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Showing papers on "Norbornadiene published in 2002"


Journal ArticleDOI
TL;DR: In this paper, the applicability of the valence isomerization of norbornadiene and its derivatives for the storage of solar energy is discussed, and a bibliography includes 112 references.
Abstract: Data on the valence isomerisation of norbornadiene and its derivatives into the corresponding quadricyclanes published between 1990 and 2001 are considered and described systematically. The applicability of this reaction for the storage of solar energy is discussed. The bibliography includes 112 references.

121 citations


Journal ArticleDOI
TL;DR: A significant improvement of the catalytic system for Rh-catalyzed intramolecular Alder±ene reactions of enynes is reported, screening a number of chiral phosphane ligands to achieve high enantioselectivities.
Abstract: Alder±ene reactions are a powerful way to construct carbon±carbon bonds. The intramolecular version of these reactions can provide efficient routes to produce a variety of heterocyclic and carbocyclic compounds.[1] Since the thermal Alder±ene reaction requires high temperature, it has found limited applications in organic syntheses. In contrast, transition-metal-catalyzed Alder±ene reactions can be performed under mild conditions and therefore are widely applied to organic syntheses.[2] However, the enantioselective processes of metal-catalyzed Alder±ene reactions are relatively unexplored and the development of highly efficient catalysts still remains a great challenge.[3] Recently, we have developed Rhcatalyzed intramolecular Alder±ene reactions of enynes using a [{Rh(diphos)Cl}2] precursor.[4] Enantioselectivities between 65±98% ee were obtained by using 1,2-bis(phospholano)benzene (Duphos), (2R,2’R)-bis(diphenylphosphanyl)-(1R,1’R)dicyclopentane (BICP), or the related (2R,2’R)-bis(diphenylphosphinite)-(1R,1’R)-dicyclopentane (BICPO) as chiral ligands.[4a] Herein, we report a significant improvement of the catalytic system for these reactions. The new catalysts are prepared in situ by simply mixing a commercially available metal precursor and a ligand. Over 99% ee has been achieved for a number of substrates. To achieve high enantioselectivities for Rh-catalyzed Alder±ene reactions, we have screened a number of chiral phosphane ligands. The enyne 1a was chosen as a standard substrate to optimize the reaction conditions and the results are given in Table 1. In the absence of phosphane ligand, [{Rh(cod)Cl}2] was an ineffective catalytic precursor at either room temperature or 65 8C (Table 1, entries 1 and 2). However, [{Rh(nbd)Cl}2] (nbd1⁄4 norbornadiene) can be used as a catalyst precursor at 65 8C (Table 1, entry 6). Using the CnTunaphos ligands developed by our group,[5] high efficiency was observed. When rac-C4-Tunaphos was used as the ligand in the presence of [{Rh(cod)Cl}2] and AgSbF6, high conversion (100%) and a high yield (98%) were obtained at room temperature within 20 min (Table 1, entry 9). Control experiments indicated that there were big differences between this new catalytic system and the earlier protocol developed by us using [{Rh(diphosphane)Cl}2] as catalytic precursor. We previously reported that [{Rh(BINAP)Cl}2] (BINAP1⁄4 2,2’COMMUNICATIONS

82 citations


Journal ArticleDOI
TL;DR: In this article, Ag[closo-CB11H12] to [(PPh3)2RhClCl]2 affords the new exopolyhedrally coordinated complex (PPh 3)2RCl(closoCB 11H12)] (1), which has been characterized by multinuclear NMR spectroscopy and X-ray crystallography.

71 citations


Journal ArticleDOI
TL;DR: The rigid backbone tetradentate (phosphino)amines 1,4-{(Ph2P)2N}2C6H4, 1, 4-{ (Ph 2P) 2NCH2CH2SCH 2SCH2}4C6-H2 were readily prepared in one-step by full phosphinylation of the appropriate primary amine with Ph2PCl in Et2O with NEt3 as auxiliary base as discussed by the authors.

