BINAP axial chirality

The numerous chiral phosphine ligands which are available to date [21] can be subclassified into three major categories depending on the location of the chiral center ligands presenting axial chirality (e.g., BINAP 1 and MOP 2), those bearing a chiral carbon-backbone (e.g., DIOP 3, DuPHOS 4), and those bearing the chiral center at the phosphorus atom (e. g., DIPAMP 5, BisP 6), as depicted in Fig. 1. 

Table 3.12 surveys current industrial applications of enantioselective homogeneous catalysis in fine chemicals production. Most chiral catalyst in Table 3.12 have chiral phosphine ligands (see Fig. 3.54). The DIP AMP ligand, which is used in the production of L-Dopa, one of the first chiral syntheses, possesses phosphorus chirality, (see also Section 4.5.8.1) A number of commercial processes use the BINAP ligand, which has axial chirality. The PNNP ligand, on the other hand, has its chirality centred on the a-phenethyl groups two atoms removed from the phosphorus atoms, which bind to the rhodium ion. Nevertheless, good enantio.selectivity is obtained with this catalyst in the synthesis of L-phenylalanine. 

The preparation of BINAP reported in 1980 has marked a landmark in asymmetric catalysis and has illustrated the peculiar stereorecognitive properties inherent with the axially chiral 1,1 -binaphthalene framework. Since then, a great deal of work has been devoted to the preparation of binaphthalene-templated ligands of related design. These efforts have resulted in the... 

The use of an analogous (S)-BINAP-Ru-diacetate catalyst with axial chirality has led to important industrial applications, such as the synthesis developed by Monsanto where the asymmetric hydrogenation is involved in the last step to yield naproxen, a widely prescribed, non-steroidal, anti-inflammatory drug (Equation (9)).96... 

The hydrogenation of allylic alcohols and a,/>-unsaluraled acids leads to products with a very high synthetic potential, and both transformations were used quite early for industrial applications. In both cases Ru complexes with axially chiral biaryl ligands (binap analogues) are the catalysts of choice. Here, we will dis-... 

The palladium-catalyzed allene preparation method was extended to an asymmetric counterpart using a Pd/(R)-binap species as a chiral catalyst and axially chiral allenes 103 were obtained with good eantioselectivity [96]. It was found that the pres-... 

The axially chiral (allenylmethyl) silanes 110 were also prepared in optically active form using chiral Pd catalysts [98]. For the asymmetric synthesis of 110, a Pd/(R)-segphos system was much better in terms of enantioselectivity than the Pd/(R)-binap catalyst. Under the optimized conditions, 110m and llOt were obtained in 79% ee (57% yield) and 87% ee (63% yield), respectively (Scheme 3.56). The enantio-merically enriched (allenylmethyl) silanes 110 served for Lewis acid-promoted SE reaction with tBuCH(OMe)2 to give conjugated dienes 111 with a newly formed chiral carbon center (Scheme 3.56). During the SE reaction, the allenic axial chirality was transferred to the carbon central chirality with up to 88% transfer efficiency. 

DIOP contains two sp3 asymmetric carbons. DIPAMP possesses two asymmetric phosphorus atoms. The fully aromatic BINAP ligand possesses only axial chirality (13, 14). Although many phosphine ligands have only P-C bonds, some promising ligands possess P-O or P-N bonds (75). 

Benzamido-cinnamic acid, 20, 38, 353 Benzofuran polymerization, 181 Benzoin condensation, 326 Benzomorphans, 37 Benzycinchoninium bromide, 334 Benzycinchoninium chloride, 334, 338 Bifiinctional catalysts, 328 Bifiinctional ketones, enantioselectivity, 66 BINAP allylation, 194 allylic alcohols, 46 axial chirality, 18 complex catalysts, 47 cyclic substrates, 115, 117 double hydrogenation, 72 Heck reaction, 191 hydrogen incorporation, 51 hydrogen shift, 100 hydrogenation, 18, 28, 57, 309 hydrosilylation, 126 inclusion complexes, oxides, 97 ligands, 19, 105 molecular structure, 50, 115 mono- and bis-complexes, 106 NMR spectra, 105 olefin isomerization, 96... 

Besides BINAP or p-TolBINAP, optically active peraryldiphosphines with axial chirality based on the biphenyl groups (6,6 -dimethylbiphenyl-2,2 -diyl)bis(diphenylphosphine) and its analog are also effective ligands for the asymmetric isomerization as expected [21],... 

O) to give a hydroxylamino alcohol, Ph-N(OH)- CH(Me)CH2OH, using an axially chiral BINAP secondary amine catalyst in THF at 0 °C, followed by methanolic treatment with sodium borohydride.261 Yields up to 90% and ees up to 99% were recorded, and one-pot conversions to the corresponding /3-amino alcohol or /3-diamine are described. 

The BINAP ligand, 78, which is often used in asymmetric catalysis, possesses axial chirality in the binapthyl ring system as opposed to an asymmetrically substituted carbon atoms. They are made from chiral precursors using a nickel-catalysed coupling as the key step.23... 

Hoveyda clearly based his 1,1 -binaphthyl derived functionalised carbene not on BINAP, the phosphane, but on BINOL, the diol. By exchanging one hydroxy group with a carbene moiety, he arrived at a ligand system that provides axial chirality, a rigid metallacycle with chelate effect, and an anionic anchor point [6,78] (see Figure 5.20). 

A further highlight was introduced by R. Noyori in the 1980s when an efficient stereoselective hydrogen migration (allylamine —> enamine) was found to occur with Rh catalysts containing the BINAP diphosphine ligand of axial chirality (see Scheme 3 and Section 2.9). An L-menthol synthesis with an annual production of 2000 tons was the first commercial result of this development at Takasago Perfumery Co. Ltd. in Japan [66]. 

T7.11 BINAP (short for 2,2 -bis(diphenylphosphino)-l,r-binaphthyl) has axial chirality with the chiral axis coinciding with the C-C bond connecting two naphthyl systems. The bulky diphenylohosphino groups as well as indicated H atoms on naphthyl groups prevent the rotation around this C-C bond making the structure stable with respect to racemisation ... 

The first place in catalytic hydrogenation nowadays is taken by Rh or Ru complexes of BINAP. This ligand has axial chirality as the naphthalene rings cannot rotate past each other. These compounds were developed by Noyori, who with Knowles and Sharpless received the 2001 Nobel prize for their contributions to asymmetric synthesis. BINAP 20 is usually made from BINOL 19 and either 19 or 20 can be resolved. Rhodium complexes similar to those we have met include a molecule of cyclooctadiene and, as these are Rh(I) compounds, a counterion, often triflate 21. Both enantiomers of BINAP are available commercially.8... 

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