Catalytic asymmetric transformations with fine-tunable biphenol-based monodentate ligands
摘要:
A library of new fine-tunable monodentate phosphite and phosphoramidite ligands based on chiral biphenol have been designed and developed. These monodentate phosphorus ligands have exhibited excellent enantioselectivity in the Pd-catalyzed asymmetric allylic alkylation and Rh-catalyzed asymmetric hydrogenation. (c) 2006 Elsevier Ltd. All rights reserved.
Highly Enantioselective Copper-Catalyzed Allylic Alkylation with Phosphoramidite Ligands
作者:Anthoni W. van Zijl、Leggy A. Arnold、Adriaan J. Minnaard、Ben L. Feringa
DOI:10.1002/adsc.200303207
日期:2004.3
New phosphoramidites were applied as chiral ligands in the Cu-catalyzed allylicalkylation with dialkylzinc reagents. A variety of substrates, reagents and chiral ligands were screened, resulting in improved catalytic methodology for allylic bromides in which enantioselectivities up to 88% were reached.
Rh-Catalyzed Enantioselective Conjugate Addition of Arylboronic Acids with a Dynamic Library of Chiraltropos Phosphorus Ligands
作者:Chiara Monti、Cesare Gennari、Umberto Piarulli
DOI:10.1002/chem.200600960
日期:2007.2.2
99 % ee) and excellent yields were obtained in the addition to either cyclic or acyclic substrates. The flexible biphenolic P ligands outperformed the analogous rigid binaphtholic P ligands. Variable-temperature (31)P NMR studies revealed that the biphenolic ligands are tropos even at low temperature. Only below 190 K was a coalescence observed; upon further cooling, two atropisomers were detected. The
The successful example of chiral formamides that function as asymmetriccatalysts is described. (S,S)-N,N-Bis(α-methylbenzyl)formamide mediates the enantioselective addition of allyl- and crotyltrichlorosilanes to aliphatic aldehydes with the assistance of hexamethylphosphoramide (HMPA) to afford the corresponding homoallylic alcohols in up to 98% enantiomeric excess.
Copper-Catalyzed Asymmetric Conjugate Addition with Chiral SimplePhos Ligands
作者:Laëtitia Palais、Alexandre Alexakis
DOI:10.1002/chem.200901577
日期:2009.10.12
they can be highly functionalised. Herein we report the copper‐catalysed asymmetricconjugateaddition of diethyl zinc and trialkylaluminium reagents with SimplePhos ligands, which gives high enantioselectivity with cyclic enones, acyclic enones and nitro‐olefins, with up to 98.6 % ee. Of particular interest is the reaction of trialkylaluminium reagents with a wide range of 3‐substituted enones, thus
Rh-Catalyzed Asymmetric Hydrogenation of Prochiral Olefins with a Dynamic Library of Chiral TROPOS Phosphorus Ligands
作者:Chiara Monti、Cesare Gennari、Umberto Piarulli、Johannes G. de Vries、André H. M. de Vries、Laurent Lefort
DOI:10.1002/chem.200500464
日期:2005.11.4
A library of 19 chiraltroposphosphorusligands, based on a flexible (tropos) biphenol unit and a chiral P-bound alcohol (11 phosphites) or secondary amine (8 phosphoramidites), was synthesized. These ligands were screened, individually and as a combination of two, in the rhodium-catalyzed asymmetrichydrogenation of dehydro-alpha-amino acids, dehydro-beta-amino acids, enamides and dimethyl itaconate