65 citations


Journal ArticleDOI
TL;DR: A series of calixarenes bearing diphenylphosphino groups tethered at the upper rim have been prepared by treatment of 5,11,17,23-tetrabromo-25,26,27,28-tetrapropoxycalix[4]arene with ButLi (or BunLi) followed by reaction with PPh2Cl as mentioned in this paper.
Abstract: A series of calix[4]arenes bearing diphenylphosphino groups tethered at the upper rim have been prepared by treatment of 5,11,17,23-tetrabromo-25,26,27,28-tetrapropoxycalix[4]arene with ButLi (or BunLi) followed by reaction with PPh2Cl. The tetraphosphinated derivative 3 was found suitable for the formation of tetranuclear species, notably [3·(AuCl)4], [3·{RuCl2(p-cymene)}4], and [3·{PdCl(o-C6H4CH2NMe2)}4], all possessing an apparent C4v-symmetry in solution. Reaction of [RuCl2(p-cymene)]2 with the diphosphines 5,17-di-X-11,23-bis(diphenylphosphino)-25,26,27,28-tetrapropoxycalix[4]arene (X = H, 1; X = Br, 4) afforded the C2v-symmetrical dinuclear complexes [1·{RuCl2(p-cymene)}2] and [4·{RuCl2(p-cymene)}2], respectively. Reaction of the non-brominated diphosphine 1 with [PdCl(o-C6H4CH2NMe2)]2 gave the complex [1·{PdCl(o-C6H4CH2NMe2)}2]. Reaction at high dilution of [PtCl2(1,5-cyclooctadiene)] with 4 or 1 resulted in quantitative formation of the corresponding cis-chelate complexes [4·PtCl2] (12) and [1·PtCl2] (13), respectively. The trans version of 13 could also be obtained, provided that [PtCl2(PhCN)2] was used as starting complex. In the solid state, the PtCl2 unit of 12 is directed towards one bromine atom, resulting in a highly unsymmetrical calixarene structure where the metal plane is nearly parallel to the calix reference plane. The NMR spectra of 12 and 13 show an apparent C2v-symmetrical structure, suggesting a fast fan-like motion in solution of the metal plane about the P⋯P axis. Similar dynamics are likely to occur in the related cationic complexes [1·Rh(norbornadiene)]BF4 (15) and [1·Pd(Me-allyl)]BF4 (16). As shown by variable temperature studies carried out on 12 and 16, these dynamics couple with a concomitant, restricted rotation of the two PPh2 units about their coordination axis. The latter motion is probably a result of steric interactions within the phosphorus environment, two PPh rings being in competition for occupation of the cavity entrance. Reaction of the expanded cavity 5,11,17-tribromo-23-diphenylphosphino-25,26,27,28-tetrapropoxycalix[4]arene 5 with [RuCl2(p-cymene)]2 afforded the monophosphine complex [5·RuCl2(p-cymene)]. In solution as well in the solid state, the p-cymene ligand fills the calixarene basket.

57 citations


Journal ArticleDOI
TL;DR: In this article, the thermal cis-trans isomerization of polyphenylacetylene (PPA) synthesized with Noyori's catalyst was investigated under both ambient and inert atmospheres in solution and in bulk.
Abstract: The thermal cis-trans isomerization of cis-transoidal polyphenylacetylene (PPA) synthesized with Noyori's catalyst [Rh(C≡CPh)(norbornadiene)(PPh 3 ) 2 ] has been investigated under both ambient and inert atmospheres in solution and in bulk. In all cases, an intramolecular cyclization results in cis-trans isomerization, and subsequent chain cleavage produces 1,3,5-triphenylbenzene. This reaction is accelerated by the presence of air, particularly when the reaction takes place in solution. Decreases in the cis content and molecular weight show that the intramolecular cyclization process takes place at 23 °C in solution. The mechanism of this reaction is identical to that reported previously for cis-cisoidal and cis-transoidal PPA synthesized with Ziegler-Natta catalysts.

