BINOL preparation

Secondary butyl alcohol, methylethyl car-binol, 2-butanol, CH3CH2CH(Me)OH. B.p. I00°C. Manufactured from the butane-butene fraction of the gas from the cracking of petroleum. Used to prepare butanone. 

Polymer-supported BINOLs thus prepared were treated with Zr(Ot-Bu)4 to form polymer-supported zirconium 20. In the presence of 20 mol% of various zirconium 20, the model aza Diels-Alder reactions of imine Id with Danishefsky s diene (7a) were performed results from selected examples are shown in Table 5.8. Whereas the 4-t-butylphenyl group resulted in lower enantiomeric excess (ee), higher ee were obtained when 3,5-xylyl, 4-biphenyl, 4-fluorophenyl, and 3-tri-... 

More recently, the same group has used a simpler and more easily prepared chiral ammonium phase-transfer catalyst 99 derived from BINOL in asymmetric Darzens reactions with a-halo amides 97 to generate glycidic tertiary amides 98 (Table 1.13). Unfortunately the selectivities were only moderate to low [48]. As mentioned in Section 1.2.3.1, tertiary amides can be converted to ketones. 

The reaction between epoxides and ammonia is a general and useful method for the preparation of P-hydroxyamines. " Ammonia gives largely the primary amine, but also some secondary and tertiary amines. The useful solvents, the ethanolamines, are prepared by this reaction. For another way of accomplishing this conversion, see 10-54. The reaction can be catalyzed with Yb(OTf)3 and in the presence of a-BINOL is l,l -bi-2-naphthol derivative gives amino alcohols with high asymmetric induction. A variation used Yb(OTf)3 at lOkbar or at ambient pressure. Lithium triflate can also be used. Primary and secondary amines give, respectively, secondary and tertiary amines, for example. 

The stereoselective synthesis of hexacoordinated phosphate anions was also reported by the same group. A general one-pot process was developed for the preparation of C2-symmetric anions 15,16 and 17 containing enantiopure BINOL, hydrobenzoin, and tartrate-derived ligands respectively [38-40] Cpsymmetric anion 18 being prepared similarly in two steps from methyl-a-... 

Closely related transformations were also catalyzed by the in situ prepared lan-thanum-lithium-BINOL (LLB) catalyst developed by Shibasaki (Scheme 5-28). 

An improved preparation of Shibasaki s LLB catalyst allowed higher asymmetric induction in the chemistry shown in Scheme 5-28. The new recipe involved mixing LaCl3 7H20 (1 equiv.), BINOL-dilithium salt (2.7 equiv.) and NaOt-Bu (0.3 equiv.) in THF at 50°C. This catalyst allowed asymmetric hydrophosphonylation of aldehydes in high yields and up to 95% ee (Scheme 5-33, Eq. 1), and gave better results for aliphatic aldehydes than a related aluminum catalyst (ALB, see Scheme 5-37 below). 

Several catalysts based on Ti(IV) and BINOL have shown excellent enantiose-lectivity in Mukaiyama aldol reactions.156 A catalyst prepared from a 1 1 mixture of BINOL and Ti(0-i-Pr)4 gives good results with silyl thioketene acetals in ether, but is very solvent sensitive.157... 

Allylstannane additions to aldehydes can be made enantioselective by use of chiral catalysts. A catalyst prepared from the chiral binaphthols R- or S-BINOL and Ti(0-i-Pr)4 achieves 85-95% enantioselectivity.187... 

Metljylcoumarone has been prepared by the cyclization of ethyl a-phenoxyacetoacetate followed by hydrolysis and decarboxylation of the resulting ethyl 3-methylcoumarilate,3 4 by debromination and rearrangement of 3,4-dibromo-4-methyl-coumarin to 3-methylcoumarilic acid followed by decarboxylation,4-6 by cyclization of phenoxyacetone with concentrated sulfuric acid,6 and by treatment of 3-coumaranone with methyl-magnesium iodide followed by dehydration of the resulting car-binol.7... 

