Asymmetric synthesis of planar-chiral paracyclophanes by double C–S bond formation: comparison of catalytic activity and enantioselectivity of Pd and Rh catalysts
作者:Tomoko Hori、Yu Shibata、Ken Tanaka
DOI:10.1016/j.tetasy.2010.04.008
日期:2010.5
We have determined that a cationic palladium(II)/(R)-BINAP complex is able to catalyze enantioselective double C-S bond-forming reactions between dithiols and dibenzyl dibromides leading to planar-chiral dithiaparacyclophanes. Although the yields and ee values of the palladium(II)-catalyzed syntheses of dithiaparacyclophanes did not exceed our previously reported cationic rhodium(I)/(S)-BINAPHANE complex-catalyzed ones, the palladium(II)-catalyzed reactions allowed the use of commercially available and inexpensive (R)-BINAP as a ligand. On the other hand, an almost racemic product was obtained by using a cationic rhodium(I)/(R)-BINAP complex as a catalyst. (C) 2010 Elsevier Ltd. All rights reserved.