BINAPS - An axially chiral P,S-heterodonor ligand for asymmetric catalysis based on binaphthalene backbone

Abstract

The chelating P,S-heterodonor ligand 2-diphenylphosphanyl-1,1'-binaphthalene-2'-thiol (11) (BINAPS), which features a chiral axis as the unique stereogenic element, has been prepared in both racemic and enantiopure form through a multistep reaction sequence using 2,2'-dihydroxy-1,1'-binaphthalene (BINOL) as the starting material. The reaction sequence is completely stereoconservative and (S)-11 is obtained with no loss of enantiopurity from pure (S)-BINOL. (R)-11 can be alternatively obtained by resolution of racemic 11 using the chiral (S)-benzylaminato Pd(II)-complex 19 as the resolving agent. The S-methyl or the S-i-propyl derivatives 14 have been used as chiral ligands in the Rh(I)-catalyzed asymmetric hydroformylation of styrene and in the hydrogen transfer reduction of acetophenone with modest success (up to 20% ee). In the presence of suitable Pd-complexes the same ligands provide higher ees in the hydrosilylation of styrene (50% ee) and in the allylic alkylation of 1,3-diphenylprop-2-enyl acetate (60% ee).Key words: heterodonor ligands, binaphthalene derivatives, enantioselective catalysis, transition metal catalysts, allylic alkylation.

Chiral Complexes of RhI Containing Binaphthalene‐Core P,S‐Heterobidentate Ligands − Synthesis, Characterization, and Catalytic Activity in Asymmetric Hydrogenation of α,β‐Unsaturated Acids and Esters

“…[11] The preparation of the enantiopure complexes 3a and 3b was accomplished as reported in Scheme 1 by treating the rhodium complex [Rh(NBD)(THF) 2 ] ϩ BF 4 Ϫ (2) (NBD ϭ 1,4-norbornadiene) with a stoichiometric amount of (S)-1a and (S)-1b, respectively. The required intermediate adduct 2 was prepared in situ from the corresponding chloro-bridged dimer [Rh(NBD)Cl] 2 and AgBF 4 .…”

“…The ligands, (S)-2-(diphenylphosphanyl)-2Ј-(methylthio)-1,1Ј-binaphthalene (1a) and (S)-2-(diphenylphosphanyl)-2Ј-(isopropylthio)-1,1Ј-binaphthalene (1b), were prepared as previously reported. [11] The ees of the samples from the catalytic runs were determined with a Hewlet Packard 5890A gas chromatograph fitted with a 25-m capillary column coated with diethyl tert-butylsilyl-β-cyclodextrin PS 086 (i.d. 0.25 mm), purchased from MEGA (Legnano, Italia), using He as the carrier (head pressure 60 kPa, split ratio 100).…”

“…Recently, we reported on the synthesis of BINAPS, [9] a heterobidentate version of BI-NAP in which one of the two diphenylphosphanyl substituents is replaced by an alkylthio group. BINAPS derivatives performed well in some Pd-catalysed asymmetric reactions, such as allylic alkylation [10] and hydrosilylation, [11] but were less satisfactory in Rh-catalysed processes such as hydroformylation and H-transfer reduction. [11] We report here on further investigations into the preparation, dynamic behaviour and utilization in enantioselective hydrogenation of such BINAPS-based Rh complexes.…”

Preparation of S-Containing Aminophosphine and Phosphoramidite Ligands and Their Applications in Enantioselective C–C Bond Forming Reactions

“…These P/S ligands were successfully applied in Pd-catalyzed enantioselective C-C bond forming reactions. In addition, axially chiral P/S heterdonor ligands, BINAPS, bearing excellent catalytic effects were reported by She [24], Gladiali [25] and Shi [26].…”

Palladium-catalyzed asymmetric allylic substitutions by axially chiral P,S-, S,S-, and S,O-heterodonor ligands with a binaphthalene framework

“…8 Reduction of compound 4 was carried out by HSiCl 3 in the presence of Et 3 N in toluene at 120°C to obtain P,S-heterodonor ligand L1. The S,S-heterodonor ligands L2-L4 were easily prepared by heating compounds 9 and L1 with sulfur at 120°C.…”