Feringa’s ligands

Woodward and co-workers recently achieved catalytic enantioselective alkylation of aldehydes with (R3Al)2 DABCO complexes or R3A1 (R = Me or Et) in the presence of Ni(acac)2/Feringa s ligand 196 (Equation (81 )).439... 

Scheme 5.2 Hydrovinylation of vinylarenes with an in situ generated nickel catalyst from a phosphoramidite ligand derived from Feringa s ligand.

Najera et al. have shown that Feringa s phosphoramidite ligand 102 is superior to other ligands in the cycloaddition of aryl iminoesters 62 with tert-butyl acrylate (106), /V-methylphthalimide 114, and diisopropyl fumarate (118).57 As shown in Scheme 2.31 and Table 2.9, the products 116 and 117 were formed in excellent yields and exquisite endo selectivity. 

After the initial report from the Leither group/ other Feringa-type ligands, such as (S,7 a)-H5 and (S, S, f a)-L16, have been developed and utilized in the asymmetric hydrovinylation of styrenes (Scheme 9.4). Meanwhile, a wide range of Lewis acids were evaluated for their ability to activate the Ni precursor in asymmetric hydrovinylation of styrene. Among these activators, Inij appears to be a potent candidate of choice since it can lead to the same chemo- and enantioselectivity and even higher activity than the benchmark system based on NaBARF. ... 

The above powerful methodology was applied to the synthesis of both steroid C20 (S ) and C20 (R) derivatives from the corresponding 1,3-dienes 8 and 9 derived from two prototypical steroids, estrone and 3-epiandrosterone. By the proper choice of ligands between Feringa s phosphoramidite ligand and another phosphoramidite ligand (S,S)-10, the authors showed that it was possible to install with complete stereoselectivity either the C20 (i ) or C20 (S) configuration. As shown in Scheme 5.12, the nickel-catalysed... 

Following the work presented previously by Feringa s group, Du and Cao [21] applied bisnaphthyl-based chiral dienes as the steering ligand for the enantioselective arylation of the same substrate type (A Z f-dimethylsulfamoyl-protected aldimines) with arylboronic acids, providing the desired products in moderate-to-good yields and up to 84% ee (Scheme 6.16). 

A remarkable kinetic resolution was observed recently by Feringa and coworkers when 2-silyloxyfuran was reacted with the racemic unsymmetrical allylic substrate 86, catalyzed by the palladium complex of Trost s ligand (/ ,/ )-14, as illustrated in Scheme 5.28. The acetate anion liberated upon oxidative addition of palladium(O) is assumed to cleave the silyl protecting group, so that the enolate anion forms aside from TMSOAc. After allylic alkylation of that enolate, double bond migration leads to butenolide (R)-87 isolated in 47%, if the reaction was run with 52% conversion. Not only the product 87 but also the recovered acetate... 

Scheme 5.87 Feringa s enantioselective Relbrmatsky reaction mediated by BINOL-type ligand 315.

In 1993, Alexakis et al. reported the first copper-catalyzed asymmetric conjugate addition of diethylzinc to 2-cyclohexenone using phosphorous ligand 28 (32% ee).36 An important breakthrough was achieved by Feringa et al. with chiral phosphoramidite (S,R,R)-29 (Figure 1), which showed excellent selectivity (over 98% ee) for the addition of 2-cyclohexenone.37 Since then, efficient protocols for the conversion of both cyclic and acyclic enones, as well as lactones and nitroalkenes, have been developed featuring excellent stereocontrol. 

Feringa and co-workers applied chiral phosphoramidite ligand (S,R,R)-67 in the conjugate addition of dimethylzinc to acyclic unsaturated malonates 68 and obtained up to 98% ee (Scheme 22).71... 

The enantioselective conjugate addition of dialkylzinc to nitroalkenes using other phosphoramidite,79,79a 83a sulfonamide,84 and binaphthol-based thioether ligands65 has also been studied in the past few years. Particularly noteworthy are the efficient chiral monodentate phosphoramidite ligands (S,R,R)-29 and (A,A)-55 developed by Feringa et al. and Alexakis et al., respectively, for this reaction. (S,R,R)-29 provided excellent enantioselectivities (up to 98% ee) for acyclic nitroalkenes (Scheme 25).80 It also worked well for other nitroolefin substrates such as 3-nitrocoumarin 7068 and methyl 3-nitropropenoate 7185. 

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