans containing fluoroacyl groups. The radical cyclizations with 3‐methyl‐1‐phenylbuta‐1,3‐diene and 1,3‐diphenylbuta‐1,3‐diene led to 4,5‐dihydrofurans in good yields, since Me and Ph groups at C(3) of these dienes increase the stability of the radical intermediate.     

Coordination chemistry of diphenylphosphinoferrocenylthioethers on cyclooctadiene and norbornadiene rhodium(i) platforms

Complexes [RhCl(diene)(P,SR)] with chiral ferrocenyl phosphine-thioethers ligands (diene = norbornadiene, NBD, 1(R), or 1,5-cyclooctadiene, COD, 3(R); P,SR = CpFe(1,2-η(5)-C(5)H(3)(PPh(2))(CH(2)SR); R = tBu, Ph, Bz, Et) and the corresponding [Rh(diene)(P,SR)][BF(4)] (diene = NBD, 2(R); COD, 4(R)) have been synthesized from [RhCl(diene)](2) and the appropriate P,SR ligand. The molecular structure of the cationic complexes 2(tBu), 4(Ph) and 4(Bz), determined by single-crystal X-ray diffraction, shows the expected slightly distorted square planar geometry. For the neutral chloride complexes, a combination of experimental IR and computational DFT investigations points to an equally four coordinate square planar geometry with the diene ligand, the chlorine and the phosphorus atoms in the coordination sphere and with a dangling thioether function. However, a second isomeric form featuring a 5-coordinated square planar geometry with the thioether function placed in the axial position is easily accessible in some cases.     

Polymer-supported electron-rich diene for hetero Diels-Alder reactions

A Brassard diene analogue was grafted on a modified Merrifield resin and used in a hetero Diels-Alder reaction with various aldehydes or ketones. The reaction gave access to 6-substituted 5,6-dihydropyrones (5a-u). This new immobilized electron-rich diene is more stable than the corresponding native diene, and is a versatile supported reagent.     

Nucleophilic attack of imidate anions on [Pt(diene)Cl2] complexes formation of compounds with PtN σ-bonds

A basic aqueous solution of maleimide or phthalimide reacts with [Pt(diene)Cl₂] complexes to give complexes of the type [Pt(diene)(imidate)₂] (diene = 1,5-cyclooctadiene, dicyclopentadiene and norbornadiene). The spectra and the reactions of these complexes give information about the nature of the PtN σ-bond.     

Short Access to Belt Compounds with Spatially Close CC Bonds and Their Transannular Reactions

Two domino Diels–Alder adducts were obtained from 3,7‐bis(cyclopenta‐2,4‐dien‐1‐ylidene)‐cis‐bicyclo[3.3.0]octane and dimethyl acetylenedicarboxylate or N‐methylmaleimide under microwave irradiation. From the first adduct, a C₂₀H₂₄ diene with C_2v symmetry was obtained by Zn/AcOH reduction, hydrolysis, oxidative decarboxylation, and selective hydrogenation. Photochemical [2+2] cycloaddition of this diene gave a thermally unstable cyclobutane derivative, which reverts to the diene. However, both the diene and the cyclobutane derivatives could be identified by X‐ray diffraction analysis upon irradiation of the diene crystal. New six‐membered rings are formed upon the transannular addition of bromine or iodine to the diene. The N‐type selectivity of the addition was examined by theoretical calculations, which revealed the distinct susceptibility of the doubly bonded carbon atoms to the bromine attack.     

Scalable synthesis of highly reactive 1,3-diamino dienes from vinamidinium salts and their use in Diels-Alder reactions

A practical and chromatography-free synthesis of vinamidinium salts and their use as diene precursors in Diels-Alder reactions is reported. Additionally, 1,3-dipyrrolidino-1,3-butadiene was shown to be significantly more reactive than Rawal's diene in a competition experiment.     

Cationic iron(III) porphyrin-catalyzed [4 + 2] cycloaddition of unactivated aldehydes with simple dienes

Cationic iron(III) porphyrin was found to be an efficient catalyst for the highly chemoselective hetero-Diels-Alder-type reaction of aldehydes with 1,3-dienes. The catalyzed process did not require the use of electron-deficient aldehydes such as glyoxylic acid derivatives or activated electron-rich 1,3-dienes such as Danishefsky's diene and Rawal's diene. The high functional group tolerance and robustness of the catalyst were demonstrated. Further, the potential utility of the catalyst was demonstrated by performing the cycloaddition in the presence of water and by carrying out cycloaddition of an unactivated ketone such as cyclohexanone with a diene.     

Molecular design of diene monomers containing an ester functional group for the synthesis of poly(diene sulfone)s by radical alternating copolymerization with sulfur dioxide

Functional poly(diene sulfone)s are prepared by the radical alternating copolymerization of 1,3‐diene monomers containing an ester substituent with sulfur dioxide. Methyl 3,5‐hexadienoate (MH) and methyl 5,7‐octadienoate (MO) with both an alkylene spacer and a terminal diene structure are suitable to produce a high‐molecular‐weight copolymer in a high yield, while the copolymerization of 5,7‐nonadienoic acid, ethyl 2,4‐pentadienoate, and ethyl 4‐methyl‐2,4‐pentadienoate including either an alkylene spacer or a terminal diene structure lead to unsuccessful results. The ¹³C NMR chemical shift values of MH and MO suggest a high electron density at their reacting α‐carbon for exhibiting a high copolymerization reactivity. Fluorene‐containing diene monomers, 9‐fluorenyl 3,5‐hexadienoate (FH) and 9‐fluorenyl 5,7‐octadienoate (FO), are also prepared and copolymerized with sulfur dioxide. The thermal and optical properties of the poly(diene sulfone)s containing the methyl and fluorenyl ester substituents in the side chain are investigated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1000–1009     

Synthesis of helical [2.2]paracyclophanes containing carbocyclic and heterocyclic five-membered rings

The preparation of a [2.2]indenoparacyclophane-based diene is described. Diels-Alder cycloadditions of this diene with N-methylmaleimide, N-phenylmaleimide and maleic anhydride occurred in good yields and anti-diastereoselectively only under high pressure conditions. Heterohelicenophanes were prepared by dehydrogenation of the Diels-Alder products with 10% Pd/C catalyst. A new helicenophanequinone was obtained by the reaction between the diene and 1,4-naphthoquinone.     

The use of d-glucose-based silyloxy dienes in anthracyclinone synthesis

We wish to report asymmetric Diels–Alder reactions using a d-glucose-based diene and quinol dienophile without requiring additional steps of preparing an oxirane dienophile typically used in the Stoodley group. A new d-glucose-based diene is also reported and its chemistry investigated.