Early Transition Metal Alkoxide Complexes Bearing Homochiral Trialkanolamine Ligands
摘要:
Enantiomerically pure trialkanolamines of the formula N(CH(2)CHROH)(3), where R = methyl (3a), cyclohexyl (3b), tert-butyl (3c), or phenyl (3d), are readily synthesized by the reaction of ammonia with 3 equiv of an enantiopure epoxide. Trialkanolamines 3a-d replace n-propanol in tri-n-propyl vanadate to afford corresponding complexes 4a-d of the formula LV=O, where L is the deprotonated trialkanolamine. Similarly, (S,S,S)-triisopropanolamine 3a reacts with Ti((OPr)-Pr-i)(4) to produce monomeric LTi((OPr)-Pr-i), 7a, which upon treatment with acetyl chloride gives the chloro complex LTiCl, 7b. The later group 5 ethoxides react with 3a to produce LM(OEt)(2) (M = Nb, Ta). Partial hydrolysis of the Nb and Ta derivatives produces tetrameric mu-oxo-bridged structures which retain the trialkanolamine ligands. In all complexes the transition metal resides in a highly asymmetric environment, suggesting that this class of complexes may find use in the field of asymmetric catalysis. The X-ray crystal structures of complexes 4c and 7b are reported.
Use of electrospray ionization mass spectrometry to characterize chiral reactive intermediates in a titanium alkoxide mediated sulfoxidation reaction
作者:Marcella Bonchio、Giulia Licini、Giorgio Modena、Stefano Moro、Olga Bortolini、Piero Traldi、William A. Nugent
DOI:10.1039/a701227f
日期:——
The ESIMS technique, combined with
1
H NMR evidence, provides
a precise inventory of the catalytic Ti
IV
precursors and the
characterization of the reactive peroxometal complex involved in
enantioselective sulfoxidation employing the
Ti
IV
–homochiral trialkanolamine–alkylhydroperoxide
system.
ESIMS 技术与 1 H NMR 证据相结合,提供了催化 Ti IV 前体的精确清单,并描述了采用 Ti IV - 同手性三烷醇胺 - 烷基过氧化氢体系进行对映选择性硫氧化作用时所涉及的活性过氧金属复合物的特征。
Early Transition Metal Alkoxide Complexes Bearing Homochiral Trialkanolamine Ligands
作者:William A. Nugent、Richard L. Harlow
DOI:10.1021/ja00093a011
日期:1994.7
Enantiomerically pure trialkanolamines of the formula N(CH(2)CHROH)(3), where R = methyl (3a), cyclohexyl (3b), tert-butyl (3c), or phenyl (3d), are readily synthesized by the reaction of ammonia with 3 equiv of an enantiopure epoxide. Trialkanolamines 3a-d replace n-propanol in tri-n-propyl vanadate to afford corresponding complexes 4a-d of the formula LV=O, where L is the deprotonated trialkanolamine. Similarly, (S,S,S)-triisopropanolamine 3a reacts with Ti((OPr)-Pr-i)(4) to produce monomeric LTi((OPr)-Pr-i), 7a, which upon treatment with acetyl chloride gives the chloro complex LTiCl, 7b. The later group 5 ethoxides react with 3a to produce LM(OEt)(2) (M = Nb, Ta). Partial hydrolysis of the Nb and Ta derivatives produces tetrameric mu-oxo-bridged structures which retain the trialkanolamine ligands. In all complexes the transition metal resides in a highly asymmetric environment, suggesting that this class of complexes may find use in the field of asymmetric catalysis. The X-ray crystal structures of complexes 4c and 7b are reported.
Syndiotactic polystyrene with very high molecular weight produced by sterically and electronically modified catalyst
作者:Youngjo Kim、Youngkyu Do
DOI:10.1016/s0022-328x(02)01555-3
日期:2002.8
A new type of the half-metallocene catalysts for the syndiospecific polymerization of styrene was prepared by the reaction of various kinds of trialkanolamine with Cp*TiCl3 in the presence of triethylamine. All seven compounds have a highly thermal stability and they show fairly good activities in the presence of cocatalyst MMAO in styrene polymerization. Especially, highly bulky and electronically deficient 7/MMAO system affords syndiotactic polystyrene with very high molecular weight. (C) 2002 Published by Elsevier Science B.V.
Highly regioselective microwave-assisted synthesis of enantiopure C3-symmetric trialkanolamines
作者:Laura Favretto、William A. Nugent、Giulia Licini
DOI:10.1016/s0040-4039(02)00306-4
日期:2002.4
Enantiopure, C-3-symmetric trialkanolamines can be efficiently and rapidly obtained on a gram scale via one pot or step-wise microwave-assisted epoxide ring opening with ammonia in high yields (up to 89%) and regioselectivity up to 100%. (C) 2002 Elsevier Science Ltd. All rights reserved.
Enantiomeric programming in tripodal transition metal scaffolds
作者:Nicholas C. Fletcher、Ciarán Martin、Heather J. Abraham
DOI:10.1039/b703761a
日期:——
A new route to the isolation of the enantiopure tris-chelate complex (Δ/Λ)-fac-[Ru(L1)3]2+
(where L1 is 2,2′-bipyridine-5-carboxylic acid) is demonstrated, where the transition metal centre retains the memory of the chirality present in a simple tripodal tether used to control the metal centred geometry.