4039-32-1Relevant articles and documents
Synthesis of the carbon framework of scholarisine a by intramolecular oxidative coupling
Watanabe, Tsugunori,Kato, Nobuki,Umezawa, Naoki,Higuchi, Tsunehiko
, p. 4255 - 4261 (2013)
Scholarisine A, isolated from the leaves of Alstonia scholaris, is a monoterpene indole alkaloid with an unprecedented cage-like structure. In this paper, preparation of the distinctive cage-like core skeleton of scholarisine A is described. The key feature of this synthetic strategy is an intramolecular oxidative coupling reaction at the late stage to construct a 10-oxa-tricyclo[5.3.1.03, 8]undecan-9-one structure fused with indolenine. Intramolecular oxidative coupling by using N-iodosuccinimide gave the carbon framework of scholarisine A in moderate yield, which is the first example of intramolecular oxidative-coupling reaction between non-activated enolate and indole. This study lays the foundation for continued investigations towards the total synthesis of scholarisine A. Copyright
The synthesis of pentadienylium salts via reactions of (5-ethoxy-1,5-diaryl-2,4-pentadienylidene)ethyloxonium perchlorate with hydrazines
Riviere, Francois,Romanenko, Vadim D.,Mazieres, Marie-Rose,Sanchez, Michel,Wolf, Jean-Gerard
, p. 6717 - 6720 (1996)
Reaction of the readily available (5-ethoxy-1,5-diaryl-2,4-pentadienylidene)ethyloxonium perchlorate 1 with hydrazines, R2NNH2 or RNHNH2, provides a simple and efficient synthesis of previously unknown (5-ethoxy-1,5-diaryl-2,4-pentadienylidene)hydrazinium salts 2a-d. Application of this method to the synthesis of the highly conjugated pentadienylium salt from terephthalic dihydrazide is reported.
Synthesis and grafting of CAN-derived tetravalent cerium alkoxide silylamide precursors onto mesoporous silica MCM-41
Crozier, Alan R.,Schaedle, Christoph,Maichle-Moessmer, Caecilia,Toernroos, Karl W.,Anwander, Reiner
, p. 5491 - 5499 (2013)
The heteroleptic tetravalent cerium complex [Ce(OiPr) 3{N(SiMe3)2}]2 was synthesised by treating ceric ammonium nitrate (CAN) sequentially with sodium isopropoxide and lithium bis(trimethylsilyl)amide in THF. The trivalent ate complex [Ce(OiPr)2{N(SiMe3)2]2}][Li(thf) 2] was also isolated from these reaction mixtures. A transsilylamination reaction of [Ce(OiPr)3{N(SiMe3) 2}]2 with tetramethyldisilazane produced a considerable amount of homoleptic Ce[N(SiHMe2)2]4. The polymeric complex [Li2Ce2(OiPr)10(1,4-dioxane)] n was isolated as an additional ligand redistribution product. When tetravalent complexes Ce[N(SiHMe2)2]4, Ce[N(SiMe3)2]3Cl and Cp3CeCl were allowed to react with samples of periodic mesoporous silica MCM-41, Ce(iv) hybrid materials were produced. All hybrid materials were characterised via N2 physisorption, elemental analysis and DRIFT spectroscopy.
