Chiral N-Heterocyclic Carbene Ligands Bearing a Pyridine Moiety for the Copper-Catalyzed Alkylation of<i>N</i>-Sulfonylimines with Dialkylzinc Reagents
Amino acid‐derived chiral imidazolium salts, each bearing a pyridine ring, were developed as N‐heterocyclic carbeneligands. The copper‐catalyzed asymmetric alkylation of various N‐sulfonylimines with dialkylzincreagents in the presence of these chiral imidazolium salts afforded the corresponding alkylated products with high enantioselectivity (up to 99 % ee). The addition of HMPA to the reaction
Synthesis of Amidoalkyl Imidazol-2-ylidene Ligands and Their Application to Enantioselective Copper-Catalysed Conjugate Addition
作者:Neil Williams、Theo Moore、Mahboub Merzouk
DOI:10.1055/s-2007-1000832
日期:2008.1
imidazol-2-ylidene ligand was synthesised via a two-step procedure starting from commercially available amino alcohols. Preliminary screening of these bidentate ligands for the enantioselective copper-catalysed conjugateaddition of diethyl zinc to cyclohexenone revealed some moderate ee values. Related chiral iminoalkyl imidazole-2-ylidene ligands demonstrated much poorer enantioselectivity. The results
作者:Advait S Nagle、Ralph N Salvatore、Byong-Don Chong、Kyung Woon Jung
DOI:10.1016/s0040-4039(00)00330-0
日期:2000.4
beta-Aminoalcohols were smoothly converted to beta-amino bromides using thionyl bromide and DME which were easily isolated without any further purification. Participation by the beta-amino group in brominations not only enhanced reaction rates but also promoted stereo- and regioselectivities. (C) 2000 Elsevier Science Ltd. All rights reserved.