排序方式: 共有14条查询结果,搜索用时 15 毫秒
1.
Bhaskar R. Aluri Mohammed Ghalib Markus K. Kindermann Peter G. Jones Joachim W. Heinicke 《Heteroatom Chemistry》2015,26(6):426-435
The reactivity of tBuLi (pentane) toward the N‐neopentyl‐substituted π‐excess P=CH–N heterocycle 1 depends on the solvent (tetrahydrofuran, diethyl ether, hexane, and toluene) and reaction conditions. Trapping of the resulting organolithium compounds with CO2/ClSiMe3, ClSiMe3, or EtI led to various products indicating CH lithiation ( 1a , b ), normal addition of tBuLi at the P=C bond (E/Z ‐2a , b ), inverse addition of the primary addition product 2Li at the P=C bond of a second molecule 1 , affording 3‐tert‐butyl‐2,2’‐bis(1,3‐benzazaphospholines) 3 , or inverse addition of tBuLi ( 4b,c ). The formation of 3 demonstrates a novel route to asymmetric heterocyclic 1,2‐diphosphine ligands. The structure elucidation of the new compounds is based on their 31P and 13C NMR data with conclusive chemical shifts and P–C coupling constants, that of the isolated PH‐functionalized diphosphine 3 on crystal structure analysis. 相似文献
2.
Anina Wöhl Dr. Wolfgang Müller Dr. Stephan Peitz Normen Peulecke Dr. Bhaskar R. Aluri Dr. Bernd H. Müller Dr. Detlef Heller Dr. Uwe Rosenthal Prof. Dr. Mohammed H. Al‐Hazmi Dr. Fuad M. Mosa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7833-7842
In this paper we report the results of an extensive experimental kinetic study carried out on the novel ethylene trimerization catalyst system, comprising the chromium source [CrCl3(thf)3] (thf=tetrahydrofuran), a Ph2P‐N(iPr)‐P(Ph)‐N(iPr)H (PNPNH) ligand (Ph=phenyl, iPr=isopropyl), and triethylaluminum (AlEt3) as activator. It could be shown that the initial activity shows a first‐order dependency on the ethylene concentration. Also, a first‐order dependency was found for the catalyst concentration. The initial activity follows a typical Arrhenius behavior with an experimentally determined activation energy of 52.6 kJ mol?1. At elevated temperatures (ca. 80 °C), a significant deactivation was observed, which can be tentatively traced back to a ligand rearrangement in the presence of AlEt3. After a fast initial phase, a pronounced ‘kink’ in the ethylene‐uptake curve is observed, followed by a slow, almost linear, further increase of the total ethylene consumption. The catalyst composition, in particular the ligand/chromium and the cocatalyst/chromium molar ratio, has a strong impact on the catalytic performance of the trimerization of ethylene. 相似文献
3.
Three new bicomponent hydrogels of riboflavin (R) with salicylic acid (S), dihydroxybenzoic acid (B) and acetoguanamine (D) in 1:1 molar ratio have been reported. FTIR and UV-vis spectra suggest formation of H-bonded complexes in 1:1 molar ratio of the components. The network consists of tape, bar and helical tubes for RB11, RS11 and RD11 systems, respectively. Reversible first order phase transition and invariant storage modulus (G') with angular frequency (ω) characterise the systems as forming thermoreversible hydrogels. The RD11 gel has the highest gel melting temperature and highest critical strain compared to other gels. WAXS study indicates different crystal structures for different gels. NMR spectra reveals higher shielding of protons in RD11 gel suggesting better π-stacking compared to RS11 and RB11 gels. RD11 gel shows two-fold enhancement of photoluminescence (PL) intensity with a substantial red shift of emission peak but RB11 and RS11 gels show PL-quenching. The gels exhibit a small decrease in lifetime and the PL property is very much temperature and pH dependent. So the complementary molecules have a pronounced effect on morphology, structure, stability and optical property of riboflavin gels. 相似文献
4.
Marc Gongoll Bernd H. Müller Stephan Peitz Bhaskar R. Aluri Normen Peulecke Anke Spannenberg 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):1845-1854
Abstract On the basis of the known aminodiphosphinoamine ligand Ph2PN(i-Pr)P(Ph) N(i-Pr)-H (3a), differently substituted aminodiphosphinoamine PNPN-H ligands (3) were prepared. By using different synthetic methods, the N-substituted ligands Ph2PN (i-Pr)P(Ph)N(c-Hex)-H (3b), Ph2PN(c-Hex)P(Ph)N(i-Pr)-H (3g), and Ph2PN(i-Pr)P(Ph) N[(CH2)3Si(OEt)3]-H (3c), in addition to the formerly described Ph2PN(n-Hex)P (Ph)N (i-Pr)-H (3h), Ph2PN(i-Pr)P(Ph)N(Et)-H (3d), Ph2PN(i-Pr)P(Ph)N(Me)-H (3e), and Ph2PN(c-Hex)P(Ph)N(c-Hex)-H (3f), were obtained. In addition, Ph2PN(i-Pr)P(Me)N(i-Pr)-H (3i), (cyclopentyl)2PN(i-Pr)P(Ph)N(i-Pr)-H (3j), (-O-CH2-CH2-O-)PN(i-Pr)P(Ph)N(i-Pr)-H (3k), and (1-Ad)2PN(i-Pr)P(Ph)N(i-Pr)-H (3l) were prepared with different P-substitutions. All compounds were characterized and the molecular structures of the intermediates Ph2PN(i-Pr)P(Ph)Cl (1a) and (cyclopentyl)2PN(i-Pr)P(Ph)Cl (1e) and the ligand (1-Ad)2PN(i-Pr)P(Ph)N(i-Pr)-H (3l) were investigated by single-crystal X-ray diffraction. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
5.
