762-99-2Relevant academic research and scientific papers
ν-alkoxy-β-ketoiminate complexes of groups 4 and 5: Synthesis and characterization of the complexes [(η-C5H4R)M{CH3C(O)CHC(NCH 2CHR'O)CH3}Cln] (M = Ti, n = 1; M = Nb, n = 2; R = H, Me; R′ = H, Me), [Ti{CH3C(O)CHC(NCH2CHR'O)CH3}Cl 2(thf)]
Doherty, Simon
, p. 1018 - 1029 (1999)
The synthesis and characterization of a range of ν-alkoxo β-ketoiminate complexes of groups 4 and 5 are reported. Reactions between the acylic ν-hydroxyalkyl β-ketoimines CH3C(O)CII2C(NCH2CHR'OH)CH3 (R′ = H, Me) and [(η2-C5H4R)TiCl3] (R = H, Me) in the presence of triethylamine afford the monocyclopentadienyl derivatives [(η-C5H4R)Ti-{CH3C(O)CHC(NCH 2CHR'O)CH3}C1] (R = H, R′ = H, 2a; R = Me, R′ = H, 2b; R = H, R′ = Me, 2c; R = Me, R′ = Me, 2d). Complex 2a adopts a square pyramidal coordination geometry with the Cp occupying the apical site and the terdentate ketoiminate and chloride occupying basal positions. Upon standing in thf, solutions of 2a-d containing NEt3HCl deposit deep orange crystals of [Ti{CH3C(O)CHC(NCH2CHR'O)CH3}Cl2(thf)] (R′ = H, 3a; R′ = Me, 3b) via protonolysis of the Ti-Cp bond. Alternatively, compounds 3a and 3b can be prepared in near quantitative yield either from the reaction between [TiCl4(thf)2] and the corresponding acylic ν-hydroxyalkyl β-ketoimine, in the presence of NEt3, or via a ligand exchange reaction between [Ti(OPri)2Cl2] and the ν-hydroxyalkyl β-ketoimine. Variable-temperature 2H NMR studies of 3a and 3b have shown that stereoisomers of these complexes interchange via a dissociative dynamic process, involving the trigonal bypyramidal intermediate [Ti-{CH3C(O)CHC(NCH2CHR′O)CH3}Cl 2]. The free energy of activation associated with this exchange has been determined (ΔG = 45.5 kJ mol-1, 3a; ΔG = 47.0 kJ mol-1, 3b). Surprisingly, treatment of [TiCOPri4] with ν-hydroxyalkyl β-ketoimine (1:1) results in complete alcoholysis to afford [Ti{CH3C(O)CHC(NCH2CHR'O)CH3}2] (R′ = H, 4a; R′ = Me, 4b), which contain two meridianally coordinated terdentate ketoiminate ligands. The reactions between ν-hydroxyalkyl β-ketoimine derivatives and [(η2-C5H4R)NbCl4] afford [(η2C5H4R)Nb{CH3C(O)CHC(NCH 2CHR'O)CH3}Cl2] (R = H, R′ = H, 5a; R = Me, R′ = H, 5b; R = H, R′ = Me, 5c; R = Me, R′ = Me, 5d). A single-crystal X-ray study of 5a revealed a structure based on an octahedral geometry, such that the nitrogen of the mer-terdentate ligand is trans to the Cp and the two chloro ligands mutually trans. The single-crystal X-ray structures of 2a, 3a, 3b, 4a-CH3Cl3, and 5a are reported.
Total synthesis of the Cephalotaxus norditerpenoids (±)-cephanolides A-D
Haider, Maximilian,Sennari, Goh,Eggert, Alina,Sarpong, Richmond
supporting information, p. 2710 - 2715 (2021/03/01)
Concise syntheses of the Cephalotaxus norditerpenoids cephanolides A-D (8-14 steps from commercial material) using a common late-stage synthetic intermediate are described. The success of our approach rested on an early decision to apply chemical network analysis to identify the strategic bonds that needed to be forged, as well as the efficient construction of the carbon framework through iterative Csp2-Csp3 cross-coupling, followed by an intramolecular inverse-demand Diels-Alder cycloaddition. Strategic late-stage oxidations facilitated access to all congeners of the benzenoid cephanolides isolated to date.
A short route to access oxaspiro[: N,3,3]propellanes
Nassar, Youssef,Piva, Olivier
supporting information, p. 5811 - 5815 (2020/08/21)
Novel access to oxaspiro[n,3,3]propellanes has been developed from bicyclic lactones directly prepared by a photochemical hydroxymethylation or alternatively by a three-step sequence. Thanks to the presence of additional hydroxy- and propargylic groups, a second cyclization catalyzed by silver or bismuth salts, led to the propellane structure which was finally transformed into spiranic derivatives by a Simmons-Smith reaction or condensation with α-ketoesters.
Asymmetric total synthesis of ieodomycin B
Lin, Shuangjie,Zhang, Jianting,Zhang, Zhibin,Xu, Tianxiang,Huang, Shuangping,Wang, Xiaoji
, (2017/02/23)
Ieodomycin B, which shows in vitro antimicrobial activity, was isolated from a marine Bacillus species. A novel asymmetric total synthetic approach to ieodomycin B using commercially available geraniol was achieved. The approach involves the generation of 1,3-trans-dihydroxyl at C-3 and C-5 positions via a Crimmins-modified Evans aldol reaction and a chelation-controlled Mukaiyama aldol reaction of a p-methoxybenzyl-protected aldehyde, as well as the generation of a lactone ring in a deprotection-lactonization one-pot reaction.
