- Synthesis and characterization of new PNNP-type chiral ligands
-
Polydentate ligands having both soft and hard centers are very effective ligands for the preparation of transition metal complexes. PNNP-type tetradentate diaminodiphosphine ligands are most preferred ligand types cause of their good efficiency for the asymmetric reactions. In this study, three different iminophosphine derivative PNNP-type chiral ligands were synthesized using (R)-(+)-1,1′-Binaphthyl-2,2′-diamine (R-BINAM) and d?phenylphosph?no benzaldehyde derivatives.
- Tezcan, Burcu,Güzel, Bilgehan
-
p. 315 - 316
(2018/12/11)
-
- Chemoselective Reduction of Sterically Demanding N,N-Diisopropylamides to Aldehydes
-
A sequential one-pot process for chemoselectively reducing sterically demanding N,N-diisopropylamides to aldehydes has been developed. In this reaction, amides are activated with EtOTf to form imidates, which are reduced with LiAlH(OR)3 [R = t-Bu, Et] to give aldehydes by hydrolysis of the resulting hemiaminals. The non-nucleophilic base 2,6-DTBMP remarkably improves reaction efficiency. The combination of EtOTf/2,6-DTBMP and LiAlH(O-t-Bu)3 was found to be optimal for reducing alkyl, alkenyl, alkynyl, and 2-monosubstituted aryl N,N-diisopropylamides. In contrast, EtOTf and LiAlH(OEt)3 in the absence of base were found to be optimal for reducing extremely sterically demanding 2,6-disubstituted N,N-diisopropylbenzamides. The reaction tolerates various reducible functional groups, including aldehyde and ketone. 1H NMR studies confirmed the formation of imidates stable in water. The synthetic usefulness of this methodology was demonstrated with N,N-diisopropylamide-directed ortho-metalation and C-H bond activation.
- Xiao, Peihong,Tang, Zhixing,Wang, Kai,Chen, Hua,Guo, Qianyou,Chu, Yang,Gao, Lu,Song, Zhenlei
-
p. 1687 - 1700
(2018/02/23)
-
- Ortho-Trialkylstannyl Arylphosphanes by C-P and C-Sn Bond Formation in Arynes
-
A novel and efficient approach to ortho-trialkylstannyl arylphosphanes by the reaction of arynes generated in situ with stannylated phosphanes (R3Sn-PR2) is described. Concurrent C-P and C-Sn bond formation occurs with high yields, and stannylated products are easily transformed into valuable ortho-substituted arylphosphanes. The reaction features high efficiency, good regioselectivity, and excellent practicality.
- Li, Yuanming,Chakrabarty, Shyamal,Mück-Lichtenfeld, Christian,Studer, Armido
-
p. 802 - 806
(2016/02/27)
-
- Dual encapsulation of electron transporting materials to simplify high-efficiency blue thermally activated delayed fluorescence devices
-
The charge flux balance and interfacial optimization are two core concerns when simplifying blue thermally activated delayed fluorescence (TADF) diodes, which reflects the more stringent demand on carrier transporting materials (CTM) as the embodiment of the contradiction between charge transportation and quenching suppression with the opposite requirement on intermolecular interactions. Herein, phenylbenzimidazole (PBI) was used as the core substituted with two diphenylphosphine oxide (DPPO) groups to form six dual-encapsulated charge-exciton separation (CES)-type electron transporting materials (ETM) with the collective name of xyPBIDPO. Through tuning the substitution positions of DPPO group, its two functions of resonance and steric effects were integrated and optimized to enhance charged moiety encapsulation without cost of reducing electroactivity. As the result, among xyPBIDPO, mmPBIDPO successfully realizes the balance of favorable electrical performance and interfacial interaction suppressions in virtue of its doubled mesa-substitution structure and roughly symmetrical configuration, rendering the good electron affinity of 2.8 eV, the high electron mobility by the level of 10-6 cm2 V-1 s-1 and effective PBI-core encapsulation. Consequently, mmPBIDPO was used to extremely simplify the blue TADF devices with the state-of-the-art performance from trilayer and quadruple-layer configurations, such as the maximum external quantum efficiency (EQE) beyond 20% and improved efficiency stability. This work not only established a solid example of CES-type ETM for high-performance simple structured blue TADF devices but also provided the direction of developing this kind of materials in the future.