57 citations


Journal ArticleDOI
TL;DR: In this paper, the ionic liquids n -butylpyridinium tetrafluoroborate [bupy]BF 4 and 1-n-butyl-3methylimidazolium tetraploborate (BF 4) were used as solvents for the Rh(I) catalyzed phenylacetylene polymerization in the presence of triethylamine as co-catalyst.
Abstract: The ionic liquids n -butylpyridinium tetrafluoroborate [bupy]BF 4 and 1- n -butyl-3-methylimidazolium tetrafluoroborate [bmim]BF 4 have been used as solvents for the Rh(I) catalyzed phenylacetylene polymerization in the presence of triethylamine as co-catalyst, obtaining high yields of poly(phenylacetylene). The complexes used are (diene)Rh(acac) and [(diene)RhCl] 2 [diene: 1,5-cyclooctadiene or norbornadiene]. The (nbd)Rh(acac) complex in both ionic liquids can be recycled without significant loss in activity. Molecular weights in the range between 55,000 and 200,000 Da have been obtained by GPC.

52 citations


Journal ArticleDOI
TL;DR: ROMPgel-supported triphenylphosphine was synthesized in three steps (67%) from norbornadiene, 4-bromoiodobenzene, and chlorodiphenylPhosphine and gave the corresponding products in high yield and purity.

50 citations


Journal ArticleDOI
TL;DR: Both the allyl complex and the molybdate complex are the only metal-containing species observed by NMR in typical catalytic reactions and thus appear to be catalyst resting states.
Abstract: Spectroscopic and crystallographic studies were undertaken to gain insight into the mechanism of the highly regio- and enantioselective allylic aklylation reaction catalyzed by molybdenum. The chiral ligand (L*) consisting of the mixed benzamide/picolinamide of (S,S,)-trans-1,2-diaminocyclohexane reacts with a typical Mo precatalyst, (norbornadiene)Mo(CO)4, to give a neutral complex L*Mo(CO)4 in which the ligand binds to the metal in a bidentate fashion through the pyridine and adjacent amide group. Reaction of this complex with the methyl carbonate of cinnamyl alcohol gives the corresponding π-allyl complex L*(CO)2Mo(η3-CH2CH−CHPh). NMR and X-ray crystallographic characterization of this complex reveal the ligand binds in a facially capping tridentate fashion via the pyridine nitrogen, the nitrogen of the adjacent amide group, which has now been deprotonated, and the carbonyl oxygen of the remote amide. Surprisingly, the face of the allyl group open to attack with nucleophiles is that which would lead to...

44 citations


Journal ArticleDOI
TL;DR: Optimization studies on a palladium-catalyzed tandem norbornadiene insertion-Suzuki coupling reaction, which provides a one-pot procedure for the formation of diarylnorbornene derivatives, are presented.
Abstract: This paper presents optimization studies on a palladium-catalyzed tandem norbornadiene insertion−Suzuki coupling reaction, which provides a one-pot procedure for the formation of diarylnorbornene derivatives. This procedure allows for the synthesis of these compounds from readily available aryl halides, arylboronic acids, and substituted norbornadienes.

38 citations


Journal ArticleDOI
TL;DR: The reduction of Ni(S2C2(CF3)2)2(C7H8) (3) proceeds by an overall two-electron irreversible process through an ECE mechanism.
Abstract: The reduction of Ni(S2C2(CF3)2)2(C7H8) (3) proceeds by an overall two-electron irreversible process through an ECE mechanism. The reduction potential of 3 is about 700 mV negative of that in an earlier report, which is shown to result from contamination of the sample by the monoanion of the olefin-free complex [Ni(S2C2(CF3)2)2]-.

Journal ArticleDOI
TL;DR: In this paper, a columnar assembly of polyacetylene esters was characterized using 1 H and 13 C NMR spectroscopy, X-ray diffraction, and atomic force microscope methods.
Abstract: Alkyl propiolates: HC≡CCOOn-C m H 2m+1 (m = 2∼4), acetylene esters were polymerized with a [Rh(norbornadiene)Cl] 2 catalyst in methanol as the polymerization solvent to produce poly(n-alkyl propiolate)s, PAPAs, called polyacetylene esters, in relatively high yields. The resulting PAPAs were characterized in detail using 1 H and 13 C NMR spectroscopy, X-ray diffraction, and atomic force microscope methods. The data showed that the resulting polymers selectively have cis-transoid form. The cis-transoid isomer is not amorphous but holds a pseudohexagonal structure called a columnar assembly the diameter of which agrees with those estimated by the semiempirical calculation method (AM1). The crystalline ratios of the columnar assemblies were also estimated to be ca. 60∼70%. In the case of poly(ethyl propiolate), PEPA, the crystalline size was found to approximately agree with that estimated from the AFM images of the cast film of PEPA.

