Reaction Of Norbornene Research Articles

Synthesis and Evaluation of Ruthenium 2‐Alkyl‐6‐mercaptophenolate Catalysts for Olefin Metathesis

A series of ruthenium carbene catalysts containing 2‐sulfidophenolate bidentate ligand with an ortho‐substituent next to the oxygen atom were synthesized. The molecular structure of ruthenium carbene complex containing 2‐isopropyl‐6‐sulfidophenolate ligand was confirmed through single crystal X‐ray diffraction. An oxygen atom can be found in the opposite position of the N‐heterocyclic carbene (NHC) based on the steric hindrance and strong trans‐effects of the NHC ligand. The ruthenium carbene catalyst can catalyze ring‐opening metathesis polymerization (ROMP) reaction of norbornene with high activity and Z‐selectivity and cross metathesis (CM) reactions of terminal alkenes with (Z)‐but‐2‐ene‐1,4‐diol to give Z‐olefin products (Z/E ratios, 70:30–89:11) in low yields (13%–38%). When AlCl3 was added into the CM reactions, yields (51%–88%) were considerably improved and process becomes highly selective for E‐olefin products (E/Z ratios, 79:21–96:4). Similar to other ruthenium carbene catalysts, these new complexes can tolerate different functional groups.

A Domino Ring‐Closure Followed by Retro‐Diels–Alder Reaction for the Preparation of Pyrimido[2,1‐a]isoindole Enantiomers

A simple method was developed to prepare pyrimido[2,1‐a]isoindole derivatives by using di‐endo‐ and di‐exo‐ethyl 3‐aminobicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate enantiomers as chiral sources. The method is based on a domino ring‐closure reaction of norbornene 2‐aminohydroxamic acid followed by microwave‐induced retro‐Diels–Alder reaction. In the case of enantiomeric starting substances, the chirality is transferred from norbornene derivatives to pyrimido[2,1‐a]isoindoles. The configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy [based on 2D NOE cross‐peaks and 3JH,H coupling constants] and X‐ray crystallography.

Atmospheric and high pressure ene reaction of norbornene with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione

Thermodynamic and activation parameters (enthalpy, entropy, and volume) have been determined from the pressure and temperature dependences of the rate of the reaction of norbornene with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione in toluene, which is accompanied by Wagner-Meerwein rearrangement. The enthalpy of the reaction in 1,2-dichloroethane has been determined by calorimetry. The obtained data correspond to a weakly polar transition state.

Products of direct hydroalkoxylation of norbornene with alcohols over H-beta zeolite catalyst

The reaction of direct hydroalkoxylation of norbornene in the presence of H-beta zeolite catalyst has been studied. It has been found that the selectivity for exo-alkoxynorbornanes of the reaction of norbornene with monohydric alcohols (saturated, unsaturated, or aromatic) reaches 98% at a conversion of 78–98% of the unsaturated compound. The reaction of norbornene with diols (ethylene glycol and 2-butene-1,4-diol) in the presence of H-beta zeolite affords mono- and diethers, whose yield and ratio can be controlled by varying reaction parameters.

ChemInform Abstract: Iridium‐Catalyzed Intermolecular Asymmetric Hydroheteroarylation of Bicycloalkenes.

AbstractThe reaction of norbornene (II) and norbornadiene (X) with indoles, thiophenes, furans and pyrroles proceeds with moderate to high enantioselectivities.

Stannylation of unsaturated carbon–carbon bonds by tin tetrachloride

The reactions of tin tetrachloride and four terminal alkynes (PhC CH, t BuC CH, n BuC CH, HOCH 2C CH), norbornene, and norbornadiene in dichloromethane or chloroform solution lead to the formation of stannylation products, which were characterized by 1H, 13C and 119Sn NMR spectroscopy. Virtually complete α-regioselectivity was obtained in reaction of all four alkynes without any effect of the relative steric bulk of the substituent R at the triple bond of alkyne RC β C αH. The reaction of norbornene and norbornadiene with SnCl 4 is stereoselective, giving an exo stannylation product.

