Synthesis BINOL-derived

Soon thereafter, the Yamamoto group reported an extension of this work to the highly diastereo- and enantioselective synthesis of nitroso Diels-Alder-type bicycloketones using dienamines in the presence of the BINOL derivative 44 (Scheme 5.61) [115]. This reaction was thought to proceed through a sequential N-NA/ hetero-Michael reaction mechanism. Support for this mechanism was provided from an experiment employing bulkyl 4,4-diphenyl dienamine where the N-NA... 

M. Shi and Y.-L. Shi reported the synthesis and application of new bifunctional axially chiral (thio) urea-phosphine organocatalysts in the asymmetric aza-Morita-Baylis-Hillman (MBH) reaction [176, 177] of N-sulfonated imines with methyl vinyl ketone (MVK), phenyl vinyl ketone (PVK), ethyl vinyl ketone (EVK) or acrolein [316]. The design of the catalyst structure is based on axially chiral BINOL-derived phosphines [317, 318] that have already been successfully utilized as bifunctional catalysts in asymmetric aza-MBH reactions. The formal replacement of the hydrogen-bonding phenol group with a (thio)urea functionality led to catalysts 166-168 (Figure 6.51). 

The authors also investigated the mode of activation of these BINOL-derived catalysts. They proposed an oligomeric structure, in which one Ln-BINOL moiety acts as a Brpnsted base, that deprotonates the hydroperoxide and the other moiety acts as Lewis acid, which activates the enone and controls its orientation towards the oxidant . This model explains the observed chiral amplification effect, that is the ee of the epoxide product exceeds the ee of the catalyst. The stereoselective synthesis of cw-epoxyketones from acyclic cw-enones is difficult due to the tendency of the cw-enones to isomerize to the more stable fraw5-derivatives during the oxidation. In 1998, Shibasaki and coworkers reported that the ytterbium-(f )-3-hydroxymethyl-BINOL system also showed catalytic activity for the oxidation of aliphatic (Z)-enones 129 to cw-epoxides 130 with good yields... 

BINOL and its derivatives have been utilized as versatile chiral sources for asymmetric catalysis, and efficient catalysts for their syntheses are, ultimately, required in many chemical fields [39-42]. The oxidative coupling of 2-naphthols is a direct synthesis of BINOL derivatives [43, 44], and some transition metals such as copper [45, 46], iron [46, 47] and manganese [48] are known as active metals for the reaction. However, few studies on homogeneous metal complexes have been reported for the asymmetric coupling of 2-naphthols [49-56]. The chiral self-dimerized V dimers on Si02 is the first heterogeneous catalyst for the asymmetric oxidative coupling of 2-naphthol. 

Diols such as the optically active 1,1 -binaphthyl-2-2 -diol (BINOL) have been used as versatile templates and chiral auxiliaries in catalysts employed successfully in asymmetric synthesis. The application of enzymes in the enantioselective access to axially dissymmetric compounds was first reported by Fujimoto and coworkers.83 In aqueous media, the asymmetric hydrolysis of the racemic binaphthyl dibutyrate (the ester) using whole cells from bacteria species afforded the (A)-diol with 96%ee and the unreacted substrate (A)-ester with 94% ee at 50 % conversion. Recently, in non-aqueous media, lipases from Pseudomonas cepacia and Ps. fluorescens have been employed in the enantioselective resolution and desymmetrization of racemic 6,6 -disubstituted BINOL derivatives using vinyl acetate.84 The monoacetate (K)-73 (product) was obtained in 32-44 % chemical yields and 78-96% ee depending on the derivatives used. The unreacted BINOL (S)-72 was obtained in 30-52 % chemical yield and 55-80% ee. 

A BINOL-derived phosphoric acid derivative has been used as a catalyst in the enantioselective synthesis of a-amino phosphonates via hydrophosphonylation of imines with diisopropyl phosphite.82... 

Recently, Reek et al. published the synthesis of a 9H,9 H- [4,4 ]bicarbazole-3,3r-diol (BICOL)-based chiral monodentate phosphoramidite ligand, which was functionalized with two different third-generation carbosilane dendritic wedges (Fig. 26) [57]. As reference reaction in the catalytic study, the rhodium-catalyzed asymmetric hydrogenation of Z-methyl-a-acetamido-cinnamate was chosen. Using a ligand-to-rhodium ratio of 2.2 led to enantio-selectivities which were comparable to the results obtained using the parent BINOL-derived monodentate phosphoramidite MonoPhos. 

In the reaction of 1-naphthoxide ions, a mixture of 2- and 4-aryl-, along with 2,4-diaryl-l-naphthol, is formed. However, substitution occurs only at C4 with the 2-Me-substituted anion (50-70% yields) [1[. On the other hand, 2-naphthoxide ions react with ArX to give substitution only at Cj of the naphthalene ring [32, 33]. The reactivity of the 2-naphthoxide ions allows the synthesis of naphthylpyridines, naphthylquinolines, and naphthylisoquinolines via their coupling reactions with the corresponding halo arenes, in good to excellent yields (50-95%) [33], The photostimulated reaction between 2-naphthoxide ions and l-iodo-2-methoxy-naphthalene was explored in liquid ammonia, as a novel approach to the synthesis of [1,1 ] binaphthalenyl-2,2 -diol (BINOL) derivatives (Scheme 10.23). This procedure has also been applied to the synthesis of BINOL in moderate yield (40%), which represents the first report of an SRN1 reaction in water [34]. 