Journal ArticleDOI
TL;DR: In this article, a ring-opening metathesis polymerization (ROMP) reaction between cyclic olefins and the metal complex was monitored by means of 1 H -and 13 C -NMR spectroscopy.
Abstract: The reaction of norbornene (NBE) and norbornadiene (NBD) in the presence of seven-coordinate tungsten(II) and molybdenum(II) complexes of the [(CO) 4 M(μ-Cl) 3 M(SnCl 3 )(CO) 3 ] and [MCl(M′Cl 3 )(CO) 3 (NCMe) 2 ] (M=W, Mo; M′=Sn, Ge) types leads to ring-opening metathesis polymerization (ROMP) and to the formation of high molecular weight polymers The geometric structure of these polymers was determined by means of 1 H - and 13 C -NMR spectroscopy The monitoring of the reaction between cyclic olefins and the metal complex by means of 1 H -NMR spectroscopy allowed us to observe the coordination of NBD to metal atoms in the initiation step of the polymerization process Compounds of the [MCl(SnCl 3 )(CO) 3 (η 4 -NBD)] type prepared directly from [(CO) 4 M(μ-Cl) 3 M(SnCl 3 )(CO) 3 ] or [MCl(M′Cl 3 )(CO) 3 (NCMe) 2 ] (M=W, Mo) in the presence of an excess of NBD initiate the ROMP reaction immediately The detection of the first-formed products in the reaction between the metal complex and cyclic olefins provides valuable information concerning the nature of the initiating species

Journal ArticleDOI
TL;DR: Ruthenium-catalyzed cycloadditions of 2,3-disubstituted norbornadienes and 2,substitized norbornadiene with an alkyne were found to be highly chemo- and stereoselective with moderate level of regioselectivities and only small rate differences were observed with different substituents on the norbornadaene as discussed by the authors.

Journal ArticleDOI
TL;DR: The cobalt catalyzed neutral Diels-Alder reaction of various acyclic 1,3-dienes and norbornadiene with 1, 3-diynes can be controlled to give the 1:1 adduct, whereas the 1 : 2 adducts are only formed with sterically less hindered 1.3-Dienes as discussed by the authors.
Abstract: The cobalt catalyzed neutral Diels-Alder reaction of various acyclic 1,3-dienes and norbornadiene with 1,3-diynes can be controlled to give the 1:1 adduct, whereas the 1:2 adducts are only formed with sterically less hindered 1,3-dienes. With unsymmetrical 1,3-diynes the regiochemistry is mainly controlled by steric factors for unfunctionalized diynes, whereas the regiodirecting methoxymethyl substituent favors the Diels-Alder reaction at the closest triple bond. The combination of steric effects and the methoxymethyl substituent exclusively generates one of the two possible neutral Diels-Alder products. The mild oxidation of the dihydroaromatic products by stoichiometric amounts of DDQ, or alternatively under electrochemical regeneration of the spent oxidizing agent at the anode, generates phenylacetylene derivatives, from the 1:1 adduct, or biphenyl derivatives, from the 1:2 adducts respectively.

Journal ArticleDOI
TL;DR: An unprecedented endo-selective and regioselective intermolecular Pauson-Khand reaction takes place when heterobimetallic complexes derived from N-(2-alkynoyl)oxazolidinones or sultams are heated in the presence of norbornadiene.

Journal ArticleDOI
TL;DR: The biological activity against L 1210 and L1210/DDP cell lines of these compounds together with the behaviour of other organoplatinum complexes, [PtR(2)L(2)] (L( 2)=ethane-1,2-diamine (en) or cis-(NH(3))(2)) have been determined.

Journal ArticleDOI
TL;DR: Heterobimetallic?-alkyne complexes [?5-Cp(CO)2W(?-R1C2R2)Co (CO)3] are suitable substrates for the intermolecular Pauson-Khand reaction as discussed by the authors.