Rh(I)-Catalyzed Carbonylative Cyclization Reactions of Alkynes with 2-Bromophenylboronic Acids Leading to Indenones

The Rh-catalyzed reaction of alkynes with 2-bromophenylboronic acids involves carbonylative cyclization to give indenones. The key steps in the reaction involve the addition of an arylrhodium(I) species to an alkyne and the oxidative addition of C-Br bonds on the adjacent phenyl ring to give vinylrhodium(I) species II. The regioselectivity depends on both the electronic and the steric nature of the substituents on the alkynes. A bulky group and an electron-withdrawing group favor the -position of indenones. In the case of silyl- or ester-substituted alkynes, the regioselectivity is extremely high. The selectivity increases in the order SiMe3 > COOR >> aryl >> alkyl. The reaction of norbornene with 2-bromophenylboronic acids under 1 atm of CO gives the corresponding indanone derivative. The reaction of alkynes with 2-bromophenylboronic acids under nitrogen gives naphthalene derivatives, in which two molecules of alkynes are incorporated. A vinylrhodium complex similar to II can also be generated by a different route by employing 2-bromophenyl(trimethylsilyl)acetylene and arylboronic acids in the presence of Rh(I) complex as the catalyst, resulting in the formation of indenones. The reaction of 1-(2-bromophenyl)-hept-2-yn-1-one with PhB(OH)2 in the presence of Rh(I) complex also resulted in carbonylative cyclization to give an indan-1,3-dione derivative.

Reactions of Gold(III) Oxo Complexes with Cyclic Alkenes

An auraoxetane , obtained from the reaction of norbornene with a gold( III ) oxo complex, has been isolated and fully characterized (see structure). Action of the olefin leads to elimination of the epoxide from the auraoxetane.

One-pot sequential Pauson–Khand reaction – transfer hydrogenation

The Pauson–Khand reaction of norbornene (1) and phenylacetylene (2) and subsequent RuCl2(PPh3)3-catalyzed transfer hydrogenation of the resulting enone (3) can be carried out in a one-pot sequence if the base is added after an induction period. The desired ketones (4a, 4b) were obtained in good yield as a mixture of diastereomers (diastereomeric ratio (dr.) 58:42). The relative rates of both the Pauson-Khand reaction and the transfer hydrogenation are decreased by a factor of 2 in the sequence, as compared with the isolated reactions.Key words: Pauson–Khand reaction, transfer hydrogenation.

Ring-opening metathesis polymerization of norbornene and norbornadiene by tungsten(II) and molybdenum(II) complexes

The reaction of norbornene (NBE) and norbornadiene (NBD) in the presence of seven-coordinate tungsten(II) and molybdenum(II) complexes of the [(CO) 4M(μ-Cl) 3M(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) 4M(μ-Cl) 3M(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.

ChemInform Abstract: Ground‐ and Excited‐State Reactions of Norbornene and Isomers: A CASSCF Study and Comparison with Femtosecond Experiments.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Thermal fragmentation reactions of 1,4,2-dithiazines and 1,4,2,5-dithiadiazines in the presence of dienophiles: synthesis of 1,4-dithiine derivatives. X-Ray crystal structures of a 1,4,2-dithiazine 1,1-dioxide and a 1,4,2,5-dithiadiazine derivative

The reaction of 5,6-dimethyl-3-(4-bromophenyl)-1,4,2-dithiazine 1b with dimethyl acetylenedicarboxylate (DMAD) at 180 °C in o-dichlorobenzene affords a mixture of thiophene derivative 5 and isothiazole derivative 6: the former probably via the zwitterionic adduct 3 and dithiine derivative 4, neither of which are isolable; the latter by sulfur extrusion from 1b. Reaction of norbornene with 1b affords dithiine derivative 7. Oxidation of 1b with meta-chloroperoxybenzoic acid yields the 1,1-dioxide derivative 8, the X-ray crystal structure of which is reported. The efficient synthesis of 3-aryl-6-methylthio-1,4,2,5-dithiadiazine derivatives 12a–c by ring expansion of 1,4,2-dithiazolium salts 11a–c with an iodine–ammonia reagent is described. Reaction of 12c with DMAD at 180 °C affords the stable dithiine derivative 14, probably via the intermediate 1,4,2-dithiazine 13. Electrochemical oxidation of 12a–c is irreversible, yielding 1,4,2,5-dithiadiazinium cation radicals at potentials [E ox = 1.55–1.73 V (vs. Ag/AgCl)] which are sensitive to the electronic nature of the para-substituent on the aryl ring. The X-ray crystal structure of 12b is reported.

