1.3- Diphenylethane-1,2-diol

The reaction of butyllithium with 1-naphthaldehyde cyclohexylimine in the presence of (/C )-l,2-diphenylethane-1,2-diol dimethyl ether in toluene at —78 °C, followed by treatment with acetate buffer, gave 2-butyl-1,2-dihydronaphthalene-l-carbaldehyde, which was then reduced with sodium borohydride in methanol to afford (1 R,2.S)-2-butyl-1 -hydroxymcthyl-1,2-dihydronaphthalene in 80% overall yield with 91 % ee83. Similarly, the enantioselective conjugate addition of organolithium reagents to several a,/J-unsaturated aldimines took place in the presence of C2-symmetric chiral diethers, such as (/, / )-1,2-butanediol dimethyl ether and (/, / )- ,2-diphenylethane-1,2-diol dimethyl ether. 

Dioxolanes derived from sy -l,2-diphenylethane-l,2-diol react with dienes such as cyclopentadiene and isoprene, but in most cases the diastereoselectivity is low. 

Fig. 10.28. The stereochemistry of enzymatic hydrolysis of stilbene oxide. The achiral (meso) r/.v-sli Ibene oxide (10.7) yields only one of the two enantiomers of IhreoA,2-diphcnylethane-1,2-diol (10.122). In contrast, the chiral trans-stilbene oxide (10.121) is hydrated exclusively to meso-l -diphenylethane-l -diol [182][183]. 

The chiral substrate trans- stilbene oxide (10.121) behaved differently, yielding meso-l,2-diphenylethane-l,2-diol (meso-10.122) [183], This means that, in both enantiomeric substrates, the enzyme does not discriminate between the two oxirane C-atoms, bringing about inversion of configuration at the C-atom attacked. Interestingly, the various stereoisomers of 1,2-diphenylethane-l, 2-diol can be interconverted metabolically by alcohol/ketone equilibria catalyzed by alcohol dehydrogenases. 

Treatment of benzaldehyde with TiCU (lequiv.) and magnesium (l.Sequiv.) in TFIE at 25°C for 30min gives a mixture of 1,2-diphenylethene (43% yield) and dl- and OT ro-l,2-diphenylethane-l,2-diols (29% combined yields, dljmeso = AZiS ). The reaction conducted at 80°C produces the diphenylethene in 62% yield selectively. However, when catechol (1 equiv.) is added to the reaction mixture, pinacols are produced selectively in 76% yield dljmeso = 54/46) even at 80 °C. " Ultrasonic irradiation of a mixture of TiCU (15% in dilute HCl solution, 2 equiv.) and magnesium (4 equiv.) in EtOH accelerates the pincaol formation, but the diastereomeric ratio remains at a low level (dljmeso = 68/32). ... 

Included in this class of olefins is ( )-stilbene (entry 20), which throughout studies of AD has usually been the olefin dihydroxylated with the highest degree of enantioselectivity. Availability of (R,R) or (.5,5)-1,2-diphenyl-1,2-ethanediol (also referred to as stilbenediol or dihydrobenzoin) with high enantiomeric purities has led to reports of a number of applications, including incorporation into chiral dioxaphospholanes [50], chiral boronates [51], chiral ketene acetals [52], chiral crown ethers [53], and conversion into 1,2-diphenylethane-1,2-diamines [54]. Dihydroxylation of the substituted rran.r-stilbene 46 with Os04/NMO and DHQD-CLB gives the i ,/ -diol 47 with 82% ee in 88% yield [55]. 

In aqueous acetonitrile, CdS-sensitized irradiation of DPE gave l,l-diphenylethan-l,2-diol along with benzophenone, which indicates that the resulting epoxide is hydrolyzed in the solution (27). 

Treatment of 1,3,2-dioxathiolane. 7,.7-dioxides with telluride ion, generated in situ by reduction of the elemental Te, yields alkenes rapidly (10min-2h) under mild conditions (0°C to rt) <1995TL7209>. The reduction may be performed with 0.1 equiv or less of Te in the presence of a stoichiometric amount of LiEt3BH or NaH. The reaction is stereospecific, for example, / >-2,3-diphenylethane-2,3-diol produces ar-stilbene, and d,l-2,3-diphenylethane-2,3-diol gives trans-stilbene. The sulfates of m-diols are readily converted to ar-alkenes, as shown in Equation (12) <1995TL7209>. 

The enantiomers of thiochroman 1-oxide have been obtained by oxidation of thiochroman in the presence of (R,R)-l,2-diphenylethane-l,2-diol (DPED) or L-diethyl tartrate. In the case of the enantioselective oxidation of thiochroman-4-one, (R,R)-DPED and (V,V)-DPED were used as the chiral inducers <2002CH400>. Fligh yields of both (—)-(R)-thiochroman 1-oxide and (—)-(R)-thiochroman-4-one 1-oxide and with enantioselectivities of 98% and 96%, respectively result from the reaction of H202 with the heterocycles when significant amounts of chloroperox-idase are used as catalyst <1998CH246>. 

We have also examined the use of B(OH)3 and S-proline for the resolution of several other diols. It was observed that l,2-diphenylethane-l,2-diol 7, can be resolved through formation of borate complexes of the type 3 (Scheme 3).7... 

Ole/m synthesis, Eastwood ei al. have reported a new method for conversion of W -diols into alkenes. For example, rut-1,2-diphenylethane-l,2-diol (1) is heated with N,N-dimcthylformamide dimethyl acetal to give 2-dimethylamino-/rani -4.5-diphenyl-1,.3-dioxolanc (2). When this dioxolane is heated with acetic anhydride at 165-180° rruns-stilbene (3) is formed in 80% yield. Similarly, meso-l,2-diphenylethane-l,2-diol is converted into m-stilbene (75%) and a trace of truns-stilbene if the elimination... 

Heating stilbene with benzoyl peroxide and iodine in carbon tetrachloride at 80 °C for 48 h gives an 83% yield of the dibenzoyl ester of hydrobenzoin (l,2-dibenzoxy-l,2-diphenylethane) [230]. Esters of vicinal diols are intermediates in the preparation of diols by the Prevost and the Woodward methods (equation 78). 

Photocatalytic cleavage of 1,2-dioIs [117] or l,2-diphenylethane-l,2-diols [118] with Fe" porphyrin (Fe " (tmpyp)) leads to aldehydes and small quantities of the corresponding acids (eq. (16)). 

Oxidations. Sulfides including P-keto sulfides give optically active sulfoxides by the Sharpless system with modification in using furylhydroperoxides. Alternatively, the tartrate ester may be replaced by (R.R)- or (S,51-diphenylethane-l,2-diol. ... 

W-(p-toluenesulfinyl)bomane-10,2-sultam in the (/Jj-form delivers the sulfinyl group to various nucleophiles. Thus, chiral vinyl sulfoxide and p-toluenesulfinimines are readily prepared. Enantiopure ketones can be obtained from l,2-bis(benzenesulfonyl)alkenes via acetal formation with chiral diols such as (+)-l,2-diphenylethane-l,2-diol. ... 

More importantly, the stereospecific conversion of zne50-l,2-diphenylethane-l,2-diol (12) to Zram-stilbene oxide (13 >99%) with DDPP is consistent with a process... 

Rosini adapted the reaction conditions developed by Uemura and reported on a system using 10 mol % of (S,S)-l,2-diphenylethane-l,2-diol (12) as chiralHgand and tert-butyl hydroperoxide as the terminal oxidant. After optimization of the process, phenyl methyl sulfoxide was obtained in 60% yield with an ee of 80% [24]. 

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