ChemInform Abstract: Axially Dissymmetric Diphosphines in the Biphenyl Series: Synthesis of (6,6′‐Dimethoxybiphenyl‐2,2′‐diyl)bis(diphenylphosphine) (“MeO‐BIPHEP”) and Analogues via an ortho‐Lithiation/Iodination Ullmann Reaction Approach.

Abstract

The new axially dissymmetric diphosphines (R)-and (S)-(6,6-dimethoxybiphenyl-2,2'-diyl)bis(diphenyl phosphine) ((R)-and ( S p a ; 'MeO-BIPHEP) and the analogues (R)-and (S)-Sb and Sc have been synthesized in enantiomerically pure form. These ligands have become readily available by a synthetic scheme which employs, as key steps, an ortho-lithiation/iodination reaction of the (m-methoxypheny1)diphenylphosphine oxides 8 and a subsequent Ullmunn reaction of the resulting iodides 9 to provide the racemic bis(phosphine oxides) 10. The bis(phosphine oxides) 10 subsequently are resolved with (-)-(2R,3R)-and (+)-(2S,3S)-0-2,3-dibenzoyltartaric acid and reduced to diphosphines 5. The Ullmann reaction constitutes a new and efficient route to 2,2'-bis(phosphinoy1)-substituted biphenyl systems. Absolute configurations were established for (R)-Sa by X-ray analysis of the derived Pd complex (R,R)-17a, and for Sb and 5c by means of 'H-NMR comparisons of the derived Pd complexes 16 or 17, respectively, and by means of CD comparisons. The MeO-BIPHEP diphosphine 5a proved to be as efficient as the previously described BIPHEMP diphosphine ((6,6'-dimethylbiphenyl-2,2'-diyl)bis(diphenylphosphine)) in enantioselective isomerizations and hydrogenations.1. Introduction. -The potential of axially dissymmetric diphosphines such as the prototype compound BINAP (1) as asymmetry-inducing ligands has been amply demonstrated for various transition-metal-catalyzed reactions, in particular for Rh'-and RUT'-catalyzed hydrogenations [ 11. Therefore, it is not surprising that considerable efforts have been undertaken for the design and synthesis of other atropisomeric diphosphine ligands. Some time ago, the parent compound in the atropisomeric biphenyl series, the BIPHEMP ligand 2a has been synthesized by us [2] as well as independently by Freyd and coworkers [3], and by Miyashita et al. [4]. Moreover, the substituted analogues 2b, 2c, and the bridged analogue 3 have also been synthesized [2]. The BIPHEMP ligand was shown to be at least as efficient as the BINAP ligand in Rhl-catalyzed allylamine-to-enamine isomerizations [2] and in Ru"-catalyzed hydrogenations of allylic alcohols and P-keto

Copper polyhydrides: A powerful tool in chemical synthesis. Stryker’s reagent in perspective

“…The results obtained by Bruce H. Lipshutz and his co-workers have been very satisfactory. For example, in the asymmetric synthesis of hydroxylated-1,4 esters, PMHS and special phosphine group of auxiliary ligands are used such as the BIPHEP [64] series of ligands, the (R,S)-JOSIPHOS [65] (commercially available from Solvias Group, reference: CAS: 155806-35-2, Solvias: SL-J 0 01-1) and the SEGPHOS [66] family of ligands, whose structures are shown in Figure 6.…”

Enantioselective liquid‐liquid extraction of DL‐mandelic acid using chiral diphosphine ligands as extractants

“…(S)-MeO-BIPHEP was prepared in lab referring the route from literature. 27 The reagents and chemicals (analytic grade unless stated otherwise) were purchased from Sinopharm Chemical Reagent Co, Ltd, and Tianjin Damao Chemical Reagent Co, Ltd (China).…”

Recent Advances in the Application of Chiral Phosphine Ligands in Pd-Catalysed Asymmetric Allylic Alkylation

“…Furthermore, they have been especially successful with allylic substrates that have proven difficult to control with other ligand systems [ 6 , 7 , 8 , 9 , 10 , 11 ]. Axially chiral ligands such as BINAP [ 39 ], BIHEP [ 40 ], MeO-BIHEP [ 41 ], BICHEP [ 42 ], SEGPHOS [ 43 ], SYNPHOS [ 44 , 45 ], TunaPHOS [ 46 ], tetraME-BITANP [ 47 ], tetra-BITIOP [ 48 ] and P-PHOS [ 49 ], have shown an excellent asymmetric induction, particularly in palladium-catalysed allylic alkylation.…”