Enantioselective Syntheses
of 2-Substituted Pyrrolidines from Allylamines by Domino Hydroformylation-Condensation:
Short Syntheses of (<i>S</i>)-Nicotine and the
Alkaloid 225C
作者:Günter Helmchen、Pierre Dübon、Andreas Farwick
DOI:10.1055/s-0029-1217165
日期:——
2-substituted pyrrolidines based on rhodium-catalyzed hydroformylations of allylamines and their N-alkyl and N-acyl derivatives, which were prepared by asymmetric allylic substitutions, are described. The outcome of the hydrofonnylation reaction was controlled by the substituent at nitrogen, not by the substituent at carbon. In the case of N-alkylallylamines in situ reduction to the pyrrolidines occurred
A new phosphoramiditeligand was used in the iridium-catalyzed allylicsubstitution reaction. This permitted high regio- and enantioselectivities on a wide variety of substrates and nucleophiles. Because of the stereospecificity of the reaction obtained by using branched substrates, a kinetic resolution reaction was attempted. The origin of the impressive efficiency of this ligand in terms of kinetics
Superior performance of a chiral catalyst confined within mesoporous silica
作者:Brian F. G. Johnson、Stuart A. Raynor、Douglas S. Shephard、Thomas Mashmeyer、Thomas Mashmeyer、John Meurig Thomas、Gopinthar Sankar、Stefen Bromley、Richard Oldroyd、Lynn Gladden、Mike D. Mantle
DOI:10.1039/a902441g
日期:——
A chiral catalyst from the ligand 1,1′-bis(diphenylphosphino)ferrocene (dppf) anchored to the inner walls of the mesoporous support MCM-41 and co-ordinated to PdII has been shown to exhibit a degree of regioselectivity and enantiomeric excess, in the allylic amination of cinnamyl acetate, which is far superior to that of its homogeneous counterpart or that of a surface-bound analogue attached to a non-porous silica.
Application of iridium catalyzed allylic substitution reactions in the synthesis of branched tryptamines and homologues via tandem hydroformylation–Fischer indole synthesis
作者:Bojan P. Bondzic、Andreas Farwick、Jens Liebich、Peter Eilbracht
DOI:10.1039/b809143a
日期:——
reactions with a tandem hydroformylation-Fischer indole synthesis sequence as a highly diversity-oriented strategy for the synthesis of tryptamines and homologues was explored. This modular approach allows the substituents at C3 of the indole core, the type of the amine moiety, and the distance of the amine moiety to the indole core in the final synthetic step to be defined. The starting materials required
Rh(I)/Bisoxazolinephosphine-Catalyzed Regio- and Enantioselective Allylic Substitutions
作者:Wen-Bin Xu、Samir Ghorai、Wenyu Huang、Changkun Li
DOI:10.1021/acscatal.0c00712
日期:2020.4.17
Rhodium(I)/bisoxazolinephosphine combination has been developed as a general catalyst to achieve the dynamic kinetic asymmetric allylation of a variety of nitrogen, carbon, oxygen, and sulfur pronucleophiles from branched racemic allylic carbonates. Exclusive branch-selectivity and up to 99% enantiomeric excess could be obtained under neutral conditions. Linear allylic substrates (both Z and E) could