1,1 -binaphthyl dimer

An enantiopure dimer 149 with a l,l -binaphthyl-bridge was prepared via the bis-tosylhydrazone (see Table 4.4, page 130/131) [122], The electronic properties of these dimers, such as the electronic absorphon spectra and cyclic voltammetry, are indistinguishable from those of other methano-bridged fullerenes. CV-data show clearly that the two CgQ-imits of the binaphthyl-dimer are reduced independently [122],... 

In search of a convenient procedure for preparing diazo substrates for the cycloaddition to Cgg, Wudl introduced the base-induced decomposition of tosyl-hydrazones [116]. This procedure allows the in situ generation of the diazo compoimd without the requirement of its purification prior to addition to Cgg. Since they are rapidly trapped by the fullerene, even unstable diazo compounds can be successfully used in the 1,3-dipolar cycloaddition. In a one-pot reaction the tosyUiydrazone is converted into its anion with bases such as sodium methoxide or butylHfhium, which after decomposition readily adds to Cgg (at about 70 °C). This method was first proven to be successful with substrate 142. Some more reactions that indicate the versatility of this procedure are shown in Table 4.4. Reaction of 142 with CgQ under the previously described conditions and subsequent deprotection of the tert-butyl ester leads to [6,6]-phenyl-C5j-butyric acid (PCBA) that can easily be functionalized by esterification or amide-formation [116]. PCBA was used to obtain the already described binaphthyl-dimer (obtained from 149 by twofold addition) in a DCC-coupling reaction [122]. 

L. Pu, l,l -Binaphthyl Dimers, Oligomers and Polymers Molecular Recognition, Asymmetric Catalysis and New Materials, Chem. Rev. 1998, 98, 2405-2494. 

Pu L (1998) 1, l -binaphthyl dimers, oligomers, and polymers molecular recongition, asymmetric catalysis, and new materials. Chem Rev 98 2405-2494... 

Rajca and coworkers have elaborated on the core structure of the cycUc ortho-tetraphenylene via the synthesis of a helical l,l -binaphthyl dimer as outlined in Scheme 6.19 [51]. This work represents the first example of a non-racemic macrocycle provided in this discussion. (R)-2,2 -Dibromo-l,l -binaphthyl 123 was fully lithiated and subsequently oxidatively coupled using CuBr2 to form the double helical 124 in >95% ee. The authors noted that similar reactions performed with racemic 123 led to complex mixtures of products and low isolated yields of the desired cyclic species 124. 

Scheme 6.19. Synthesis and solid-state structure of helical binaphthyl dimer 124 (inset). Reagents and conditions (a) BuLi, -35 °C, EtjO, then CuBr2, -78 °C.

The use of chiral C2-symmetric trifluoromethanesulfonamides derived from (i )-1,1 -binaphthyl-2,2 -diamine in similar reactions to those described above has led to the formation of the expected alcohols with enantioselectivities of 43-54% ees. Better enantioselectivities were observed by Paquette et al, resulting from the use of chiral C2-symmetric VERDI (verbenone dimers) disulfonamides derived from the dimerisation of (+ )-verbenone. Stereoselectivity levels ranging from 72 to 98% ee were observed, depending on the structural characteristics of the aldehyde (Scheme 3.45). ... 

Tanaka et al. (1996,2000) studied the behavior of a series of naphthalene derivatives in AN solution containing NaN02 and CF3SO3H at 0°C in air. Naphthalene showed very low reactivity, and most of the starting material was recovered after the reaction. In case of 1-methylnaphthalene, a coupling reaction took place to produce 4,4 -dimethyl-l,T-binaphthyl in 91% yield alongside mononitro derivatives of the dimer in 1.5% yield. However, when the reaction is carried out on the same conditions but in inert (Nj) atmosphere, the yield of the dimer decreased from 97 to 15%, and no mononitro derivatives were formed. Therefore, the oxidation of NO with O2 to form NO2 (after the electron transfer to NO from 1-methylnaphthalene) is an obvious step of the reaction depicted in Scheme 4.42. 

In terms of nitration, the system (NaN02 + CF3SO3H) is of no interest. At the same time, dimerization in this system can be attractive. For the last direction, CF3SO3H (or FSO3H) is necessary to produce binaphthyl derivatives more preferentially than nitro compounds (Tanaka et al. 1996). This work was preceded by the observation that the reaction of NO+AICI4 with 1-methyl-, 1,2-dimethyl-, 1,3-dimethyl, or 1,8-dimethylnaphthalenes in liquid SO2 leads to a partial a,a-dimerization (see Borodkin et al. 1993). Ozeryanskii et al. (1998) published the dimerization of l,8-Af,Af-bis(d imethylamino)naphthalene by the action of NOj in CHCI3. This reaction is accompanied by the formation of 4-nitro-l,8-A,A-bis(dimethylamino)naphthalene. Both gronps of anthors consider cation-radicals of the initial substrates as intermediate species. 

