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.
Rhodium-Catalyzed Reactions of Dithiols and 1,4-Bis(bromomethyl)benzenes Leading To Enantioenriched Dithiaparacyclophanes
We have achieved the first catalytic enantioselective synthesis of planar-chiral dithiaparacyclophanes by means of cationic rhodium(I)/(S)-BINAPHANE complex-catalyzed reactions of dithiols and 1,4-bis(bromomethyl)benzenes. The present method represents the first example of asymmetric synthesis of planar-chiral cyclophanes through catalytic enantioselective construction of the ansa chains.