Over the last few years several examples have been reported in the field of asymmetric catalysis that are based on the interaction of two centers.6,119 Recently, Shibasaki and coworkers have developed an asymmetric two-center catalyst. Scheme 3.14 shows preparation of optically active La binaphthol (BINOL). This catalyst is effective in inducing the asymmetric nitro-aldol reaction, as shown in Scheme 3.15. 

Scheme 3.14. Preparation of the optically active La-BINOL complex...

Enantioselective Diels-Alder reactions proceed smoothly in the presence of a chiral Sc catalyst, prepared in situ from Sc(OTf)3, R)- I )-l,l -bi-2-napluhol [(R)-BINOL], and a tertiary amine in dichloromethane.58 The catalyst is also effective in Diels-Alder reactions of an acrylic acid derivative with dienes (Scheme 14). 

Preparation of diethyl (S)-a-hydroxybenzylphosphonate — Reaction of an aldehyde with a dialkyl phosphite facilitated by a chiral BINOL complex... 

Two reports have been made of the preparation of P-chiral phosphine oxides through reaction of chiral f-butylphenylphosphine oxide treated with LDA and electrophiles. The electrophiles included aldehydes,355 ketones,355 and benzylic-type halides.356 Optically active a-hydroxyphosphonate products have also been generated from aldehydes and dialkyl phosphites using an asymmetric induction approach with LiAl-BINOL.357... 

Ligand 73 was prepared directly from a single enantiomer of the corresponding naphthol of QUINAP 60, an early intermediate in the original synthesis, and both enantiomers of BINOL. Application in hydroboration found that, in practice, only one of the cationic rhodium complexes of the diastereomeric pair proved effective, (aA, A)-73. While (aA, A)-73 gave 68% ee for the hydroboration of styrene (70% yield), the diastereomer (aA, R)-73 afforded the product alcohol after oxidation with an attenuated 2% ee (55% yield) and the same trend was apparent in the hydroboration of electron-poor vinylarenes. Indeed, even with (aA, A)-73, the asymmetries induced were very modest (31-51% ee). The hydroboration pre-catalyst was examined in the presence of catecholborane 1 at low temperatures and binuclear reactive intermediates were identified. However, when similar experiments were conducted with QUINAP 60, no intermediates of the same structural type were found.100... 

In 1993, we reported that various unsaturated heterocycles can be alkylated with Et-, wPr- and nBuMgCl in the presence of optically pure (EBTHI)ZrCl2 (3a) or (EBTHI)Zr-binol (3b) to afford the derived unsaturated products in >90% ee (cf. 5 6, Scheme 2) [4a]. Many of the simpler five- and six-membered starting materials are available commercially or can be prepared by established procedures. In contrast, catalytic enantioselective reactions involving unsaturated medium ring hetero cycles were not a trivial undertaking the synthesis of these olefinic substrates, by the extant methods, was prohibitively cumbersome. 

It thus came as a surprise that in the year 2000, three groups independently reported the use of three new classes of monodentate ligands (Scheme 28.2) [12], The ligands induced remarkably high enantioselectivities, comparable to those obtained using the best bidentate phosphines, in the rhodium-catalyzed enantioselective alkene hydrogenation. All three being based on a BINOL backbone, and devoid of chirality on phosphorus, these monophosphonites [13], monophosphites [14] and monophosphoramidites [15] are very easy to prepare and are equipped with a variable alkyl, alkoxy, or amine functionality, respectively. 

The use of monodentate phosphoramidites in enantioselective hydrogenation was first reported in 2000, together with reports on the use of phosphites and phospho-nites [15]. Phosphoramidites are prepared in a variety of ways, but the most common route is the treatment of a diol with PC13, followed by addition of an amine [60, 61]. MonoPhos (29a), the first reported phosphoramidite used as a ligand, is prepared from BINOL and HMPT in toluene [62]. Phosphoramidites, especially... 

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