- Organocatalytic epoxidation and allylic oxidation of alkenes by molecular oxygen
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Pyrrole-proline diketopiperazine (DKP) acts as an efficient mediator for the reduction of dioxygen by Hantzsch ester under mild conditions to allow the aerobic metal-free epoxidation of electron-rich alkenes. Mechanistic crossovers are underlined, explaining the dual role of Hantzsch ester as a reductant/promoter of the DKP catalyst and a simultaneous competitor for the epoxidation of alkenes when HFIP is used as a solvent. Expansion of this protocol to the synthesis of allylic alcohols was achieved by adding a catalytic amount of selenium dioxide as an additive, revealing a superior method to the classical application of t-BuOOH as a selenium dioxide oxidant.
- Orfanidou, Maria,Petsi, Marina,Zografos, Alexandros L.
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supporting information
p. 9172 - 9178
(2021/11/30)
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- Catalytic Systems for Production of 1-Hexene by Selective Ethylene Trimerization
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Abstract: New chromium complexes with diphosphine ligands have been obtained by the reaction of chromium(III) hexahydrate and diphosphines in acetone. The structure of chromium(III) complex 4 containing water molecule and 1,2-bis(diphenylphosphino)benzene as ligands and that of two chromium(III) complexes (12 and 13) with 1,2-bis(diphenylphosphino)benzene ligands containing alkenyl substituents in the ortho-position of one of the phenyl groups at the phosphorous atom have been determined using X-ray diffraction analysis. The catalytic properties of the obtained complexes in the composition of catalytic systems for ethylene trimerization have been studied. It has been shown that the obtained series of catalytic systems manifests high activity in the process of ethylene trimerization to 1-hexene, with the process selectivity exceeding 94%. The highest value of productivity amongst known selective catalytic systems for trimerization was achieved using a chromium complex 13 bearing the 2-methylprop-1-enyl group at the ortho-position of one of the phenyl groups. The influence of temperature, pressure, the nature of the solvent and the composition of the catalytic system on the parameters of the process of ethylene trimerization to form 1-hexene has been determined.
- Afanas’ev, V. V.,Bespalova, N. B.,Cheredilin, D. N.,Kozlova, G. A.,Senin, A. A.,Sheloumov, A. M.
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- Quaternary Phosphorus-Induced Iodocuprate(I)-Based Hybrids: Water Stabilities, Tunable Luminescence and Photocurrent Responses
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Four (triphenyl)phosphonium-based quaternary phosphorus salts with different substituents (varying from methyl to n-butyl) were selected to be structural directed agents (SDAs) to construct four iodocuprate(I) hybrids via solution method, i.e., [(PPh3Me)(Cu3I4)]n (1), [(PPh3Et)(Cu3I4)]n (2), (PPh3iPr)2(Cu2I4) (3), [(PPh3nBu)(Cu3I4)]n (4). The inorganic iodocuprates in 1, 2 and 4 are 1-D (Cu3I4)nn– chains constructed from Cu5I11 units, but (Cu2I4)2– in 3 is a di-nuclear cluster. Interestingly, the strength of Cu···Cu and π–π stacking interactions are weakened with the lengthening of alkyl groups on P-atom. The best water stability of 4 can be ascribed to the better hydrophobicity of n-butyl group, which deters the dispersing of organic and inorganic moieties and as a result, inhibit hydrolysis reaction. Furthermore, all compounds exhibit typical reversible luminescent thermochromic behaviors, among which 4 exhibits blue emission and the quenching of higher energy (HE) zone in 1 and 2 are led by strong π–π stacking interactions. Besides, effective and repeatable photocurrent responses can be detected in these compounds. In all, by systematically introducing alkyl groups into (triphenyl)phosphonium as SDAs to prepare hybrid iodocuprates, we can find that the longer alkyl groups can achieve stronger tunable PL materials with enhanced water stabilities.
- Zhang, Wen-Ting,Liu, Jian-Zhi,Liu, Jing-Bo,Song, Kai-Yue,Li, Yi,Chen, Zhi-Rong,Li, Hao-Hong,Jiang, Rong
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supporting information
p. 4234 - 4244
(2018/10/15)
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- ATP3 and MTP3: Easily Prepared Stable Perruthenate Salts for Oxidation Applications in Synthesis
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The Ley–Griffith tetra-n-propylammonium perruthenate (TPAP) catalyst has been widely deployed by the synthesis community, mainly for the oxidation of alcohols to aldehydes and ketones, but also for a variety of other synthetic transformations (e.g. diol cleavage, isomerizations, imine formation and heterocyclic synthesis). Such popularity has been forged on broad reaction scope, functional group tolerance, mild conditions, and commercial catalyst supply. However, the mild instability of TPAP creates preparation, storage, and reaction reproducibility issues, due to unpreventable slow decomposition. In search of attributes conducive to catalyst longevity an extensive range of novel perruthenate salts were prepared. Subsequent evaluation unearthed a set of readily synthesized, bench stable, phosphonium perruthenates (ATP3 and MTP3) that mirror the reactivity of TPAP, but avoid storage decomposition issues.