From product analysis, fluorescence quenching, and LFP, initially formed trinaphthyl phosphates (9" ) and dinaphthyl methylphosphonates (10 ) decompose into 1,1 -binaphthyl (Np2) and 1-naphthyl phosphate or methyl phosphate, respectively. Although it is suggested that 9 and 10" change to the intramolecular ir-dimer between two Np... 

The oxidation of phenols forming aryloxyl radicals was first recognized by Pummerer and Frankfurter in 1914," who reacted 2,2 -dihydroxy-l,l -binaphthyl with ferricyanide, and isolated dimers and trimers of the radical 20 (equation 8), which was later observed by ESR." Many further examples were studied by Goldschmidt, Muller, and others," and an X-ray crystal structure confirmed dimer formation with C—O bonding at the 4-position for 3-bromo-2,4,6-triphenylphenoxyl. ... 

The formation of dimers was also observed - in the electrolysis of RMgBr solutions in EtaO with R = a-Naph (the yield of l,l -binaphthyl was 43%) and a number of Grignard reagents with R being the derivatives of terpenes. 

The tautomer 82c of 3-methylimidazole, however, was found in the 1 1 complex with rac-17. X-ray structure analysis of the above inclusion complex showed that molecules of 82c act as hydrogen-bond donors and acceptors between two dimeric assemblies of binaphthyl molecules (Scheme 2). Methyl groups are located in the vicinity of the dimeric host. However, steric hindrance of this methyl group is less important for the energetics of crystal construction than formation of two hydrogen bonds. 

Stereoselective synthesis of perylenequinones. Synthesis of the symmetrical perylenequinone phleichrome (4) has been effected by coupling of two identical naphthalene units to provide a binaphthol, which is then oxidized to a perylenequinone. Thus the bromonaphthalene 1 on halo-lithium exchange (f-BuLi) followed by reaction of anhydrous FeCl3 dimerizes to two optically active binaphthyls, (+)-and (— )-2, with 3 1 diastereoselectivity. 

The most frequently applied ligands are 2,2 -binaphthol (BINOL la) and 2,2 -bis(diphenyl-phosphino)binaphthyl (BINAP lb). Both antipodes of these compounds are commercially available in enantiopure form, though not at little cost [3]. It is rewarding, therefore, to become acquainted with the syntheses of these compounds, which have been described in detail [4J and have been simplified substantially on the basis of recent publications [5J. The iron(lIl)-catalyzed dimerization of 2-naphthol (2) to give racemic BINOL (rac)-la succeeds smoothly and on a large scale (Scheme 1). Its resolution can be achieved easily with N-benzylcinchoidinium chloride (3) and yields both (/ )- and (5 )-la in high enantiomeric excesses. After conversion into the ditri-flate 4, enantiopure la can be coupled with diphe-nylphosphine (or, in lower yield, with cheaper chlorodiphenylphosphine) in a nickel-catalyzed... 

The effects of the role of matrix birefringence, photoselection, and rotational diffusion on measuring the circular dichroism of chiral excited triplets embedded in a rigid matrix have been examined. The techniques described in this paper are applied to chiral dimer-like molecules in the binaphthyl and spirobifluorene series. Natural and magnetic circular dichroism spectra of selenofenchone provide evidence for a singlet-triplet component of the n - IT transition. ... 

In addition to this enhancement, several other effects can be induced by the new conformation at the microscopic scale, such as the appearance of olf-diagonal molecular hyperpolarizability tensor components. The study of these microscopically aligned molecules has also provided new fundamental insights and was only made possible through creative synthetic chemistry. The systems that have been studied so far include dimers and tetramers such as the binaphthyl ethers and the calixarenes, and polymers with rigid backbones that force the pendant D ti-A chromophores into a non-centrosymmetric conformation. 

The dimeric l,l -binaphthyl-2,2 -diamine-derived phosphoramide 81 effectively catalyzes the asymmetric process, occasionally with high stereoselectivity. The adducts, / -hydroxyaldehydes, can be isolated as the stable dimethyl acetals by treatment of the reaction mixture with MeOH. 

Although the classical Wurtz-Fittig synthesis has been widely replaced by procedures using milder reaction conditions (see following chapters), alkali metals like potassium in dimethoxyethane (DME) have been used in the dimerization of 1,1 binaphthyls (e.g. 47, see Scheme 21) to perylene derivatives (e.g. 

Binaphthyls. Naphthalene derivatives undergo oxidative dimerization on treatment with NaNOj and triflic acid in MeCN. Radical cation intermediates are involved. 

---