Highly exo-selective and enantioselective cycloaddition reactions of nitrones catalyzed by a chiral binaphthyldiimine-Ni(II) complex.
[reaction: see text] Significant levels of exo-selectivity (exo:endo = >99:1 to 86:14) and enantioselectivity (95-82% ee) were obtained in the 1,3-dipolar cycloadditions of a number of nitrones with 3-(2-alkenoyl)-2-thiazolidinethiones, using the chiral binaphthyldiimine-Ni(II) complex (5-20 mol %), which was easily prepared form N,N'-bis(3,5-dichrolo-2-hydroxybenzylidene)-1,1'-binaphthyl-2,2'-diamine and Ni(ClO4)2 x 6H2O in CHCl3 in the presence of 4 A molecular sieves, as a chiral Lewis acid catalyst.
Suga
Hiroyuki
H
Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, Wakasato, Nagano 380-8553, Japan. sugahio@shinshu-u.ac.jp
Nakajima
Takuya
T
Itoh
Kengo
K
Kakehi
Akikazu
A