Synthesis and structural elucidation of solvent-free and solvated lithium dimethyl (HMDS) zincates
Armstrong, David R.,Herd, Emma,Graham, David V.,Hevia, Eva,Kennedy, Alan R.,Clegg, William,Russo, Luca
, p. 1323 - 1330 (2008)
Using a co-complexation methodology the unsolvated lithium zincate [LiZn(HMDS)Me2] (4, HMDS = 1,1,1,3,3,3-hexamethyldisilazide) was prepared by reaction of an equimolar amount of LiHMDS with Me2Zn in a non-polar toluene-hexane solvent mixture. X-Ray crystallographic studies reveal that the asymmetric unit of 4 has a dinuclear arrangement, based on a planar LiNZnC four-membered ring. As a result of intermolecular interactions between the lithium centre of one asymmetric unit and a terminal methyl group of another, 4 presents a polymeric chain array in the solid state. DFT calculations revealed that the formation of the polymer is the driving force for the success of co-complexation of LiHMDS and Me2Zn to yield the unsolvated zincate 4. The reaction of 4 with PMDETA (N,N,N′,N″,N″- pentamethyldiethylenetriamine) afforded the new solvated zincate [(PMDETA)Li(μ-Me)Zn(HMDS)Me] (5). X-Ray crystallographic studies show that the asymmetric unit of 5 consists of an open, dinuclear LiCZnC arrangement rather than a closed cyclic one, in which the HMDS ligand unusually occupies a terminal position on Zn. DFT computational studies showed that the structure found for 5 was energetically preferred to the expected HMDS-bridging isomer due to the steric hindrance imposed by the tridentate PMDETA ligand. The reaction of 4 with the neutral nitrogen donors 4-tert-butylpyridine and tert-butylcyanide afforded the homometallic compounds [(tBu-pyr)Li(HMDS)] (6) and [(tBuCN)Li(HMDS)] (7) respectively as a result of disproportionation reactions. Compounds 6 and 7 were characterized by NMR (1H, 13C and 7Li) spectroscopy. The Royal Society of Chemistry.
A trigonal-pyramidal Erbium(III) single-molecule magnet
Brown, Andrew J.,Pinkowicz, Dawid,Saber, Mohamed R.,Dunbar, Kim R.
, p. 5864 - 5868 (2015)
Given the recent advent of mononuclear single-molecule magnets (SMMs), a rational approach based on lanthanides with axially elongated f-electron charge cloud (prolate) has only recently received attention. We report herein a new SMM, [Li(THF)4[Er{N(SiMe3)2}3Cl] 2 THF, which exhibits slow relaxation of the magnetization under zero dc field with an effective barrier to the reversal of magnetization (ΔEeff/kB=63.3 K) and magnetic hysteresis up to 3 K at a magnetic field sweep rate of 34.6 Oe s-1. This work questions the theory that oblate or prolate lanthanides must be stabilized with the appropriate ligand framework in order for SMM behavior to be favored.
An Efficient Directed Claisen Reaction Allows for Rapid Construction of 5,6-Disubstituted 1,3-Dioxin-4-ones
Zhang, Ziyang,Kitamura, Yoshiaki,Myers, Andrew G.
, p. 2709 - 2712 (2015)
An efficient directed Claisen reaction between tert-butyl propionate and phenyl propionate is described. This enables a practical synthesis of 6-ethyl-2,2,5-trimethyl-4H-1,3-dioxin-4-one and thereby (Z)-[(4-ethylidene-2,2,5-trimethyl-4H-1,3-dioxin-6-yl)oxy]trimethylsilane, a key building block in our synthesis of macrolide antibiotics. The three-step route elaborated for the preparation of the latter substance requires no chromatography and is amenable to large-scale synthesis.
NMR spectroscopic study of the adduct formation and reactivity of homoleptic rare earth amides with alkali metal benzyl compounds, and the crystal structures of [Li(TMEDA)2][Nd{N(SiMe3)2}3(CH2Ph)] and [{Li(TMP)}2{Li(Ph)}]2
Rachor, Simon G.,Cleaves, Peter A.,Robertson, Stuart D.,Mansell, Stephen M.
