Reuse of chiral cationic Pd–phosphinooxazolidine catalysts in ionic liquids: highly efficient catalytic asymmetric Diels–Alder reactions
作者:Kouichi Takahashi、Hiroto Nakano、Reiko Fujita
DOI:10.1039/b611228e
日期:——
Chiral cationic palladium-phosphinooxazolidine catalysts in ionicliquid afforded excellent enantioselectivity in Diels-Alder reactions and the catalyst was easily recycled eight times without any significant decrease in chemical yields or enantioselectivity (89-99%, 88-99% ee).
Cationic palladium (Pd)- and platinum (Pt)-phosphinooxazolidine catalysts 13a-c, 15a-d, 17a-c, and 19a-c were prepared from phosphinooxazolidine ligands 1-3, MCl2 (M = Pd and Pt), and counterions, and the activities of the catalysts in the asymmetric Diels-Alder (DA) reactions of cyclic or acyclic dienes with imide dienophiles were investigated. These catalysts demonstrated high levels of catalytic activity. The cationic Pd-POZ complex 13c provided particularly excellent enantioselectivity (98% ee) in the DA reactions of cyclopentadiene with acryloyl-, crotonyl-, and fumaroyl-1,3-oxazolidin-2-ones (20a-c).
Cationic bis(oxazoline)Cu(II) Lewis acid catalysts. Enantioselective furan Diels-Alder reaction in the synthesis of ent-shikimic acid
作者:David A. Evans、David M. Barnes
DOI:10.1016/s0040-4039(96)02259-9
日期:1997.1
The highly enantioselective Diels-Alder reaction between acryloyl oxazolidinone and furan, catalyzed by cationic bis(4-tert-butyloxazoline)Cu(II) complex 1, is presented. Though the reaction equilibrates rapidly at -20 degrees C, reaction at -78 degrees C permits isolation of the kinetic product mixture. The synthetic utility of the reaction is demonstrated by the conversion of the cycloadduct to ent-shikimic acid. Copyright (C) 1996 Published by Elsevier Science Ltd