Chiral C2-symmetric bisferrocenyldiamines as ligands for transition metal catalyzed asymmetric cyclopropanation and aziridination

A new series of chiral C-2-symmetric bisferrocenyldiimine 1 and bisferrocenyldiamines 2 and 3 proved to be efficient ligands for the copper(I)-catalyzed asymmetric cyclopropanation, cyclopropenation, and aziridination of alkenes and alkynes to give high diastereo- and enantioselectivity as well as high chemical yields. In some instances the enantiomeric excesses of cyclopropanated products are among the highest (>97% ee) ever reported. Comparative studies show that stereoselectivity depends highly on the steric variation both in the ligand and the substrate. Other transition metal complexes incorporating some of these ligands such as Ru(3c)Cl-2, [(NBD)Rh(2)]ClO4, [Cu(2)(MeCN)(2)]PF6, and Pd(2)Cl-2 also demonstrated high enantioselectivity in cyclopropanation reactions. (C) 1999 Elsevier Science Ltd. All rights reserved.