Chiral BINAPO

A novel procedure for the synthesis of an indole skeleton 81 was developed by Mori s group (Scheme 13).16e,16f Enantioselective allylic amination of 78 with A-sulfonated < r/ < -bromoaniline 79 followed by Heck cyclization of 80 provided chiral indoline 81. The treatment of a cyclohexenol derivative 78 with 79 in the presence of Pd2(dba)3-GHGl3 and ( )-BINAPO gave compound 80 with 84% ee in 75% yield. Total syntheses of (—)-tubifoline, (—)-dehydrotubifoline, and (—)-strychnine were achieved from compound 80. 

Tokuoka, E. Kotani, S. Matsimaga, H. Ishizuka, T. Hashimoto, S. Nakajima, M. (2005) Asymmetric ring opening of meso-epoxides catalyzed by the chiral phosphine oxide BINAPO., Tetrahedron Asymmetry 16 2391-2392. 

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. 

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... 

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. 

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. 

A large group of catalysts performed well in the opening of derivatives of ds-stilbene oxide 21.131 (R = Ar). A high level of enantioselectivity was attained with the axially chiral phosphoramide 21.140, BINAPO 21.14, ... 

A clearly innovative catalytic system was reported by Nakajima and co-workers [48], who introduced chiral phosphine oxides as suitable Lewis bases for activating trichlorosilane in stereoselective transformations. Indeed trichlorosilane has been used in the conjugate reduction of a,p-unsaturated ketones in the presence of a catalytic amount of a chiral Lewis base. The reduction of 1,3-diphenylbutenone promoted by catalytic amounts of 2,2 -bis(diphenylphosphanyl)-l,l -binaphthyl dioxide (Cat. 15, BINAPO) at 0°C led to the corresponding saturated compound in 97% yield and a somehow surprising, but very good, 97% ee (Scheme 15.19). 

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)... 

The success of stereoselective reactions involving both phosphate, phosphonate and phosphinic derivatives relied on application of binaphthyl moieties, like in chiral BINOL derivatives 26-30, phosphine oxide (S)-BINAPO and derivatives 109, 111, 137. 

It has been also found that chiral phosphine oxides (5)-BINAPO catalyzed silicon tetrachloride-mediated, enantioselective phosphonylation of aldehydes with trialkyl phosphites, led to formation of optically active a-hydroxyphosphonates with low to moderate enantioselectivities (ee 22-52%)7 This reaction constituted the first example of asymmetric Abra-mov-type phosphonylation of aldehydes with trialkyl phosphites catalyzed by chiral Lewis bases. 

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... 

After Kobayashi spioneering study on theabiUty of (S)-2,2 -bis(diphenylphosphanyl)-1,1 -binaphthyl dioxide (9, BINAPO) as a promoter of the enantioselective allylation of a-hydrazono esters with allyltrichlorosilanes [27], Nakajima reported the first catalytic system for the allylation of aldehydes, in which the use of N,N-diisopropylethylamine and tetrabutylammonium iodide was essential for accelerating the catalytic cycle (Scheme 7.16) [28], For this allylation, y-functionahzed nucleophiles such as cis-y-bromoallyltrichlorosilane could be employed as addressed by Maikov and Kodovsky [29], In addition, 9 could be apphed to the asymmetric ring opening of meso-epoxides with SiCh, as expected from the scope of the chiral bipyridine N,N -dioxide catalysis [30], and could also catalyze the SiCfi-mediated, enanhoselective phosphonylation of aldehydes with trialkyl phosphites [31],... 

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. 

Cross aldehyde reaction between simple ketones has been promoted enantioselectively by chiral l,T-binaphthyl 2,2 -(POPh2) (BINAPO), with SiCl30Tf/i-Pr2NEt. ... 

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