3061-36-7Relevant articles and documents
Time-Reverse ODESSA. A 1D Exchange Experiment for Rotating Solids with Several Groups of Equivalent Nuclei
Reichert,Zimmermann,Tekely,Poupko,Luz
, p. 245 - 258 (1997)
A one-dimensional exchange experiment is proposed for magic-angle-spinning samples with several groups of equivalent nuclei undergoing internal exchange, such as pure reorientation, as opposed to mutual exchange. The method, which we term time-reverse ODESSA, is an extension of the recently proposed 1D ODESSA experiment for a single group of exchanging nuclei. When several different groups of spins are present, as is usually the case for carbon-13 in polymers and molecular crystals, the normal ODESSA spectrum yields phase-twisted spectra which are difficult to analyze quantitatively. This problem is solved in the time-reverse ODESSA experiment which yields pure absorption spectra for all families of side bands, as long as only internal exchange need be considered. The experiment consists of the usual three pulse sequence of 2D exchange, P1 - t1 - P2 - τm -P3 - t2 (acquisition), except that the evolution time is fixed at half a rotation period, t1 = TR/2, the mixing time is set to an odd number of half rotation periods, τm = (2G - 1)TR/2, and the acquisition starts at t2 = TR/2 after the detection pulse, P3. The method is demonstrated using the carbon-13 spectra of dimethyl sulfone and an enriched sample of tropolone, and is applied to the study of the π flip of the inner benzene ring of 1,4-diphenoxybenzene. The scope and limitations of the method are discussed.
NMR and DFT studies on persistent carbocations derived from benzo[kl]xanthene, dibenzo[d,d′]benzo[1,2-b:4,3-b′]difuran, and dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran in superacidic media
Okazaki, Takao,Nakagawa, Madoka,Futemma, Takeshi,Kitagawa, Toshikazu
, p. 107 - 111 (2016/02/03)
Persistent carbocations generated by the protonation of hetero-polycyclic aromatic compounds with oxygen atom(s) were studied by experimental NMR and density function theory calculations. Benzo[kl]xanthene (1), dibenzo[d,d′]benzo[1,2-b:4,3-b′]difuran (2), and dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran (3) were synthesized by the annulation of arenediazonium salts. Compound 1 in FSO3H-SbF5 (4:1)/SO2ClF and 3 in FSO3H-SbF5 (1:1)/SO2ClF ionized to 1aH+ with protonation at C(4) and to 3aH+ with protonation at C(6), and these cations were successfully observed by NMR at low temperatures. The density function theory calculations indicated that 1aH+ and 3aH+ were the most stable protonated carbocations and that 2 should ionize to 2aH+ with protonation at C(6). According to the changes in 13C chemical shifts (Δδ13C), the positive charge was delocalized into the naphthalene unit for 1aH+, into one benzo[b,d]furan unit for 2aH+, and into one benzo[b,d]furan unit for 3aH+. The most stable persistent cations derived from the title compounds, 1-3, were found to be 1aH+ with protonation at C(4), 2aH+ with protonation at C(6), and 3aH+ with protonation at C(6) by experimental and theoretical methods.
Highly active recyclable heterogeneous Pd/ZnO nanoparticle catalyst: Sustainable developments for the C-O and C-N bond cross-coupling reactions of aryl halides under ligand-free conditions
Hosseini-Sarvari, Mona,Razmi, Zahra
, p. 44105 - 44116 (2014/12/10)
Efficient Pd supported on ZnO nanoparticles for the ligand-free O-arylation and N-arylation of phenols and various N-H heterocycles with aryl chlorides, bromides, and iodides were readily synthesized and characterized. The amount of palladium on ZnO is 9.84 wt% (0.005 g of the catalyst contains 462 × 10-8 mol% of Pd) which was determined by ICP analysis. This nano sized Pd/ZnO with an average particle size of 20-25 nm and specific surface area 40.61 m2 g-1 was used as a new reusable heterogeneous catalyst for the formation of C-O and C-N bonds in organic synthesis. This protocol gives the arylated product in satisfactory yields without any N2 or Ar flow. The catalyst can be recovered and recycled several times without marked loss of activity.
