Search

Rhodium‐catalyzed hydroformylation of olefins is an important method for synthesizing aldehydes, and it is worth noting that regioselectivity and enantioselectivity of the product controlled by ligand are the most commonly used strategies. The modular synthesis of phosphite and phosphoramidite ligands have significant advantages of simple synthesis and high catalytic activity, which was why these ligands have been widely used in hydroformylation reactions. Herein, we focus on the synthesis methods and design ideas of such ligands, as well as their application effects in hydroformylation reactions. This review aims to provide a reference for the design and synthesis of ligands in hydroformylation subsequently. [ABSTRACT FROM AUTHOR]

In this article we demonstrate how asymmetric total synthesis of (S)-rivastigmine has been achieved using direct asymmetric reductive amination as the key transformation in four steps. The route started with readily available and cheap m-hydroxyacetophenone, through esterification, asymmetric reductive amination, N-diphenylmethyl deprotection and reductive amination, to provide the final (S)-rivastigmine in 82% overall yield and 96% enantioselectivity. In the asymmetric reductive amination, catalysed by the iridium-phosphoramidite ligand complex and helped by some additives, the readily prepared 3-acetylphenyl ethyl(methyl)carbamate directly reductively coupled with diphenylmethanamine to yield the chiral amine product in 96% ee and 93% yield. [ABSTRACT FROM AUTHOR]

Cooperative catalysis by [Pd(dba)2] and the chiral phosphoric acid BA1 in combination with the phosphoramidite ligand L8 enabled the efficient enantioselective amination of racemic allylic alcohols with a variety of functionalized amines. This catalytic protocol is highly regio- and stereoselective (up to e.r. 96:4) and furnishes valuable chiral amines in almost quantitative yield. [ABSTRACT FROM AUTHOR]

The virtue of enantiomers: A general method has been developed for measuring the individual contributions of noncovalent interactions within transition‐metal complexes and dissecting them from electronic effects. On Pd complexes with one enantiopure and two enantiomeric phosphoramidite ligands, it was experimentally shown that modulations in extended CH–π and π–π interaction interfaces provide a ΔΔG value that is significant for stereoselection. [ABSTRACT FROM AUTHOR]

A highly enantioselective copper-catalyzed conjugate addition with triethylaluminium was developed using phosphoramidite ligands bearing a D2-symmetric biphenyl backbone. For these ligands we demonstrated that the 3,3′,5,5′-substituents on the biphenyl backbone can completely reverse the absolute configuration of the products. [ABSTRACT FROM AUTHOR]

Abstract: Copper-catalyzed intramolecular conjugate addition–cyclization in the presence of chiral phosphoramidite ligands was described. Cyclic products with multiple chiral centers were obtained with up to 93:7 diastereomeric ratio and 94% ee. [Copyright &y& Elsevier]

Abstract: Only a limited number of ligands have been successfully employed for the Ni-catalyzed asymmetric hydrovinylation reaction. Diarylphosphinites, carrying β-acylamino groups prepared from readily available carbohydrates, in conjunction with highly dissociated counteranions {[(3,5-(CF3)2C6H3]4B− or SbF6 −}, effect the hydrovinylation of vinylarenes under ambient pressure of ethylene with high enantioselectivity. Nitrogen substituents such as –COCF3 and COPh groups lead to isomerization of the primary products (3-arylbutenes) to Z- and E-2-aryl-2-butenes. In a prototypical synthesis of a 2-arylproionic acid, (S)-3-(4-bromophenyl)-1-butene (89% ee) has be transformed into (R)-ibuprofen by Ni-catalyzed cross-coupling with i-BuMgBr, followed by oxidation of the double bond with NaIO4 and KMnO4. Asymmetric codimerization of norbonene and ethylene using binaphthol-derived phosphoramidites as ligands gives 1:1, 2:1 or polymeric adducts depending on the relative configurations and nature of the BINAP and amine moieties. With one of the phosphoramidite–Ni complexes, counteranions BAr4 − [Ar=3,5-(CF3)2C6H3] and SbF6 −, which had been used interchangeably in other reactions, give either a 1:1 adduct or a 2:1 adduct, respectively. [Copyright &y& Elsevier]

The axially chiral BICOL backbone was functionalised with two third generation carbosilane dendritic wedges and further elaborated to a phosphoramidite ligand. High enantioselectivities were obtained when these monodentate ligands were applied in the rhodium-catalysed asymmetric hydrogenation of methyl 2-acetamidocinnamate. [Copyright &y& Elsevier]