- Moore, Peter W.,Read, Christopher D. G.,Bernhardt, Paul V.,Williams, Craig M.
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supporting information
p. 4556 - 4561
(2018/03/13)
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- Direct Cross-Coupling of Allylic C(sp3)?H Bonds with Aryl- and Vinylbromides by Combined Nickel and Visible-Light Catalysis
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An efficient protocol for the direct allylic C(sp3)?H bond activation of unactivated tri- and tetrasubstituted alkenes and their functionalization with aryl- and vinylbromides by nickel and visible-light photocatalysis has been developed. The method allows C(sp2)?C(sp3) formation under mild reaction conditions with good functional-group tolerance and excellent regioselectivity.
- Huang, Long,Rueping, Magnus
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supporting information
p. 10333 - 10337
(2018/07/31)
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- Photochromic performance of 1-thiazolyl-2-vinylcyclopentene derivatives having a phenyl-or 4-methoxyphenyl-substituted olefin
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1-Thiazolyl-2-vinylcyclopentene derivatives, 1-(5-methoxy-2-phenyl-4- thiazolyl)-2-(2-methyl-1-phenyl-1-propenyl) perfluorocyclopentene (1a), 1-[5-methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-2-(2-methyl-1-phenyl-1-propenyl) perfluorocyclopentene (2a), and 1-[5-methoxy-2-(4-methoxyphenyl)-4-thiazolyl]-2- [1-(4-methoxyphenyl)-2-methyl-1-propenyl] perfluorocyclopentene (3a) were synthesized in an attempt to obtain yellow photochromic compounds having low photocycloreversion quantum yields and large absorption coefficients of the closed-ring isomers. Their photochromic performance, thermal stability, and fatigue resistance were compared with 1-[5-methoxy-2-(4-methoxyphenyl)-4- thiazolyl]-2-(1,2-dimethyl-1-propenyl)perfluorocyclopentene (4a) having a methyl-substituted olefin. Upon irradiation with 313 nm light, compounds 1a, 2a, and 3a changed from colorless to various shades of yellow in toluene. The conversions from the open-ring (1a, 2a, and 3a) to the closed-ring (1b, 2b, and 3b) isomers in the photostationary state under irradiation with 313nm light were 93, 95, and 98%, respectively. Among the three derivatives 3b has the largest absorption coefficient (= 18900M-1cm-1) at 428nm and the lowest cycloreversion quantum yield of 1.8 10-3.
- Takami, Shizuka,Shimizu, Ayano,Shimizu, Kazuyuki,Miyoshi, Ryota,Yamaguchi, Tadatsugu,Irie, Masahiro
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p. 1059 - 1064
(2013/10/08)
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- Metal-catalyzed chemoselective cycloisomerization of cis-2,4-dien-1-als to 3-cyclopentenones and 4-alkylidene-3,4-dihydro-2H-pyrans
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PtCl2 (5 mol %) catalyst effected cycloisomerization of cis-2,4-dien-1-al (1) to 3-cyclopentenone (3) efficiently in hot toluene. In the presence of p-TSA, this PtCl2 catalysis gave 2-cyclopentenone (5) exclusively because of the secondary isomerization reaction. Although the 1-2 equilibrium state greatly favors aldehyde (1), PdCl2(PhCN) 2 (5 mol %) catalyzed cycloisomerization of aldehyde (1) to 4,6,7,8-tetrahydro-3H-isochromene (4) smoothly in hot toluene. A plausible mechanism is proposed on the basis of reaction observation and isotope-labeled experiment.
- Lo, Ching-Yu,Lin, Chung-Chang,Cheng, Hsin-Mei,Liu, Rai-Shung
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p. 3153 - 3156
(2007/10/03)
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- A Dynamic Equilibrium of Oxaphosphetanes
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The course of the Wittig reaction was investigated by rapid injection NMR spectroscopy.Rate constants for the formation of oxaphosphetanes were determined.A new dynamic equilibrium of oxaphosphetanes was observed for the first time.The solvent and substituent dependence of the new effect was investigated.By labeling various oxaphosphetanes with 13C and 17O the lithium salt dependence of the new equilibrium was shown.A lithium adduct of oxaphosphetanes under these conditions is proposed. - Key Words: Wittig reaction / Rapid injection NMR / Dynamic NMR / Oxaphosphetanes
- Geletneky, Christian,Foersterling, Frank-Holger,Bock, Willi,Berger, Stefan
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p. 2397 - 2402
(2007/10/02)
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- NEW EVIDENCE FOR AND NEW REACTIONS OF ORTHO-LITHIO YLIDS
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While α-lithio ylid 2 may be generated from triphenylphosphonio-bromomethylid through halogen/metal exchange, the reaction of triphenylphosphonio-methylid 1 with sec- or tert-butyllithium produces nearly quantitatively the o-lithio ylid 3, which is stable at -60 deg C but slowly decomposes at higher temperatures via a cyclization product 5 to give the α-lithio phosphine 4.
- Schaub, Bruno,Schlosser, Manfred
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p. 1623 - 1626
(2007/10/02)
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