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
Bis(oxazoline) and Bis(oxazolinyl)pyridine Copper Complexes as Enantioselective Diels−Alder Catalysts: Reaction Scope and Synthetic Applications
作者:David A. Evans、David M. Barnes、Jeffrey S. Johnson、Thomas Lectka、Peter von Matt、Scott J. Miller、Jerry A. Murry、Roger D. Norcross、Eileen A. Shaughnessy、Kevin R. Campos
DOI:10.1021/ja991191c
日期:1999.8.1
the use of this chiral catalyst in more complex Diels−Alder processes, are described. Similarly, the cationic coppercomplex 9a, [Cu((S,S)-t-Bu-pybox)](SbF6)2, is effective in the Diels−Alder reactions of monodentate acrolein dienophiles while the closely related complex, 9d [Cu((S,S)-Bn-pybox)](SbF6)2, is the preferred Lewis acid catalyst for acrylate dienophiles in reactions with cyclopentadiene.