A bidirectional benzannulation strategy allows the extension of an existing biaryl skeleton. The BINOL-derived bis-carbene complex 69, accessible through a sequence of regioselective double ortfio-lithiation/Fischer carbene complex synthesis, undergoes bidirectional benzannulation to give the dinuclear biphenanthrene complex 70. The optical induction exerted by the binaphthyl core is, however, only moderate a mixture of C2- and Cj-symmetrical bis(phenanthrohydroquinone) bis-chromium complexes is formed, in which the C2-... 

A series of dibenzofuran-l,4-diones illustrated in the following scheme were constructed via a DDQ-mediated intramolecular oxidative cyclization of quinone-arenols <070L2807>. Dibenzo[b] furans were also found to be made from 2//-pyran-2-ones and 6,7-dihydro-577-benzo[Z>]furan-4-one <07T1610>. The asymmetric synthesis of chiral furo-fused BINOL derivatives was achieved via copper(II)-mediated oxidative coupling from naphthofuranol in the presence of chiral phenylethylamine <07TL317>. 

Crown Ethers. BINOL-derived crown ethers have been reported. Crown ethers containing 3,3 -disubstituted BINOL derivatives are particularly effective for asymmetric synthesis. Thus complexes of these crown ethers (e.g. 18-Crown-6) with Potassium Amide or Potassium t-Butoxide catalyze asym-... 

Mukaiyama Aldol Condensation. As expected, the chiral titanium complex is also effective for a variety of carbon-carbon bond forming processes such as the aldol and the Diels-Alder reactions. The aldol process constitutes one of the most fundamental bond constructions in organic synthesis. Therefore the development of chiral catalysts that promote asymmetic aldol reactions in a highly stereocontrolled and truly catalytic fashion has attracted much attention, for which the silyl enol ethers of ketones or esters have been used as a storable enolate component (Mukaiyama aldol condensation). The BINOL-derived titanium complex BINOL-TiCl2 can be used as an efficient catalyst for the Mukaiyama-ty pe aldol reaction of not only ketone si ly 1 enol ethers but also ester silyl enol ethers with control of absolute and relative stereochemistry (eq 11). ... 

Diels-Alder Reaction. The Diels-Alder reaction of methacrolein with 1,3-dienol derivatives can also be catalyzed by the chiral BINOL-derived titanium complex BINOL-T1CI2. The endo adduct was obtained in high enantioselectivity (eq 15). The sense of asymmetric induction is exactly the same as observed for the asymmetric catalytic reactions shown above. Asymmetric catalytic Diels-Alder reactions with naphthoquinone derivatives as a dienophile provide an efficient entry to the asymmetric synthesis of anthracyclinone aglycones (eq 16). ... 

Enantioselective Polyene Cyclization Catalyzed SnCU-BINOL Derivatives. Non-enzymatic enantioselective polyene cyclizations are very attractive alternatives to the multistep synthesis from naturally occurring chiral synthons. The authors have succeeded in the first enantioselective biomimetic cyclization of polyprenoids catalyzed by LBA. (—)-Ambrox is the most important commercial substitute for ambergris, due to its unique olfactory and fixative properties. The successful preparation of (—)-ambrox has been achieved by the enantioselective cyclization of homofamesol promoted by (/ )-BINOL-Me-SnCl4, although the enantioselectivity and diastereoselectivity is moderate (eq 10). 

The TADDOL-derived titanium catalyst has also been used for inverse electron-demand Diels-Alder reactions [124-127], although Posner favored the use of a BINOL-derived titanium catalyst in his inverse electron-demand Diels-Alder reactions for the synthesis of la,25(OH)2D3 (Sch. 47) [125,126]. 

In this chapter, we focus on recent achievements in the enantioselective synthesis of chiral amines using 1,1 bi 2 naphthol (BINOL) derived monophosphoric acid (1) or related phosphoric acids as chiral Bronsted acid catalysts 2, 3], The contents are arranged according to the type of bond forming reaction, including carbon carbon, carbon hydrogen, and carbon heteroatom bond forming reactions, followed by specific reaction types. 

Phosphorodithioic adds have been prepared according to an improved synthesis of 3,3 -disubstituted BINOL derivatives (226-231). In preliminary experiments, these new Bronsted adds were tested as organocatalysts in three reactions. They promoted the Nazarov cyclisation with mixed selec-tivities, the Mannich reaction with good enantioselectivity and they catalyzed efficiently the alkylation of iV-acyliminium with enol silyl ether. ... 

All of the above methods introduce the aryl group during the enantiodetermining step. An alternative strategy would be to already have the aryl group in place and to generate the tertiary stereocentre via an asymmetric protonation of an enolate complex. This was first reahsed by the pioneering work of Yamamoto in this area with the use of Lewis acid assisted chiral Bronsted acid (LBA) catalysts in the enantioselective synthesis of a-aryl cyclohexanones ((2), Scheme 4.34). Initially developed with the use of stoichiometric quantities of a BlNOL-SnCLi catalyst for the asymmetric protonation of silyl enol ethers, [63] the extensive development of this reaction has resulted in a catalytic variant with an achiral proton donor [64] and expansion of the scope to include tertiary a-aryl carboxylic acids. [65] Further improvement was made with the development of a metal free IV-triflyl thiophos-phoramide BINOL derived proton source (126) [66] and more recently a Lewis base-tolerant chiral LBA [67]. 

In 2005 Dixon and Tillman published an enantioselective methodology for the addition of methyleneaminopyrrolidine to imines catalysed by Bronsted acids (Scheme 24.17) in particular, a new series of synthetic multidentate BINOL derivatives proved to be catalytically effective in the synthesis of a-aminohydrazones. 

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