- Kan, Wenjing,Duan, Chunbo,Sun, Mingzhi,Han, Chunmiao,Xu, Hui
-
p. 7145 - 7157
(2016/10/22)
-
- Ruthenium(II) complexes containing a phosphine-functionalized thiosemicarbazone ligand: Synthesis, structures and catalytic C-N bond formation reactions via N-alkylation
-
A series of ruthenium(II) complexes incorporating a thiosemicarbazone chelate tethered with a diphenylphosphine pendant have been studied. Thus, [(PNS-Et)RuCl(CO)(PPh3)] (1), [N,S-(PNS-Et)RuH(CO)(PPh3)2] (2) and [(PNS-Et)RuCl(PPh3)] (3) were synthesized by reactions of various RuII precursors with 2-(2-(diphenylphosphino)benzylidene)-N-ethylthiosemicarbazone (PNS-Et). However, complexation of PNS-Et with an equimolar amount of [RuCl2(dmso)4] resulted in two different entities [(PNS-Et)RuCl(dmso)2] (4) and [(PNS-Et)2Ru] (5) with different structural features in a single reaction. All the RuII complexes have been characterized by analytical and various spectroscopic techniques. Compounds 1-5 were recrystallized, and the X-ray crystal structures have been reported for 1, 2 and 5. In the complexes 1 and 3-5 the ligand coordinated in a tridentate monobasic fashion by forming PNS five- and six-membered rings, whereas in 2, the ligand coordinated in a bidentate monobasic fashion by forming a strained NS four-membered ring. Furthermore, compounds 1-5 showed catalytic activity in N-alkylation of heteroaromatic amines. Notably, complexes 1-3 were found to be very efficient catalysts toward N-alkylation of a wide range of heterocyclic amines with alcohols. In the presence of a catalytic amount of 2 with 50 mol% of KOH, N1,C5-dialkylation of 4-phenylthiazol-2-amine has been investigated. Reaction of in situ generated aldehyde with amine yields the N1,C5-dialkylated products through the hydride ion transformation from alcohol. Complexes 1-3 also catalyzed a variety of coupling reactions of benzyl alcohols and sulfonamides, which were realized often with 99% isolated yields. Advantageously, only one equivalent of the primary alcohol was consumed in the process.
- Ramachandran, Rangasamy,Prakash, Govindan,Selvamurugan, Sellappan,Viswanathamurthi, Periasamy,Malecki, Jan Grzegorz,Linert, Wolfgang,Gusev, Alexey
-
p. 11405 - 11422
(2015/03/05)
-
- Dynamic Covalent Organocatalysts Discovered from Catalytic Systems through Rapid Deconvolution Screening
-
The first example of a bifunctional organocatalyst assembled through dynamic covalent chemistry (DCC) is described. The catalyst is based on reversible imine chemistry and can catalyze the Morita-Baylis-Hillman (MBH) reaction of enones with aldehydes or N-tosyl imines. Furthermore, these dynamic catalysts were shown to be optimizable through a systemic screening approach, in which large mixtures of catalyst structures were generated, and the optimal catalyst could be directly identified by using dynamic deconvolution. This strategy allowed one-pot synthesis and in situ evaluation of several potential catalysts without the need to separate, characterize, and purify each individual structure. The systems were furthermore shown to catalyze and re-equilibrate their own formation through a previously unknown thiourea-catalyzed transimination process.
- Schaufelberger, Fredrik,Ramstr?m, Olof
-
supporting information
p. 12735 - 12740
(2015/09/01)
-
- A practical in situ generation of the schwartz reagent. reduction of tertiary amides to aldehydes and hydrozirconation
-
A new, highly efficient in situ protocol (Cp2ZrCl2/LiAlH(OBu-t)3) is described for the generation of the Schwartz reagent which provides a convenient method for the amide to aldehyde reduction and the regioselective hydrozirconation-iodination of alkynes and alkenes. Highlighted are chemoselective reductions of benzamides derived by directed ortho metalation (DoM) chemistry, allowing the synthesis of valuable 1,2,3-substituted benzaldehydes. The single-step, three-component process proceeds in a very short reaction time, shows excellent functional group compatibility, and uses inexpensive and long-storage stable reducing reagents.