Femtosecond dynamics reveal two paths in Diels-Alder reaction

In work that opens a window to of most important reactions in organic chemistry, researchers at California Institute of Technology have studied realtime dynamics of retro-Diels-Alder reactions of norbornene and norbornadiene. An intermediate detected by ultrafast laser techniques and femtosecond-resolved mass spectrometry suggests that both concerted and nonconcerted routes are available for retro (reverse) and thus for forward Diels-Alder cycloaddition as well. The Caltech researchers, led by chemistry and physics professor Ahmed H. Zewail, have taken on one of classic problems of physical organic chemistry—the timing of bonding changes in Diels-Alder reaction, says Kendall N. Houk, a chemistry professor at University of California, Los Angeles. It is a blast to watch reaction happen and to see if intermediates are there, and if so, how long they stick around. The work also demonstrates the power of femtosecond techniques to detect transient intermed...

Retro-Diels−Alder Femtosecond Reaction Dynamics

In this communication, we present our first femtosecond (fs), real-time studies of the retro-Diels-Alder reactions of norbornene (NB) and norbornadiene (NBD), products of the cycloaddition of cyclopentadiene with ethylene and acetylene, respectively. The reaction path, together with transition state (TS) structures, is displayed in Figure 1 (bottom). The experiments were designed with the following considerations in mind. First, the reactions were studied in a molecular beam in order to isolate the elementary processes, free of solvent perturbations. Second, we examined the dynamics of the reaction from a well-defined initial geometry, a precursor of Diels-Alder products.

ChemInform Abstract: The Reaction of Norbornene with Selenium(II) and Selenium(IV) Fluorides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The reaction of norbornene with selenium(II) and selenium(IV) flourides

PhSeF adds to norbornene predominantly in a trans-manner to give non-rearranged 2, 3-selenofluorination adducts, 4 and 5, corresponding to exo- and endo-attack. In contrast, PhSeF 3 gives mainly the products of cis-exo-addition, 6, along with the Wagner-Meerwein rearrangement product, 7.

Diastereofacial selectivity in 1,3‐dipolar cycloadditions to cyclobutens. 8. HF/3–21G transition structures of the reactions of formonitrile oxide with CIS‐3,4‐dichlorocyclobutene and norbornene

AbstractA transition structure for the syn and anti attack of formonitrile oxide on both cis‐3,4‐dichlorocyclobutene and norbornene was obtained using HF/3–21G method. These calculations correctly predict dominance of the syn attack in the reaction of dichlorocyclobutene and 100% syn selectivity, with respect to the methano bridge, in the reaction of norbornene. Analysis of the activation energy shows that the inherent facial bias of dichlorocyclobutene is reflected, at the transition state, in a complex way in the deformation energy of both dichlorocyclobutene and formonitrile oxide and in the interaction energy between them. With norbornene the out‐of‐plane deformation energy of the olefinic hydrogens clearly emerges as the major factor in controlling facial selectivity.

The partial oxidation of norbornene over a silver catalyst under steady state conditions

The continuous oxidation of norbornene (C7H10) by molecular oxygen over a silver catalyst at 500–573 K has been investigated. In contrast to that observed during the temperature programmed reaction of norbornene and oxygen adsorbed on Ag(110) no norbornene epoxide is formed. Instead benzene is the sole partial oxidation product. A stable selectivity of 20 to 25% with fractional conversions up to 0.8 at 573 K could be obtained by inclusion of 15 to 30 ppm dichloroethane in the feed. Separate experiments withexo-norbornene epoxide showed that in the absence of oxygen it was almost completely isomerised to 3-cyclohexene-1-carboxyaldehyde with production of lesser amounts of norcamphor and norbornene. With oxygen present carbon dioxide and small amounts of benzene were also produced. It is concluded that norbornene epoxide cannot be a gas phase intermediate in the production of benzene from norbornene.

Chain-transfer agents for living ROMP [Ring-Opening Metathesis Polymerization] reactions of norbornene

Chain-transfer agents for living ROMP [Ring-Opening Metathesis Polymerization] reactions of norbornene

A Facile, One-Step, Stereoselecttve Synthesis of Norbornane-2-Carboxaldehyde

Abstract A facile, one-step, stereoselective synthesis of norbornane-2-carboxaldehyde by reaction of norbornene with potassium tetracarbonylhydridoferrate is described.