Showing papers on "Norbornadiene published in 1981"

Photoinduced electron-transfer reactions. Radical cations of norbornadiene and quadricyclene

Abstract: A chemically induced nuclear spin polarization study was made to elucidate the structure of the radical cations of norbornadiene (1) and quadricyclene (2) and to ascertain whether they are two discrete species or a single homallylic structure. Photoreaction of chloranil was used. Results indicate that two discrete radical cations are generated by electron transfer from 1 and 2, and that each must have a lifetime of at least several nanoseconds to explain the generation of nuclear spin polarization. One cation gives rise to a polarized rearrangement product (1) while the other does not lead to a polarized 2. (DLC)

The Rhodium Complex-catalyzed Synthesis of Quinolines from Aminoarenes and Aliphatic Aldehydes

Abstract: A variety of aminoarenes react with aliphatic aldehydes in the presence of a catalytic amount of a rhodium complex and an excess amount of the corresponding nitroarenes at 180 °C to give 2-alkyl- and 2,3-dialkyl-substituted quinolines in excellent yields. Among the rhodium complexes examined, [Rh(norbornadiene)Cl]2 exhibits the highest activity as a catalyst. Thus, 2-methyl-, 2-ethyl-3-methyl-, 2-propyl-3-ethyl-, and 2-butyl-3-propylquinoline derivatives are readily obtained from aminoarenes and ethanal, propanal, butanal, and pent-anal respectively.

Exploitation of solar energy storage systems. Valence isomerization between norbornadiene and quadricyclane derivatives

Abstract: Use of copper(I)-nitrogen ligand catalysts such as Ph/sub 3/PCuCl.bpy, Ph/sub 3/PCuCl.phen, Ph/sub 3/PCuCl.phtha, and Ph/sub 3/PCuBr.py enables the photochemical isomerization of norbornadiene to quadricyclane to be performed at a longer wavelength than 350 nm, at which CuCl catalyst itself cannot induce such an isomerization. Among the norbornadiene derivatives bearing various chromophores, 3-(phenylcarbamoyl)norbornadiene-2-carboxylic acid undergoes a facile and quantitative isomerization into the corresponding quadricyclane derivative in sunlight. The back-isomerization of quadricyclane to 3-(phenylcarbamoyl)norbornadiene-2-carboxylic acid proceeds quantitatively by use of catalytic amounts of Rh/sub 2/(CO)/sub 4/Cl/sub 2/.

Application of the water-gas shift reaction. I. Hydrogenation and hydroformylation reactions of olefins with carbon monoxide and water catalyzed by rhodium phosphine complexes.

Abstract: The hydrogenation of methyl crotonate with CO and H2O is efficiently catalyzed by RhH2(O2COH)[P(i-Pr)3]2 or [RhCl(C7H8)]2/P(i-Pr)3/n-BuLi (C7H8=norbornadiene). Both catalyst precursors are shown to form the same active species; transRh(OH)(CO)[P(i-Pr)3]2. The catalytic activity of the system ([RhCl(C7H8)]2/phosphine/n-BuLi) increases with increase of the basicity of the phosphine ligands (phosphine=P(i-Pr)3>P(n-Bu)3>PPh(i-Pr)2>PPh2(i-Pr)>PPh3). This reaction is also applicable to the hydrogenation of the C=C bond of electronwithdrawing olefins and the C=O bond of ketones and aldehydes. Interestingly, the catalysis for the C=C bond, to which less electron-withdrawing groups are attached, gives dominantly aldehydes due to hydroformylation. The mechanism is also discussed.

119Sn‐ and 31P‐NMR. Spectroscopy of the 5‐coordinate complexes [Rh (SnClnBr(3−n)) (norbornadiene) (tertiary phosphine)2]

Abstract: The products of the reaction of [RhCl (NBD)]2 (NBD = norbornadiene), with four equivalents tertiary phosphine and two equivalents of tin (II) bromide have been studied by 119Sn- and 31P-NMR. spectroscopy. The solution data suggest that halogen scrambling occurs during the preparation and results in a mixture of complexes containing SnBr3, SnClBr2, and SnCl2Br and SnCl3 ligands, and this is confirmed by independent synthesis of the SnCl3 and SnBr3 complexes. The metalmetal coupling constants, 1J (119Sn, 103Rh), vary from 452 to 580 Hz and are linearly related to: (a) δ(119Sn) in the complexes [Rh (SnClnBr(3-n))NBD (PEtPh2)2] and (b) the sum of the Pauling electronegativities for the halogens on tin.

Highly efficient valence isomerization between norbornadiene and quadricyclane derivatives under sunlight.

Abstract: 3-Phenylcarbamoyl-2,5-norbornadiene-2-carboxylic acid (1b) undergoes a facile and quantitative isomerization into the corresponding quadricyclane derivative (2b) under sunlight. The back isomerization of 2b to 1b proceeds quantitatively by the use of catalytic amounts of Rh2(CO)4Cl2.

Preparation and properties of some cationic norbornadiene rhodium(I) complexes with triarylphosphines

Abstract: The synthesis of [Rh(NBD){P(p-RC6H4)3}2]A complexes (A=ClO 4 − or BPh 4 − ; R=Cl, F, Me or MeO) is described. Treatment of these complexes with molecular hydrogen leads to the isolation of [RhH2{P(p-RC6H4)3}2(OCMe2)2]ClO4 or Rh{P(p-RC6H4)3}2PhBPh3. These latter complexes contain tetraphenylborate coordinated to the metalvia arene interaction. [Rh(CO)3{P(p-RC6H4)3}2]ClO4 complexes have been isolated by carbonylations. The use of these complexes as homogeneous hydroformylation catalysts is also briefly investigated.

