2505-03-5Relevant articles and documents
Selective ethylene oligomerization with chromium complexes bearing pyridine-phosphine ligands: Influence of ligand structure on catalytic behavior
Yang, Yun,Gurnham, Joanna,Liu, Boping,Duchateau, Robbert,Gambarotta, Sandro,Korobkov, Ilia
, p. 5749 - 5757 (2015/02/19)
Chromium complexes bearing a series of pyridine-phosphine ligands have been synthesized and examined for their catalytic behavior in ethylene oligomerization. The choice of solvent, toluene versus methylcyclohexane, shows a pronounced influence on the catalytic activity for all these complexes. Variations of the ligand system have been introduced by modifying the phosphine substituents affecting ligand bite angles and flexibility. It has been demonstrated that minor differences in the ligand structure can result in remarkable changes not only in catalytic activity but also in selectivity toward α-olefins versus polyethylene and distribution of oligomeric products. Ligand PyCH2N(Me)PiPr2, in combination with CrCl3(THF)3 afforded selective ethylene tri- and tetramerization, giving 1-hexene and 1-octene with good overall selectivity and high purity, albeit with the presence of small amounts of PE.
Ruthenium(IV)-catalyzed markovnikov addition of carboxylic acids to terminal alkynes in aqueous medium
Cadierno, Victorio,Francos, Javier,Gimeno, Jose
experimental part, p. 852 - 862 (2011/04/15)
The dimeric bis(allyl)ruthenium(IV) complex [{RuCl(μ-Cl)( η3:η3-C10H16)}2] (C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl) (5) and several mononuclear species trans-[RuCl2(η3: η3-C10H16)(L)] (L = two-electron-donor ligand) (6) derived from 5 have been checked as catalysts for the addition of carboxylic acids onto terminal alkynes using water as a green reaction medium. The best results in terms of activity and regioselectivity were obtained with the mononuclear derivative trans-[RuCl2(η3: η3-C10H16)(PPh3)] (6a), which was able to promote the selective Markovnikov addition of both aromatic and aliphatic carboxylic acids to a large variety of terminal alkynes, enynes, and diynes as well as propargylic alcohols. In this way, a wide number of enol esters and β-oxo esters could be synthesized in moderate to good yields under mild conditions (60 °C) in an aqueous medium.
Six- vs seven-membered ring formation from the 1- bicyclo[4.1.0]heptanylmethyl radical: Synthetic and ab initio studies
Kantorowski, Eric J.,Eisenberg, Shawn W. E.,Fink, William H.,Kurth, Mark J.
, p. 570 - 580 (2007/10/03)
The viability of utilizing 1-bicyclo[4.1.0]heptanylmethyl radical (3) to serve as a progenitor of seven-membered carbocycles was examined. Rate constants for the rearrangement of this radical to 3-methylenecycloheptyl radical (4) and 2-methylenecyclohexyl-1-methyl radical (6) were measured using the competition method of 3 with thiophenol over the temperature range of -75 to 59 °C. Arrhenius functions were calculated for the conversions of 3 to 4 and 3 to 6 and found to be log(k/s-1) = (12.38 ± 0.20) - (5.63 ± 0.23)/θ and log(k/s-1) = (11.54 ± 0.32) - (5.26 ± 0.37)/θ, respectively. The rate constants for these conversions at 25 °C are 1.86 x 108 s-1 and 5.11 x 107 s-1, respectively. Hence, the seven-membered ring-expanded carbocycle is formed 3.6 times faster at 25 °C than the nonexpanded species. This suggests that the 1-bicyclo[4.1.0]heptanylmethyl radical system may be synthetically useful in seven-membered ring-forming methodology. Preliminary theoretical examination of this radical system qualitatively predicted the experimentally determined energies of activation: PMP4/6-31G*//HF/6-31G*ΔE(a) (3 → 6 - 3 → 4) = 3.0 kcal/mol with zero point energy correction. The HF/6-31G* optimized reaction coordinate stationary points suggest cyclopropyl substituent eclipsing interactions play an important role in determining the kinetic outcome of these rearrangements.
Cyclopropylcarbinyl radical-mediated ring expansion to seven-membered carbocycles
Kantorowski, Eric J.,Borhan, Babak,Nazarian, Saman,Kurth, Mark J.
, p. 2483 - 2486 (2007/10/03)
Radical-mediated ring expansion methodology is presented wherein 7- membered carbocycles can be prepared from the corresponding xanthate derivatives of bicyclo[4.1.0]heptan-1-methanol. In certain systems, an intermediate cycloheptyl radical appears to be
CLEAVAGE OF (3-CHLORO-2-METHYLENECYCLOALKYL)PALLADIUM CHLORIDE DIMERS: FORMATION OF OLEFINS AND α-METHOXYOLEFINS
Donaldson, William A.
, p. 2901 - 2908 (2007/10/02)
The cleavage of the title compounds (7) in methanolic potassium hydroxide gives mixtures of olefins and α-methoxyolefins in good yields.The ratio of the products is dependent on the size of the carbocyclic ring.The mechanism proposed involves cleavage of 7 to the corresponding allylic chloride (8).Solvolysis of the chloride gives the α-methoxyolefin.Alternatively, oxidative addition of 8 to Pd(O) generates a new ?-allyl complex which affords the olefin product upon subsequent cleavage.
REACTIVITY OF (3-CHLORO-2-METHYLENECYCLOALKYL)PALLADIUM CHLORIDE DIMERS: PD-ALLYL CLEAVAGE, SYNTHESIS OF (+/-)-13-METHYLTRIDECANOLIDE
Donaldson, William A.,Taylor, Barbara S.
, p. 4163 - 4166 (2007/10/02)
The reactions of the title compounds under cleavage conditions affords the corresponding cycloalkenes as the major product.This methodology was used in the synthesis of 13-methyltridecanolide from cyclododecene.
Photochemistry of Alkenes. 9. Medium-sized cycloalkenes
Kropp, Paul J.,Mason, J. Derek,Smith, Gardiner F. H.
, p. 1845 - 1849 (2007/10/02)
The behavior of three medium-sized cycloalkenes cyclooctene (10), cyclodecene (17) and cyclododecene (21) on direct irradiation in pentane and methanol solution has been studied.The results are summarized in Tables 1-3.Irradiation of medium-sized cycloalkenes is a convenient procedure for the preparation of bicyclic products (cf. 13, 14, 19, 20 and 23) through transannular insertion reactions of carbene intermediates (cf. 11, 18, and 22) thought to arise from rearrangement of the 1 state via a 1,2-hydrogen shift.The formation of trans-decalin (20) is in contrast to the reported formation of the cis isomer on base-initiated decomposition of the corresponding tosylhydrazone.None of the three cycloalkenes 10, 17, or 21 underwent competing nucleophilic trapping of the 1 state in methanol, in contrast with other alkenes previously studied.However, cyclododecene (21) afforded the methyl ether 25, which apparently resulted from protonation of the 1(?,?*) state, and the epoxide 26, which is thought to arise from electron transfer to oxygen by the 1 state followed by protonation of the resulting superoxide ion and oxidation of unreacted cyclododecene (21).