New synthetic method of antibacterial natural product Ieodomycin B
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Paragraph 0038, (2017/10/26)
The invention discloses a new synthetic method of antibacterial natural product Ieodomycin B. The method includes the steps of taking a compound of the known formula 7 as a starting material, and synthesizing a target molecule through a series of reactions such as the Evans aldol reaction, the Weinreb amidation reaction, the methoxy benzyl protection reaction, the Mukaiyama aldol reaction, the cyclization reaction. The new synthetic method has the advantages of being unique and novel in design of the whole route, mild in reaction process and condition, high in speed, relatively little in side reaction, and easy and convenient to operate, and using conventional chemical reagents in the route so that the raw materials are cheap and easy to obtain, so as to reduce the synthetic cost greatly.
Synthesis of axially chiral 1,8-diarylnaphthalene ligands and application in asymmetric catalysis: An intriguing fluorine effect
Ghosh, Harisadhan,Vavilala, Ravishashidhar,Szpilman, Alex M.
, p. 79 - 84 (2015/02/19)
A fluorinated and a non-fluorinated axially chiral 1,8-diarylnaphthalene ligand have been synthesized through an Ullmann and Suzuki coupling reaction based strategy. A practical methodology for the successful chiral resolution of the newly synthesized catechol based moiety is presented. We also disclose the preliminary application of these axially chiral molecules as ligands in asymmetric transformation reactions.
Total Synthesis of (+)-7-epi-Tarchonanthuslactone via a Chelation-Controlled Mukaiyama Aldol Reaction
Huang, Shuangping,Liu, Dongwang,Tang, Linjun,Huang, Fei Fei,Zhang, Jianting,Wang, Xiaoji
, p. 1240 - 1247 (2015/03/30)
An asymmetric total synthesis of (+)-7-epi-tarchonanthuslactone was achieved from commercially available methyl (R)-3-hydroxybutyrate. The key step employed a diastereoselective chelation-controlled Mukaiyama aldol reaction to construct the chiral hydroxyl group at the C-5 position.
A general and enantioselective approach to pentoses: A rapid synthesis of PSI-6130, the nucleoside core of sofosbuvir
Peifer, Manuel,Berger, Rapha?lle,Shurtleff, Valerie W.,Conrad, Jay C.,Macmillan, David W. C.
supporting information, p. 5900 - 5903 (2014/05/20)
An efficient route towards biologically relevant pentose derivatives is described. The de novo synthetic strategy features an enantioselective α-oxidation reaction enabled by a chiral amine in conjunction with copper(II) catalysis. A subsequent Mukaiyama aldol coupling allows for the incorporation of a wide array of modular two-carbon fragments. Lactone intermediates accessed via this route provide a useful platform for elaboration, as demonstrated by the preparation of a variety of C-nucleosides and fluorinated pentoses. Finally, this work has facilitated expedient syntheses of pharmaceutically active compounds currently in clinical use.
The 'Mikami'-catalyst in enantioselective diels-alder reactions of juglone-based dienophiles with different 1-oxygenated dienes: An investigation on the substitution pattern dependent regioselectivity
B?se, Dietrich,Frey, Wolfgang,Pietruszka, J?rg
supporting information, p. 2524 - 2532 (2014/11/08)
A mechanistic study investigating the substitution pattern depending regioselectivity of enantioselective BINOL-Ti-catalyzed Diels-Alder reactions of juglone-based dienophiles with 1-oxygenated dienes is reported. The different influences of residues both on the diene as well as on the dienophiles are investigated giving a detailed picture of their role on the regioselectivity.
Lithium-titanium exchange of tertiary α-sulfonyl carbanions: Synthesis, structure, dynamics and reactivity of bis(1-sulfonylalkyl) titaniums
Hess, Thomas,Raabe, Gerhard,Gais, Hans-Joachim
, p. 7134 - 7147 (2015/03/04)
Lithium-titanium exchange of tertiary α-sulfonyl carbanions with ClTi(OiPr)3 and Cl2Ti(OiPr)2 in diethyl ether gave bis(1-sulfonylalkyl) titaniums and not the corresponding (1-sulfon-ylalkyl) titaniums. X-ray crystal structure analysis of di(iso-propoxy) bis[1-(phenylsulfonyl) cyclobutyl]titanium and di-(isopropoxy) bis[1-(phenylsulfonyl) isopropyl]titanium showed asymmetric distorted octahedral complexes, having hexaco-ordinate Ti atoms, two C-Ti bonds, four Ti-O bonds, and two four-membered Ti-O-S-Cα rings. According to 1H NMR spectroscopy bis(1-sulfonylcycloalkyl) titaniums are non-flux-ional at room temperature. This suggests that chiral bis(1-sulfonylalkyl) titaniums should be configurationally stable. The bis(1-sulfonylalkyl) titaniums are stable at room temperature towards β-H elimination. They selectively add to benzaldehyde in the presence of acetophenone but do not react with methyl iodide. The reaction of tertiary acyclic α-sulfonyl carbanions with ClTi(OiPr)3 in tetrahydrofuran (THF) gives different titanium derivatives with unspecified structures, which not only selectively react with benzaldehyde in the presence of acetophenone but are also alkylated by methyl iodide.
