- Nonsymmetrical Bis-Azine Biaryls from Chloroazines: A Strategy Using Phosphorus Ligand-Coupling
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Distinct approaches to synthesize bis-azine biaryls are in demand as these compounds have multiple applications in the chemical sciences and are challenging targets for metal-catalyzed cross-coupling reactions. Most approaches focus on developing new reagents as the formal nucleophilic coupling partner that can function in metal-catalyzed processes. We present an alternative approach using pyridine and diazine phosphines as nucleophilic partners and chloroazines where the heterobiaryl bond is formed via a tandem SNAr-phosphorus ligand-coupling sequence. The heteroaryl phosphines are prepared from chloroazines and are bench-stable solids. A range of bis-azine biaryls can be formed from abundant chloroazines using this strategy that would be challenging using traditional approaches. A one-pot cross-electrophile coupling of two chloroazines is feasible, and we also compared the phosphorus-mediated strategy with metal-catalyzed coupling reactions to show advantages and compatibility.
- Boyle, Benjamin T.,Hilton, Michael C.,McNally, Andrew
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supporting information
p. 15441 - 15449
(2019/11/02)
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- Synthesis, structure, and characterization of dinuclear copper(I) halide complexes with P^N ligands featuring exciting photoluminescence properties
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A series of highly luminescent dinuclear copper(I) complexes has been synthesized in good yields using a modular ligand system of easily accessible diphenylphosphinopyridine-type P^N ligands. Characterization of these complexes via X-ray crystallographic studies and elemental analysis revealed a dinuclear complex structure with a butterfly-shaped metal-halide core. The complexes feature emission covering the visible spectrum from blue to red together with high quantum yields up to 96%. Density functional theory calculations show that the HOMO consists mainly of orbitals of both the metal core and the bridging halides, while the LUMO resides dominantly on the heterocyclic part of the P^N ligands. Therefore, modification of the heterocyclic moiety of the bridging ligand allows for systematic tuning of the luminescence wavelength. By increasing the aromatic system of the N-heterocycle or through functionalization of the pyridyl moiety, complexes with emission maxima from 481 to 713 nm are obtained. For a representative compound, it is shown that the ambient-temperature emission can be assigned as a thermally activated delayed fluorescence, featuring an attractively short emission decay time of only 6.5 μs at φPL = 0.8. It is proposed to apply these compounds for singlet harvesting in OLEDs.
- Zink, Daniel M.,B?chle, Michael,Baumann, Thomas,Nieger, Martin,Kühn, Michael,Wang, Cong,Klopper, Wim,Monkowius, Uwe,Hofbeck, Thomas,Yersin, Hartmut,Br?se, Stefan
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p. 2292 - 2305
(2013/04/10)
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- Highly chemoselective metal-free reduction of phosphine oxides to phosphines
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Unprecedented chemoselective reductions of phosphine oxides to phosphines proceed smoothly in the presence of catalytic amounts of specific Br?nsted acids. By utilizing inexpensive silanes, e.g., PMHS or (EtO)2MeSiH, other reducible functional groups such as ketones, aldehydes, olefins, nitriles, and esters are well-tolerated under optimized conditions.