, p. 101 - 109 (2018)
An NMR spectroscopic study has been conducted into the reactivity of alkali metal benzyls [M(CH2Ph)], (M = Li, Na, K) with lanthanide tris(amide) complexes [Ln(N″)3] (Ln = Y, Ce, Nd; N″ = N(SiMe3)2) and [Ce(TMP)3] (TMP = 2,2,6,6-tetramethylpiperidide). It was found that for [Ln(N″)3], benzyl adducts [M][Ln(N″)3(CH2Ph)] were initially formed, and the molecular structure for M = Li(TMEDA)2 and Ln = Nd was determined revealing a distorted tetrahedral [Nd(N″)3(CH2Ph)] anion. In all cases, these adduct complexes were unstable, intramolecularly deprotonating a methyl arm of a N″ ligand via benzyl basicity and eliminating toluene to prepare cyclometallated complexes of the form [M][Ln(N″)2{κ2-CH2Si(Me)2N(SiMe3)}]. In parallel studies, reactions of [Li(Ph)] with [Ln(N″)3] (Ln = Ce, Nd) afforded [Li(N″)], whilst for (Ln = Y) adduct formation was observed. [Ce(TMP)3] did not generate any characterisable bimetallic adducts. The reaction of [Li(Ph)] with [Li(TMP)] afforded the hexanuclear [{Li(TMP)}2{Li(μ-Ph)}]2, which features lithium in three different coordination environments.
TITRATION OF ORGANIC COMPOUNDS AS VERY WEAK ACIDS WITH LITHIUM SILANAMIDE
Clyde, Dale D.
, p. 1308 - 1310 (1980)
Numerous organic compounds, such as alcohols, acetophenones, esters, anilides, carbamates, and lactams, can be titrated as very weak acids in tetrahydrofuran.End points were determined by potentiometry and by color change of N-phenyl-p-aminoazobenzene.Relative percent errors for the determination of approximately 1.00-mmol amounts of sample generally ranged from 2 to 6percent.Examples of compounds which did not react quantitatively with the lithium silylamide reagent were benzophenone, benzylbenzoate, and N-phenylbenzylamine.
Accessing Photoredox Transformations with an Iron(III) Photosensitizer and Green Light
Aydogan, Akin,Bangle, Rachel E.,Cadranel, Alejandro,Turlington, Michael D.,Conroy, Daniel T.,Cau?t, Emilie,Singleton, Michael L.,Meyer, Gerald J.,Sampaio, Renato N.,Elias, Benjamin,Troian-Gautier, Ludovic
supporting information, p. 15661 - 15673 (2021/10/01)
Efficient excited-state electron transfer between an iron(III) photosensitizer and organic electron donors was realized with green light irradiation. This advance was enabled by the use of the previously reported iron photosensitizer, [Fe(phtmeimb)2]+ (phtmeimb = {phenyl[tris(3-methyl-imidazolin-2-ylidene)]borate}, that exhibited long-lived and luminescent ligand-to-metal charge-transfer (LMCT) excited states. A benchmark dehalogenation reaction was investigated with yields that exceed 90% and an enhanced stability relative to the prototypical photosensitizer [Ru(bpy)3]2+. The initial catalytic step is electron transfer from an amine to the photoexcited iron sensitizer, which is shown to occur with a large cage-escape yield. For LMCT excited states, this reductive electron transfer is vectorial and may be a general advantage of Fe(III) photosensitizers. In-depth time-resolved spectroscopic methods, including transient absorption characterization from the ultraviolet to the infrared regions, provided a quantitative description of the catalytic mechanism with associated rate constants and yields.
Designing Stability into Thermally Reactive Plumbylenes
Ba?i?, Goran,Zanders, David,Mallick, Bert,Devi, Anjana,Barry, Seán T.
, p. 8218 - 8226 (2018/07/25)
Lead analogues of N-heterocyclic carbenes (NHPbs) are the least understood members of this increasingly important class of compounds. Here we report the design, preparation, isolation, structure, volatility, and decomposition pathways of a novel aliphatic NHPb: rac-N 2,N 3-di-tert-butylbutane-2,3-diamido lead(II) (1Pb). The large steric bulk of the tert-butylamido moieties and rac-butane backbone successfully hinder redox decomposition pathways observed for diamidoethylene and -ethane backbone analogues, pushing the onset of thermal decomposition from below 0 °C to above 150 °C. With an exceptionally high vapor pressure of 1 Torr at 94 ± 2 °C and excellent thermal stability among Pb(II) complexes, 1Pb is a promising precursor for the chemical vapor deposition (CVD) and atomic layer deposition (ALD) of functional lead-containing materials.