FLAME RETARDANT HALOGENATED PHENYL ETHERS
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, (2011/08/06)
A halogenated non-polymeric phenyl ether is described having the general formula (I): wherein each X is independently Cl or Br, n is an integer of 1 or 2, each m is independently an integer of 1 to 5 and each p is independently an integer of 1 to 4, provided that, when X is Cl, the total amount halogen in the ether is from about 50 to about 65 wt % and when, X is Br, the total amount halogen in the ether is from at least 70 wt % to about 79 wt %.
Ligand-free highly effective iron/copper co-catalyzed formation of dimeric aryl ethers or sulfides
Qu, Xiaoming,Li, Tingyi,Zhu, Yan,Sun, Peng,Yang, Hailong,Mao, Jincheng
supporting information; experimental part, p. 5043 - 5046 (2011/08/22)
Highly selective coupling of diiodoarenes with phenols or phenthiols can be performed by using a low-cost, benign character and readily available Fe/Cu catalytic system in the absence of ligands. It is noteworthy that the desired dimeric aryl ethers or sulfides could be obtained in high yields by coupling between diiodoarenes and phenols, or diphenols with aryl iodides. The Royal Society of Chemistry 2011.
Recyclable heterogeneous copper oxide on alumina catalyzed coupling of phenols and alcohols with aryl halides under ligand-free conditions
Swapna, Kokkirala,Murthy, Sabbavarapu Narayana,Jyothi, Mocharla Tarani,Nageswar, Yadavalli Venkata Durga
supporting information; experimental part, p. 5978 - 5988 (2011/10/05)
An efficient alumina-supported CuO-catalyzed O-arylation of phenols and aliphatic alcohols with various aryl as well as heteroaryl halides under ligand-free conditions are reported. This protocol provides a variety of diaryl ether and bis-diaryl ether motifs by reacting different aryl/aliphatic halides with differently substituted phenols and saturated alcohols in the presence of a catalytic amount of CuO on alumina and KOH as a base at moderate temperature under nitrogen atmosphere. The described methodology is simple, straightforward and efficient to afford the cross-coupled products in high yields under ligand-free conditions. The explored catalyst is inexpensive, air-stable and recyclable up to three cycles.
FLAME RETARDANT HALOGENATED PHENYL ETHERS
-
Page/Page column 12, (2011/08/08)
A halogenated non-polymeric phenyl ether is described having the general formula (I): wherein each X is independently Cl or Br, n is an integer of 1 or 2, each m is independently an integer of 1 to 5 and each p is independently an integer of 1 to 4, provided that, when X is Cl, the total amount halogen in the ether is from about 50 to about 65 wt% and when, X is Br, the total amount halogen in the ether is from at least 70 wt % to about 79 wt%.
Glyoxal bis(phenylhydrazone) as promoter for CuI-catalyzed O-arylation of phenols with bromoarenes
Liu, Yu-Hua,Li, Gang,Yang, Lian-Ming
experimental part, p. 343 - 346 (2009/04/19)
A very simple bishydrazone-type ligand, glyoxal bis(phenylhydrazone) (L1), was found to effectively promote the CuI-catalyzed O-arylation of phenols with aryl bromides. This cross-coupling reaction proceeded in acetonitrile at 60-80 °C in the presence of K3PO4 as base. A diverse array of phenols and bromoarenes was employed as substrates to afford diaryl ethers in good to excellent yields, and some base-sensitive groups, such as ester, aldehyde, and ketone groups, can survive under the mild reaction conditions.
Synthesis and structure of cyclic oligo(p-phenylene oxide)s, -(C 6H4O)n- (n = 6-10)
Takeuchi, Daisuke,Asano, Itaru,Osakada, Kohtaro
, p. 8614 - 8617 (2007/10/03)
Stepwise growth of oligo(p-phenylene oxide)s and cyclization via the Ullmann coupling reaction by using CuI/N,N-dimethylglycine afforded cyclic oligo(p-phenyleneoxide)s, -(C6H4O)n-(n = 6-10). The structure of the new cyclophanes was determined by X-ray crystallography, which revealed that they have planar or slightly bent structures with diameters of 1.0-1.5 nm.
N,N-Dimethyl Glycine-Promoted Ullmann Coupling Reaction of Phenols and Aryl Halides
Ma, Dawei,Cai, Qian
, p. 3799 - 3802 (2007/10/03)
(Matrix presented) Ullmann-type diaryl ether synthesis can be performed at 90°C using either aryl iodides or aryl bromides as the substrates under the assistance of N,N-dimethylglycine.