Journal ArticleDOI
TL;DR: The theoretical data correctly reproduce the experimental facial syn selectivity of norbornene and norbornadiene epoxidations and compare well with the experimental activation free energies of the peroxy acid epoxidation of all the olefins reported here.
Abstract: We studied, with the RB3LYP/6-311+G(d,p) method, the mechanism of peroxyformic acid epoxidation of norbornene, norbornadiene, tetramethylethene, and anti- and syn-sesquinorbornenes. The transition structures (TSs) for the reaction of tetramethylethene and norbornene show a perfect spiro geometry (the peroxy acid plane is perpendicular to the CC bond axis) with synchronous bond formation. Also three out of the four TSs of the norbornadiene reaction are spiro-like, but the highly asynchronous syn,endo-TS has a planar-like geometry. anti- and syn-sesquinorbornenes are substrates that, because of steric constraints, cannot easily accommodate spiro-like TSs. In fact, we managed to locate only a planar-like TS and a planar TS (the peroxy acid plane contains the CC bond axis), respectively, for these substrates. These planar TSs are “nonconcerted” since they are strongly unsymmetrical and only one of the C−O bonds of the oxirane ring is significantly formed. IRC analysis, while confirming that formation of one C...

Journal ArticleDOI
TL;DR: Two primary face difunctionalised α-cyclodextrins (α-CDs) bearing AC and AD-positioned triarylphosphite ligands have been synthesised and their ability to form large chelate rings has been evaluated as discussed by the authors.

Journal ArticleDOI
TL;DR: Poly(2-ethynylthiophene) was stereoregularly prepared with a Rh complex catalyst, [Rh(norbornadiene)Cl]2, to selectively produce the cis−transoid isomer in high yields when triethylamine was used a...
Abstract: Poly(2-ethynylthiophene) was stereoregularly prepared with a Rh complex catalyst, [Rh(norbornadiene)Cl]2, to selectively produce the cis−transoid isomer in high yields when triethylamine was used a...

Journal ArticleDOI
TL;DR: The calculation predicts symmetry breaking for this CoIn, the two ethylenes forming a rhombus Although this distortion is hindered in norbornadiene by ring strain, this coIn seems easily accessible as indicated by the short time found for passing through it.
Abstract: Excitation of norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) at 200 nm populates two states in parallel, the second ππ* state and a Rydberg state. We monitored both populations by transient nonresonant ionization. From the ππ* state the molecule relaxes in consecutive steps with time constants 5, 31 and 55 fs down to the ground-state surface, whereas the Rydberg population merges to the other path on the ππ* surface within 420 fs. The relaxation steps are discussed in terms of conical intersections (CoIns) between different surfaces. Information on them is inferred from known spectroscopy and, for the last CoIn, from published calculations on Dewar benzene→prismane conversion and on ethylene photodimerization for which norbornadiene with its two nonconjugated double bonds is a model. The calculation predicts symmetry breaking for this CoIn, the two ethylenes forming a rhombus. Although this distortion is hindered in norbornadiene by ring strain, this CoIn seems easily accessible as indicated by the short time (<55 fs) found for passing through it.

Journal ArticleDOI
TL;DR: In this paper, the initiation mechanism of this catalytic reaction by seven-coordinate molybdenum(II) compounds is proposed and the structure of a novel compound 3 was established by the single-crystal X-ray diffraction method.

Journal ArticleDOI
TL;DR: In this paper, the dominance of the through-space interaction between the two outermost π-orbitals of norbornadiene has been established from comparison of measured and calculated momentum distributions.

Journal ArticleDOI
TL;DR: In this article, a series of porphyrins with masked diene and dienophile functionality are described, and a collection of each of these reactive components is the basis for a library of building blocks which allow easy and simple entry to a wide and simple access to a variety of complex Porphyrin-containing superstructures.
Abstract: The synthesis and utility of a series of porphyrins with (masked) diene and dienophile functionality are described. The key porphyrin diene is synthesised from a sulfolenopyrrole by a 3+1 strategy. A range of Diels-Alder cycloadducts is readily accessed from the diene by mild thermal extrusion of sulfur dioxide from the sulfolenoporphyrin, which produces the reactive porphodimethylidene. Each of these cycloadducts is fused to the porphyrin nucleus through a cyclohexene ring thus retaining some conformational flexibility in the resultant structures. The structures can be rigidified by mild oxidation to the corresponding benzo-derivatives. Diels-Alder reaction of the porphyrin 1,3-diene resulting from the sulfolenoporphyrin with norbornadiene produces the norbornene derivative, which can serve as a dienophile or dipolarophile in subsequent cycloaddition reactions. Nevertheless, a preferred route to this structure is through a corresponding 1+3 route, where the norbornene component is part of the tripyrrane. Extension of the synthetic protocols allows ready access to a “mixed function” porphyrin, containing both diene and dienophile components. Likewise, the synthesis of a bis-norbornene porphyrin is described. A collection of each of these reactive components is the basis for a library of building blocks which allows easy and simple entry to a wide variety of complex porphyrin-containing superstructures.

