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標題: Synthesis, characterization, and structures of arylaluminum reagents and asymmetric arylation of aldehydes catalyzed by a titanium complex of an N-sulfonylated amino alcohol
作者: Zhou, S.L.
Chuang, D.W.
Chang, S.J.
Gau, H.M.
關鍵字: highly enantioselective addition
aryl transfer-reactions
2 stereogenic
conjugate addition
phenyl transfer
oxovanadium(v) complexes
diphenylzinc additions
organozinc reagents
期刊/報告no:: Tetrahedron-Asymmetry, Volume 20, Issue 12, Page(s) 1407-1412.
摘要: A series of phenylaluminum reagents AlPh(x)Et(3-x)(L) (x = 1-3) containing adduct ligand L [Et(2)O, THF, OPPh(3), or 4-dimethylaminopyridine (DMAP)] were synthesized and characterized. NMR studies showed that AlPh(x)Et(3-x)(L) (x = 1 or 2) exists as an equilibrium Mixture of 3-4 species in Solution. Solid-state structures of the phenylaluminum In reagents reveal a distorted tetrahedral geometry. Asymmetric additions of phenylaluminum to 2-chlorobenzaldehyde were examined employing a titanium(IV) complex [TiL*(OPr(2)(i)](2) 10 (H(2)L* = (1R,2S)-2-(p-tolylsulfonylamino)-1,3-diphenyl-1-propanol) as a catalyst precursor. It was found that the adduct ligand L had a strong influence oil the reactivity and the enantioselectivity in asymmetric phenyl additions to aldehydes. The phenylaluminum reagents with OPPh(3) or DMAP were unreactive toward aldehydes, and AlPh(3)(THF) was found to be superior to AlPh(3)(OEt(2)) or AlPhEt(2)(THF). Asymmetric aryl additions of AlAr(3)(THF) to aldehydes employing a loading of 5 mol % titanium(IV) complex 10 with a strategy of a slow addition of the aldehydes over 20 min were conducted. and the reactions produced optically active secondary alcohols in high yields with excellent enantioselectivities Of up to 94% ee. (C) 2009 Elsevier Ltd. All rights reserved.
ISSN: 0957-4166
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