- Li, Yuehui,Lu, Liang-Qiu,Das, Shoubhik,Pisiewicz, Sabine,Junge, Kathrin,Beller, Matthias
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p. 18325 - 18329
(2013/01/15)
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- [NiCl2(dppp)]-catalyzed cross-coupling of aryl halides with dialkyl phosphite, diphenylphosphine oxide, and diphenylphosphine
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We present a general approach to C-P bond formation through the cross-coupling of aryl halides with a dialkyl phosphite, diphenylphosphine oxide, and diphenylphosphane by using [NiCl2(dppp)] as catalyst (dppp=1,3-bis(diphenylphosphino)propane). This catalyst system displays a broad applicability that is capable of catalyzing the cross-coupling of aryl bromides, particularly a range of unreactive aryl chlorides, with various types of phosphorus substrates, such as a dialkyl phosphite, diphenylphosphine oxide, and diphenylphosphane. Consequently, the synthesis of valuable phosphonates, phosphine oxides, and phosphanes can be achieved with one catalyst system. Moreover, the reaction proceeds not only at a much lower temperature (100-120 °C) relative to the classic Arbuzov reaction (ca. 160-220 °C), but also without the need of external reductants and supporting ligands. In addition, owing to the relatively mild reaction conditions, a range of labile groups, such as ether, ester, ketone, and cyano groups, are tolerated. Finally, a brief mechanistic study revealed that by using [NiCl2(dppp)] as a catalyst, the NiII center could be readily reduced in situ to Ni0 by the phosphorus substrates due to the influence of the dppp ligand, thereby facilitating the oxidative addition of aryl halides to a Ni0 center. This step is the key to bringing the reaction into the catalytic cycle. Making bonds: C-P bonds were formed by the Ni-catalyzed cross-coupling of aryl halides and phosphorus substrates without the need of external reductants. Aryl bromides and less reactive aryl chlorides underwent smooth coupling with several different phosphorus substrates to afford phosphonates, phosphine oxides, and phosphines (see scheme; dppp=1,3-bis(diphenylphosphino)propane). Due to the mild reaction conditions, a range of labile groups, such as ether, ester, ketone, and cyano groups, are tolerated. Copyright
- Zhao, Yu-Long,Wu, Guo-Jie,Li, You,Gao, Lian-Xun,Han, Fu-She
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supporting information; experimental part
p. 9622 - 9627
(2012/09/07)
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- General and selective copper-catalyzed reduction of tertiary and secondary phosphine oxides: Convenient synthesis of phosphines
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Novel catalytic reductions of tertiary and secondary phosphine oxides to phosphines have been developed. Using tetramethyldisiloxane (TMDS) as a mild reducing agent in the presence of copper complexes, PO bonds are selectively reduced in the presence of other reducible functional groups (FGs) such as ketones, esters, and olefins. Based on this transformation, an efficient one pot reduction/phosphination domino sequence allows for the synthesis of a variety of functionalized aromatic and aliphatic phosphines in good yields.
- Li, Yuehui,Das, Shoubhik,Zhou, Shaolin,Junge, Kathrin,Beller, Matthias
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supporting information; experimental part
p. 9727 - 9732
(2012/07/14)
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- A general bifunctional catalyst for the anti-Markovnikov hydration of terminal alkynes to aldehydes gives enzyme-like rate and selectivity enhancements
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A new, bifunctional catalyst for anti-Markovnikov hydration of terminal alkynes to aldehydes (6) allows practical room-temperature hydration of alkyl-substituted alkynes. Other outstanding features include near-quantitative aldehyde yields from both alkyl- and aryl-substituted alkynes and wide functional group tolerance. The uncatalyzed rate of alkyne hydration is measured for the first time, showing the enzyme-like rate and selectivity enhancements of aldehyde formation by 6. For aldehyde formation, an uncatalyzed rate -10 mol h-1 means a half-life >600 000, years. The catalyzed rate is up to 23.8 mol (mol 6)-1 h-1 and 10 000:1 ratio in favor of aldehyde. Changes in rate and selectivity induced by 6 are thus >2.4 × 1011 and 300 000, respectively. Copyright
- Grotjahn, Douglas B.,Lev, Daniel A.
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p. 12232 - 12233
(2007/10/03)
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- Alkoxycarbonylation of 3,3,3-Trifluoropropyne: An Intriguing Reaction to Prepare Trifluoromethyl-Substituted Unsaturated Acid Derivatives
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The addition of CO and methanol to 3,3,3-trifluoropropyne is catalysed by Pd(OAc)2 in the presence of (6-methylpyrid-2-yl)diphenylphosphine and CH3SO3H. The main products of the reaction are the methyl esters of 2-(trifluoromethyl)propenoic acid 1 and of 3-(trifluoromethyl)propenoic acid 2 (4,4,4-trifluorobut-2-enoic acid). The regioselectivity of the reaction can be controlled to a great extent by a suitable choice of the composition of the catalytic system and the reaction conditions. Thus, 1 can be obtained in 93% yield by using P(CO) = 20 atm and high ligand/Pd and acid/Pd ratios. On the other hand, selectivity up to 85% in 2 can be achieved using P(CO) = 80 atm and a low ligand/Pd ratio together with a high acid/Pd ratio. The reaction mechanism is also discussed.