- Zhao, Yigang,Snieckus, Victor
-
supporting information
p. 390 - 393
(2014/04/03)
-
- A remarkable cis- and trans-spanning dibenzylidene acetone diphosphine chelating ligand (dbaphos)
-
A multidentate and flexible diolefin-diphosphine ligand, based on the dibenzylidene acetone core, namely dbaphos (1), is reported herein. The ligand adopts an array of different geometries at Pt, Pd and Rh. At PtII the dbaphos ligand forms cis- and trans-diphosphine complexes and can be defined as a wide-angle spanning ligand. 1H NMR spectroscopic analysis shows that the β-hydrogen of one olefin moiety interacts with the PtII centre (an anagostic interaction), which is supported by DFT calculations. At Pd0 and RhI, the dbaphos ligand exhibits both olefin and phosphine interactions with the metal centres. The Pd0 complex of dbaphos is dinuclear, with bridging diphosphines. The complex exhibits the coordination of one olefin moiety, which is in dynamic exchange (intramolecular) with the other "free" olefin. The Pd0 complex of dbaphos reacts with iodobenzene to afford trans-[PdII(dbaphos)I(Ph)]. In the case of RhI, dbaphos coordinates to form a structure in which the phosphine and olefin moieties occupy both axial and equatorial sites, which stands in contrast to a related bidentate olefin, phosphine ligand ("Lei" ligand), in which the olefins occupy the equatorial sites and phosphines the axial sites, exclusively. Copyright
- Jarvis, Amanda G.,Sehnal, Petr E.,Bajwa, Somia E.,Whitwood, Adrian C.,Zhang, Xiangbiao,Cheung, Man Sing,Lin, Zhenyang,Fairlamb, Ian J. S.
-
p. 6034 - 6043
(2013/06/27)
-
- CuI complexes containing a multidentate and conformationally flexible dibenzylidene acetone ligand (dbathiophos): Application in catalytic alkene cyclopropanation
-
The synthesis and characterisation of a multidentate conformationally flexible ligand based on the dibenzylidene acetone core structure, dbathiophos (1), is described. Ligand 1 has a high affinity for cationic and neutral Cu I species. Three unique CuI complexes (4-6) are reported showing that the ligand backbone of dbathiophos is hemilabile, and able to adopt different 1,4-dien-3-one conformational geometries around CuI. Complexes 4 and 6 both effectively catalyse the cyclopropanation of styrene with ethyl diazoacetate at low catalyst loadings (1 mol% Cu). The Royal Society of Chemistry 2011.
- Jarvis, Amanda G.,Whitwood, Adrian C.,Fairlamb, Ian J. S.
-
p. 3695 - 3702
(2011/07/30)
-
- Arene-ruthenium(II) complexes containing amino-phosphine ligands as catalysts for nitrile hydration reactions
-
Three different series of novel mononuclear arene-ruthenium(II) complexes containing amino-phosphine ligands, namely, [RuCl2{κ 1(P)-2-Ph2PC6H4CH 2NHR}(η6-arene)], [RuCl2{κ 1(P)-3-Ph2PC6H4CH 2NHR}(η6-arene)], and [RuCl2{κ 1(P)-4-Ph2PC6H4CH 2NHR}(η6-arene)] (arene = C6H6, p-cymene, 1,3,5-C6H3Me3, C6Me 6; R = iPr, tBu; all combinations), have been synthesized and fully characterized. These readily accessible species are efficient catalysts for the selective hydration of organonitriles into amides under challenging reaction conditions, i.e., pure aqueous medium in the absence of any cocatalyst, being much more active than their corresponding nonfunctionalized triphenylphosphine counterparts [RuCl2(PPh 3)(η6-arene)]. The results obtained in this study indicate that the (amino-phosphine)ruthenium(II) complexes operate through a "bifunctional catalysis" mechanism in which the ruthenium center acts as a Lewis acid, activating the nitrile molecule, and the P-donor ligand acts as a Brnsted base, the pendant amino group generating the real nucleophile of the hydration process, i.e., the OH- group.