Journal ArticleDOI
TL;DR: In this article, the pyridinophane ligand L-4 and the analogous macrocycle L-6 have been characterized, and the X-ray structures of these ligands are presented.
Abstract: (Diene)rhodium(I) and -iridium(I) derivatives of the pyridinophane ligand L-4 and the analogous macrocycle L-6 have been prepared and characterized [diene = cyclooctadiene (COD) or norbornadiene (NBD)]. In all of the complexes, the ligand is coordinated in a x(3)-(amine)(pyridine)(2) fashion; a dynamic process, believed to be concerted, exchanges free and coordinated amine groups. [(LIr)-Ir-4(COD)](+) can be protonated at the amine nitrogen atom. It reacts with H2O2, but only in the presence of acid, to give an oxocyclooctenyl complex, formally a 4-e(-) oxidation product. X-ray structures of [(LRh)-Rh-4(COD)]PF6, [(LRh)-Rh-6(COD)]PF6, [(LRh)-Rh-6(NBD)]PF6, [((LH)-H-4)Ir(COD)](BF4)(2), and [(LIr)-Ir-4(C8H11O)](PF6)(2) are presented.

Journal ArticleDOI
TL;DR: In this article, the authors presented the first comprehensive HREMS/DFT investigation into the complete valence electronic structure of norbornadiene (NBD), with significant results being obtained.
Abstract: Momentum Distributions (MDs), obtained using high-resolution electron momentum spectroscopy (HREMS), are reported for norbornadiene's 18 valence orbitals. Corresponding theoretical results, using generalized gradient approximation density functional theory (DFT) together with TZVP, DZVP, and DZVP2 basis functions and a plane wave impulse approximation to describe the ionization process, are also detailed. This work represents the first comprehensive HREMS/DFT investigation into the complete valence electronic structure of norbornadiene (NBD), with significant results being obtained. In particular, an exacting comparison between our experimental and theoretical MDs enables us to define the “optimum” basis for NBD, from those we studied. This “optimum” basis is then used to extract a wide range of NBD's important molecular property information, which are subsequently compared with the results of independent measurements and calculations. Agreement between our results and those from independent measurements ...

Journal ArticleDOI
TL;DR: For the binary liquid mixtures of norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) + benzene, + cyclohexane, + decane, or + carbon tetrachloride, the molar excess volumes were determined from density measurements by means of a vibrating glass tube densimeter at 293.15 K and 313.15K.
Abstract: For the binary liquid mixtures of norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) + benzene, + cyclohexane, + decane, or + carbon tetrachloride, the molar excess volumes were determined from density measurements by means of a vibrating glass tube densimeter at 293.15 K and 313.15 K, and the molar excess enthalpies were measured by means of a flow microcalorimeter of Picker type at 293.15 K. All measurements were performed at atmospheric pressure.

Journal ArticleDOI
TL;DR: In this article, normal alkylpropiolate was polymerized with [Rh(norbornadiene)Cl] 2 catalyst in methanol solvent to produce poly( n -butylpropiolates), (PBPA) polymer called polyacetylene esters in relatively high yields.

Journal ArticleDOI
TL;DR: In this article, the Paterno−Buchi cycloadducts of benzoquinone with norbornadiene or quadricyclane stem from a triplet biradical 3III with a norborn...
Abstract: Chemically induced dynamic nuclear spin polarizations (CIDNP) in the Paterno−Buchi cycloadducts of benzoquinone with norbornadiene or quadricyclane stem from a triplet biradical 3III with a norborn...