- Scrivanti,Beghetto,Matteoli
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p. 543 - 547
(2007/10/03)
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- The chemistry of new nitrosyltungsten complexes with pyridyl- functionalized phosphane ligands
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The coordination chemistry of pyridylphosphanes, such as 2(6-tert- butylpyridyl)diphenylphosphane (Ph2P-tert-Bupy) (6) and 2-(6-tert- butylpyridyl)dimethylphosphane (Me2P-tert-Bupy) (7) towards a number of nitrosyltungsten complexes is reported. Displacement of the loosely coordinated MeCN from [W(CH3CN)3(CO)2(NO)][BF4] led to the following cationic compounds incorporating mono- and bidentate coordinated phosphane ligands: cis,cis-[W(CO)2(NO)(Ph2PR)(η2-Ph2PR)][BF4], [R = 2-pyridyl (9a), 2-picolyl (11)], cis,cis-[W(CO)(NO)(η2-Ph2Ppy)2][BF4] (20), trans,trans-[W(CO)(NO)(η2-Ph2Ppy)2][BPh4] (21), fac-[W(CO)2(NO) (Me2P- py)3][BF4] (16), fac-[W(CO)2(NO)(Me2P-tert-Bupy)3][BF4] (18), cis,cis- [W(CO)2(NO)(Me2Ppy)(η2-Me2Ppy)][BF4] (22), and cis,cis- [W(CO)2(CH3CN)(NO)(Me2P-tert-Bupy)2][BF4] (23a). The cationic complex cis,mer-[W(CO)3(NO)(Ph2P-tert-Bupy)2][PF6] (14) has been prepared by nitrosylation of cis/trans-W(CO)4(Ph2P-tert-Bupy)2 (13). Reactions of 9a, 11, 14, 16, and 18 with hydride transfer reagents afforded trans,- trans- HW(CO)2(NO)(Ph2Ppy)2 (10), trans, trans-HW(CO)2(NO)(Ph2Ppic)2 (12), trans, trans-HW(CO)2(NO)(Ph2-tBupy)2 (15), cis/trans- HW(CO)2(NO)(Me2Ppy)2 (17), and cis/trans-HW(CO)2(NO)(Me2P-tert-Bupy)2 (19), respectively. Reactivity experiments with acetic acid, hydroiodic acid, carbon dioxide, and acetylenedicarboxylic acid were performed, and were found to afford trans-W(CO)(NO)(Ph2Ppy)2(η2-CH3CO2) (24), trans, trans- IW(CO)2(NO)(Ph2Ppy)2 (25), trans-W(HCO2)(CO)2(NO)(Ph2Ppy)2 (26), and trans-W{η2-(Z)C(CO2Me)=CH[C(O)OMe]}(CO)(NO)(Ph2Ppic)2 (27), respectively. The influence of the pyridyl substituent in 10 was probed by a comparative H/D exchange experiment in which 10 and the analogous complex HW(CO)2(NO)(PPh3)2 were treated with MeOD. The deuterated complex trans,trans-WD(CO)2(NO)(Ph2Ppy)2 (28) could be isolated. The structures of 9a, 11, 14, and 20 have been determined by single-crystal X-ray diffraction analysis.
- Baur, Juergen,Jacobsen, Heiko,Burger, Peter,Artus, Georg,Berke, Heinz,Dahlenburg, Lutz
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p. 1411 - 1422
(2007/10/03)
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- Carbonylation catalyst system
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A catalyst system, which comprises: a) a source of a Group VIII metal; b) a phosphine having an aromatic substituent which contains an imino nitrogen atom; c) a source of protons; and d) a tertiary amine.
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