- Garcia-Alvarez, Rocio,Diez, Josefina,Crochet, Pascale,Cadierno, Victorio
-
scheme or table
p. 3955 - 3965
(2010/12/25)
-
- Schwartz Reagents: Methods of In Situ Generation and Use
-
Embodiments of the invention provide a method of using Schwartz Reagent, Cp2Zr(H)Cl, without accumulating or isolating it. Methods provide mixtures of Cp2ZrCl2, reductants that selectively reduce Cp2ZrCl2, and substrates. After reaction of Cp2ZrCl2 and the reductant, an intermediate reduction product is formed, apparently Schwartz Reagent. The in situ Schwartz Reagent then selectively reduces certain functional groups on the substrate. Substrates include tertiary amides, tertiary benzamides, aryl O-carbamates, and heteroaryl N-carbamates, which are reduced to aldehydes, benzaldehydes, aromatic alcohols, and heteroaromatics, respectively. Compared to prior methods, reagents are inexpensive and stable, reaction times are short, and reaction temperature in certain cases is conveniently room temperature. It has been estimated that using the in situ method described herein instead of synthesized or commercially obtained Schwartz Reagent provides a 50% reduction in cost.
- -
-
Page/Page column 7; 13
(2010/06/19)
-
- Superior effect of a π-acceptor ligand (phosphine-electron-deficient olefin ligand) in the Negishi coupling involving alkylzinc reagents
-
(Chemical Equation Presented) Palladium-catalyzed Negishi cross-coupling involving primary and secondary alkyls, even in the presence of β-H, can be achieved at ambient temperature using chelating ligands containing a phosphine and an electron-deficient olefin. The superior effects of the ligands were shown not only in the desired cross-coupling product yields but also in the fast reaction at mild conditions. This reaction has been also scaled up to 50 g in 0.005 mol % catalyst (20,000 TONs) at room temperature.
- Luo, Xiancai,Zhang, Heng,Duan, Hui,Liu, Qiang,Zhu, Lizheng,Zhang, Tony,Lei, Aiwen
-
p. 4571 - 4574
(2008/03/12)
-
- Modular multidentate phosphine ligands: Application to palladium-catalyzed allylic alkylations
-
Multidentate phosphines were readily obtained by reaction of chiral multidentate amines, prepared via ring opening of (S)-N-tosyl-2- isopropylaziridine with ammonia, primary, and secondary amines, with achiral phosphorus containing building blocks. The phosphines were used in palladium-catalyzed alkylation of rac-3-cyclohexenyl and cyclopentenyl carbonates. The enantioselectivity and reactivity were largely dependent on the structure of the amine core of the ligands. Up to 88% ee was observed in reactions with the six-membered substrate. The Royal Society of Chemistry 2006.
- Pei, Yuxin,Brule, Emilie,Moberg, Christina
-
p. 544 - 550
(2008/02/02)
-
- o-diphenylphosphinobenzaldehyde complexes of palladium(II) and platinum(II): Synthesis, spectroscopy and structure
-
Preparation of the o-diphenylphosphinobenzaldehyde complexes of Pd(II) and Pt(II), with general formulae [MX2L2], [Pd 2Me2(μ-Cl)2L2] and [PdMeClL 2] where [M = Pd or Pt; X = Cl, Br, I and L = o- diphenylphosphinobenzaldehyde, {PPh2(o-C6H 4CHO)}], is reported here. All complexes have been characterized by elemental analysis, IR, NMR (1H, 13C, 31P and 195Pt) and UV-visible spectroscopy, that allowed the deduction of the stereochemistry for the complexes. The mononuclear complexes have been found to adopt the trans configuration in square-planar geometries. The molecular structure of trans-[PdCl2{PPh2(C6H 4CHO)}2] has been established by a single crystal X-ray diffraction study and confirms the spectroscopic conclusions.
- Mahalakshmi,Phadnis, Prasad P.,Jain, Vimal K.,Tiekink, Edward R. T.