Catalytic hydrogenation of soybean oil with Rh(l) dihydride complexes as catalysts

Abstract: Cationic rhodium(I) complexes of the type [NBD Rh L2]+[C1O4]− (NBD = norbornadiene and L = diphenylphosphinoethane or triphenylphosphine) have been studied as catalysts for the hydrogenation of soybean oil. These catalysts give a good yield of products with cis-configuration. Indeed, hydrogenation could be performed under mild conditions (30 C, 1 atm hydrogen pressure) to an iodine value of 80 with not more than 12% oftrans monoenes and only 5% conjugated isomers formed. The results obtained are interpreted on the basis of the equilibrium H2RhL n + ⇌HRhLn+H+. By the addition of acid (HClO4 ) the bishydrido form of the catalyst could be studied. With this system only small amounts of trans monoenes were formed and no othertrans isomers could be detected. By the addition of a base such as triethylamine, the monohydridic form of the catalyst could be studied. In contrast to the bishydrido complex, this system gave large amounts oftrans monoenes, together withcis-trans andtrans-trans forms of the 18:2 acid. With both forms of the catalyst system, conjugated isomers were formed.

Formation and thermal cleavage reactions of the cycloadduct of 9,10-dimethylanthracene and nitrosyl cyanide

Abstract: Nitrosyl cyanide and 9,10-dimethylanthracene (DMA)(2) reacted at –25 °C to form the crystalline cycloadduct, 9,10-dihydro-9,10-(N-cyanoepoxyimino)-9,10-dimethylanthracene (1). The adduct (1) decomposed in the presence of the conjugated diene thebaine (3), to form DMA (2) and the adduct (4) of nitrosyl cyanide and thebaine. First-order kinetics, k= 6.9 × 10–5s–1, were observed for the release of DMA in benzene at 40 °C, consistent with slow dissociation of the adduct (1) followed by rapid capture of nitrosyl cyanide by thebaine. A similar first-order rate, k= 6.8 × 10–5s–1, was observed for the reaction of the adduct (1) and triphenylphosphine (2 mol equiv.) under the same conditions, the products being DMA, triphenylphosphine oxide, and triphenylphosphine N-cyanoimide (5). The reactions of nitrosyl cyanide, generated thermally from the adduct (1), were studied with a range of dienes. The conjugated dienes, N-cyanomethyl-N-northebaine (3; NCH2CN replacing NMe), trans,trans-1,4-diphenylbuta-1,3-diene (6; R = H), and ergosteryl acetate (11) all gave the expected cycloadducts (3,6-dihydro-2H-1,2-oxazines). Norbornadiene gave the tetracyclic adduct (10) arising from 1,4-conjugate addition of nitrosyl cyanide. The reactions of the adduct (1) with tetraphenylcyclopentadienone (14), 1,3-diphenylisobenzofuran (18), 2-methyl-1,3-diphenylisoindole (23), diazofluorene (24), and diphenyldiazomethane all took a more complex course leading in each case to the formation of an N-cyano-ketimine (alkylidene-cyanamide)

Crystal Structure and van der Waals Energy Study of the 2:1 Inclusion Compound between Deoxycholic Acid and Norbornadiene

Abstract: The crystals are orthorhombic, space group P2~2t21, with a = 27.125 (8), b = 13.456 (4), c = 14.212 (5) A, Z = 4. The structure has been refined to R = 0.11 and R w = 0.14 for 2451 observed reflections with I > 3o(1). The crystal structure is characterized by an assembly of bilayers which are slightly different from those of other orthorhombic phases studied so far. The section of the cavities in which the norbornadiene is accommodated is almost square, so that molecules or substituents of approximately spherical shape can be occluded. Van der Waals energy calculations allowed the location of the guest molecules which mainly interact with methyl groups.

Frontier-controlled cycloaddition reactions of cyclopentadienones having electron-donating or -attracting substituents: configuration of adducts and kinetic studies

Abstract: The stereochemistry of the main adducts resulting from the cycloadditions of 2,5-dimethoxycarbonyl- and 2,5-diethyl-3,4-diphenylcyclopentadienones [CPC (1a) and EPC (1b)] with para-substituted styrenes (2a–h), norbornadiene (7), norbornene (8), 1,4-dihydro-1,4-epoxynaphthalene (9), maleic anhydride (10), and N-phenylmaleimide (11), was established as having the endo configuration. In order to define the substituent effects on the rate of the Diels–Alder reaction, a kinetic study of the reactivities of (1a, b) with a series of styrenes (2a–h) was carried out. The log k/kH values for the cycloadditions of (1a) with (2a–h) were correlated with Okamoto–Brown's σp+ constants and the ρ value was –0.941. This result suggests that the cycloaddition is classified as a Diels–Alder reaction with inverse electron demand. By contrast, in the correlation for the cycloaddition of (1b) with (2a–h), two lines with markedly different slopes were observed, which can be ascribed to a Diels–Alder reaction with neutral electron demand. The initial cycloadditions of (1a) and (1b) with tropone (29) gave the [4 + 6]π adducts (32a,b). Subsequently the adduct (32b) underwent oxy-Cope rearrangement to (35). The cycloadditions of (1a) and (1b) with 2-chlorotropone also gave oxy-Cope-type rearrangement products (34a,b).

Einfache Synthese von Nortricyclylchlorid

Abstract: Simple Synthesis of Nortricyclyl Chloride In the presence of titanium tetrachloride the mixture of 5-exo-chloro-2-norbornene (2) and nortricyclyl chloride (3), obtained by HCl addition to norbornadiene (1), reacts completely to form 3. Thus, a simple synthesis of 3 is possible for the first time.