762-99-2Relevant articles and documents
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.
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.
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.