Aluri BR Kindermann MK Jones PG Heinicke J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(14):4328-4335
(1R)-1,3-Benzazaphospholes 1 a-c, P=CH-NR heterocycles of the indole type, react with tBuLi in two ways, depending on the steric demand of the N-substituent and the polarity of the medium. The presence of small N-alkyl groups induces CH-deprotonation in the 2-position to give hetaryllithium reagents 2 a and 2 b, whereas bulky N-substituents and nonpolar solvents change the reactivity towards addition at the P=C bond. The preferred regioselectivity is tert-butylation at phosphorus, occurring with excellent diastereoselectivity for trans-adducts 3 b and 3 c, but the inverse tert-butylation at C2 to 5 b was also observed. N-Neopentyl groups, with intermediate steric demand, give rise to formation of mixtures in ethers but allow switching either to selective CH lithiation in THF/KOtBu or to addition in pentane. Bulkier N-adamantyl groups always cause preferred addition. Protonation, silylation, and carboxylation were used to convert the P=CLi-NR, (E)-tBuP-CHLi-NR, and LiP-CH(tBu)-NR species into the corresponding sigma(2)-P or sigma(3)-P compounds 4 b and 6 a,b, 7 b,c, or 8 b-10 b with additional N and/or O donor sites. Slow diffusion-controlled air oxidation of 10 b led to the meso-diphosphine 11 b. Preferred eta(1)-P coordination was shown for an [Rh(cod)Cl] complex 12 b, and the potential of the new ligands 4 b and 7 b in catalysis was demonstrated by examples of Pd-catalyzed C-N coupling and Ni-catalyzed ethylene oligomerization (TON>6300). Crystal structures of 6 b, 11 b, and 12 b are presented. 相似文献
6.
We present here the first density functional theoretic study into the mechanism of cysteine dioxygenation by a model of cysteine dioxygenase enzymes. A large active site model containing the ligands bound to iron plus amino acid residues that are involved in hydrogen bonding interactions with the substrate is used. The reaction takes place via multi-state reactivity patterns on competing singlet, triplet, and quintet spin states, whereby the latter is the ground state in most complexes. Several new intermediates have been predicted, which have not been anticipated before. The dioxygen-bound complex is in a singlet spin ground state, and a state crossing to the quintet spin state leads to an FeOOS ring structure that splits into a cysteinyloxide radical that reorients and abstracts an electron from the iron center. In the final step, the oxoiron donates the oxygen atom to the substrate to produce cysteine sulfinic acid in a highly exothermic process. The rate-determining step is the initial step in the reaction mechanism on the quintet spin state surface. 相似文献
7.
8.
Stephan Peitz Bhaskar R. Aluri Dr. Normen Peulecke Dr. Bernd H. Müller Dr. Anina Wöhl Dr. Wolfgang Müller Dr. Mohammed H. Al‐Hazmi Dr. Fuad M. Mosa Uwe Rosenthal Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7670-7676
An alternative concept for the selective catalytic formation of 1‐octene from ethylene via dimeric catalytic centers is proposed. The selectivity of the tetramerization systems depends on the capability of ligands to form binuclear complexes that subsequently build up and couple two separate metallacyclopentanes to form 1‐octene selectively. Comparison of existing catalytic processes, the ability of the bis(diarylphosphino)amine (PNP) ligand to bridge two metal centers, and the experimental background support the proposed binuclear mechanism for ethylene tetramerization. 相似文献
9.
Aluri BR Niaz B Kindermann MK Jones PG Heinicke J 《Dalton transactions (Cambridge, England : 2003)》2011,40(1):211-224
A facile synthesis of functionally substituted 2-(hetero)aryl 1,3-benzazaphospholes via nickel- or palladium-catalyzed phosphonylation of N-acyl-2-bromoanilides 1a-k with triethyl phosphite is presented. Anilidophosphonates 2a-g with naphthoyl-, o-substituted phenyl, furoyl- or thenoyl groups allow direct reductive cyclization with LiAlH(4) to benzazaphospholes 3. The reaction of the o-bromoderivative 2d proceeds with concomitant replacement of bromine by hydrogen, whereas the electron-withdrawing pyridyl group of 2h prevents the synthesis of 3h by this short route. An alternative synthesis of 2-pyridylbenzazaphosphole 3hvia anilidophosphonates succeeded starting from Fmoc-anilinophosphonate 2kvia selective cleavage of the N-protecting group, reduction of the resulting phosphonoaniline to phosphinoaniline and cyclization with pyridine-2-carboxaldehyde via a dihydrobenzazaphosphole 8. N-Substituted pyridylmethylbenzazaphosphole 9 was detected as a side product. The structure elucidation of the new compounds is based on multinuclear NMR data and X-ray crystal structure analyses of a phosphonoanilide, underlining the dominance of N-H···O=P hydrogen bonds over N-H···O=C type hydrogen bonds, of 3h and a supramolecular associate of 3b and its unprecedented air oxidation product 10. 相似文献