Ligands BINAPO

New inq)etus for asymmetric hydroformylations came primarily from Takayas phosphine-phosphinite ligand (BINAPO) 4 which constitutes an enormous breakthrough l In combination with rhodium the BINAPO ligand gave enantioselectivities up to 95% and i/n ratios > 86/14 in the hydroformylation of substituted styrene derivatives. Conversions are > 99% at substrate/catalyst ratios between 300 and 2000. Shortly afterwards, similar catalytic results were reported by Union Carbide with chiral diphosphinite ligands, e.g. 5 . After many years of stagnation these new catalysts now point the way towards fixture developments in asymmetric hydroformylation. 

The chiral ligand BINAP was originally prepared from 2,2 -binaphthol and resolved by complexation with an optically active Pd complex [ 10]. A new method starting from 2-naphthol was developed (Scheme 3.2) [11], In this method optical resolution was achieved at the stage of BINAP dioxide (BINAPO) by using inexpensive optically active acids such as camphorsul-fonic acid and dibenzoyltartaric acid. 

With BINAPO as ligand, the alkylation of dibenzoate 92 with p-ketoester 101 provides the mono-alkylated product 102 in modest ee (Scheme 8E.13) [65], Subsequently, a simultaneous allylation-Heck annulation reaction provided the pentacycle 103, which was further function-... 

Desymmetrization of a seven-membered cyclic meso compound, followed by a metallo-ene reaction, provides ready access to the trans-hydroazulene skeleton (Scheme 8E.15) [69]. By using BINAP in preference to BINAPO ligand, which gave a lower enantioselectivity (70% ee), two alkylation products were obtained in differential enantioselectivities. The high enantiopurity of the major product 106 may be the consequence of a subsequent kinetic resolution because the second ionization, followed by proton loss from enf-106, involved a matched event. 

In one of the few examples of a chiral ligand-controlled asymmetric reaction mediated by Sml2, Mikami reported the use of the chiral, bis-phosphine oxide, BINAPO (4), as a Lewis basic additive.23 For example, reductive coupling of methyl acrylate and acetophenone using Sml2 in THF with 2 equiv of BINAPO gave lactone 5 in 46% yield and 67% ee (Scheme 2.8).23... 

Chan and coworkers applied catalysts based on (R) P Phos (16, Table 6.4, entries 3 and 4) [118], BINAPO (17 and 18, entries 5 and 6) [119], and atropisomeric (13, entry 7) [ 120] ligands to the reaction. Ligand 16 was particularly interesting because its polar nature allowed the catalyst to be immobilized and recycled. After using [Ir(COD)Cl[2/ I6/I2 to catalyze the hydrogenation of 2 methylquinoline in biphasic mixtures of hexane and dimethyl poly (ethylene glycol) (dmpeg), the authors decanted off the... 

Mori et al. have shown that asymmetric alkylation with an allylic tosyl amide followed by a zirconium-promoted cyclization provides an efficient route to mesembrine and mesembrane alkaloids [107]. The best ee was obtained with BINAPO as the ligand. Scheme 28. The product was obtained in 86% ee and following recrystallization the sulfonamide was obtained in 99% ee. 

A single attempt has been made to induce asymmetry in the intermolecular cross coupling reaction by employing a chiral ligand for the samarium ketyl [56]. Utilizing 2,2 -bis(diphenylphosphinyl)-l,l -binaphthyl (BINAPO) as a chiral ligand, a modest start has been made to develop an enantioselective process. However, in the examples reported to date the method is plagued by low yields and/or moderate stereoselectivities. 

Recently, enantioselective additions of samarium diiodide-generated ketyl radicals to olefins have been demonstrated [15]. As illustrated in Eq. (10), the reductive coupling of acetophenone with methyl acrylate (31a) in the presence of chiral phosphine ligand 29 (i -BINAPO) gives somewhat low yields (mostly under 50%) but moderate to good levels of enantioselectivity (60-70% ee) for the y-butyrolactone products 34. 

Efficient asymmetric hydrosilylation of 1-alkenes and selected terminal olefins proceeding in the presence of palladium complexes, such as [ PdCK ) -CsH5) 2], combined with axially chiral monodentate phosphine ligands (MOPs) (Fig. 8) was reported in 1991 by Hayashi and Uozumi (190). [Pd]/MOP systems are highly active and regio- and enantioselective in the asymmetric hydrosilylation of 1-alkenes, terminal olefins (especially styrenes), and cycloolefins with trichlorosilane. Asymmetric hydrosilylation of styrenes occurs successfully in the presence [ PdCl( f-C3H5) 2] combined with MOP (Fig. 8a) (ee up to 94%), modified MOP (Fig. 9) (ee up to 98%), (S)-BINAPO (ee up to 72%), BINASb (Fig. 8b)... 

Synthesis of MOP ligands from the BINAPO-borane complex by phosphine oxide/metal... 

Leung et al. described titanium(rv) terminal hydroxo complexes containing chelating bis(phosphine oxide) ligands, such as BINAPO. The metal ion extracting ability of mainly a-keto-phosphine oxides and related compounds (Fig. 4) based on complex formation has been investigated by quantum chemical calculations. ... 

In the first chapter, key chiral intermediate 39 was obtained at 40 % e.e. by catalytic allylic alkylation of 38 promoted by the palladium complex of (5 -BINAPO, ligand... 

Zhou Y-G, Tang W, Wang W-B, Li W, Zhang X. Highly effective chiral ortho-substituted BINAPO ligands (o-BINAPO) applications in Ru-catalyzed asymmetric hydrogenations of p-aryl-substituted p-(acylamino)acrylates and P-keto esters. J. Am. Chem. Soc. 2002 124(18) 4952-4953. 

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