β-Hydroxy and β-(o-diphosphino)benzoyloxy(o-diphosphino) benzamides as ligands for asymmetric allylic alkylation
摘要:
Diphenylphosphinobenzoic acid was treated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), DMAP, and with either one of two equivalents of (1R,2S)-norephedrine and (1S,2S)-pseudonorephedrine. This process yielded a series of beta-hydroxy and beta-(diphosphino) benzoyloxy(diphosphino)benzamides that were employed in the Tsuji-Trost asymmetric allylic alkylation process. It was determined that the diastereomeric geometry of the norephedrine series was superior to that of the pseudonorepliedrine-based ligands. In addition, it was determined that the norephedrine-based beta-(o-diphosphino)benzoyloxy(o-diphosphino)benzamide afforded the best enantiomeric ratio (94:6) favoring the (S)-enantiomer. (C) 2009 Elsevier Ltd. All rights reserved.