-
p. 2287 - 2293
(2007/10/03)
-
- Use of molecular weight-enlarged catalysts in a process for asymmetric, continous hydrogenation, novel molecular weight-enlarged ligands and catalysts
-
The first embodiment of the present invention provides a process, which includes: in a continuous process in a membrane reactor, asymmetrically hydrogenating at least one C=C, C=N or C=O double bond with a catalyst. Another embodiment of the present invention provides a ligand, which includes at least one di-1,3-aminophosphine homochiral active center; optionally, a linker; and a molecular weight-enlarging polymer; wherein the active center is bound to the molecular weight-enlarging polymer through the linker or is bound directly to the molecular weight-enlarging polymer; and wherein the linker is defined in the claims. Another embodiment of the present invention provides a process for preparing the above-noted ligand, and a catalyst that includes the above-noted ligand.
- -
-
-
- Continuous Application of Chemzymes in a Membrane Reactor: Asymmetric Transfer Hydrogenation of Acetophenone
-
The application of homogeneously soluble catalysts is limited by the recovery in cases where the price of the catalyst is high. Biological catalysts, enzymes, can be efficiently recycled by means of an ultrafiltration membrane due to their high molecular weight, for example, in the continuously operated membrane reactor. In order to transfer this principle to chemical catalysis, we have attached a transfer hydrogenation catalyst, first invented by Gao and Noyori, to a polymer. The resulting homogeneously soluble, polymer-bound catalyst (chemzyme) can now be retained by ultrafiltration membranes like enzymes. On applying this catalyst in continuously operated membrane reactors, a continuous isopropoxide dosage is necessary in order to compensate deactivation caused by water residues in the feed stream. Thus, high space-time yields up to 578 g L-1 d-1 and enantioselectivities up to 94% can he achieved. These results were compared to an enzyme catalyzed system consisting of a carbonyl reductase that also utilizes 2-propanol as a hydrogen source for the cofactor regeneration of NADH.
- Laue, Stephan,Greiner, Lasse,W?ltinger, Jens,Liese, Andreas
-
p. 711 - 720
(2007/10/03)
-
- Water Soluble Phosphanes, XIV [1]. Hydrophilic Derivatives of Triphenylphosphane with NH2, COOH and P(O)(OR)2 Functionalized Side Chains
-
Nucleophilic phosphanylation of ortho-fluorophenylacetic acid or ortho-fluorobenzylamine with PhPH2 using KOtBu as the base affords the hydrophilic tertiary phosphanes 3 and 4a with terminal CH2-COOH and CH2-NH2 substituents. The corresponding secondary phosphane ligands 2 or 5 may be obtained by Pd-catalyzed P-C coupling of ortho-iodophenylacetic acid with PhPH2 or selective nucleophilic phosphanylation of ortho-fluorophenylacetic acid. Novel phosphonatomethyl derivatives 7a, 7b of triphenylphosphane have been obtained in a two stage synthesis using ortho-iodobenzylchloride or meta-iodobenzylbromide as starting materials. Arbusov reaction with P(OEt)3 and Pd-catalyzed P-C coupling reactions with Ph2PH gave the esters 7a, 7b. Purification of 7a was achieved via its BH3 adduct 8a. Deprotection, hydrolysis and neutralisation with NaOH affords the water soluble sodium salts 9a,9b. α-Hydroxy and α-benzylamino derivatives 12 and 14 of ortho-diphenylphosphanobenzyl phosphonate (e.g. 7a) and the corresponding Me2P(O) analogs 13 and 16 are accessible in a straightforward manner by addition of (MeO)2P(O)H or Me2P(O)H to ortho-phosphanobenzaldehyde 11a or its benzaldimino derivative 15, respectively. An improved synthesis for 11a-11c has been developed. Reaction of 11a with the Wittig reagent Ph3P=C(H)COOEt and subsequent hydrolysis of the intermediate ester 17a affords ortho-diphenylphosphano cinnamic acid 17. The catalytical activity of 1, 9a, 9b and related ligands in Suzuki-type coupling reactions has been investigated.
- Liek, Christian,Machnitzki, Peter,Nickel, Thomas,Schenk, Stefan,Tepper, Michael,Stelzer, Othmar
-
p. 1532 - 1542
(2007/10/03)
-
- A novel convenient synthesis of aryl phosphines containing reactive functional groups
-
A convenient method is described for the preparation of Ph2PC6H4COOH-2 (2) and Ph2PC6H4CHO-2 (5).
- Ravindar,Hemling,Schumann,Blum
-
p. 1453 - 1459
(2007/10/02)
-