Enantiomerically divergent pathways in Tsuji-Trost reactions: exploiting the structural differences between β-acyloxy-o-(diphenylphosphino)benzamides and β-amido-o-(diphenylphosphino)benzoates
摘要:
Using a single chiral scaffold, (1R,2S)-norephedrine, a series of monophosphine ligands have been prepared. The ligands prepared, beta-acyloxy-(o-diphenylphosphino)amides and beta-amido-(o-diphenylphosphino)esters, give rise to enantiomerically divergent products in the Tsuji-Trost asymmetric allylic reaction. The phosphinoamides afforded the best enantioselectivities and favored the (S)-enantiomer of the product. In contrast the phosphinoesters afforded lower enantioselectivities and favored the (R)-enantiomer. A mechanistic rationale for this observation is proposed. (C) 2016 Elsevier Ltd. All rights reserved.
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.
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.