Synthesis and Characterization of New Enantiopure 7,7′-Disubstituted 2,2′-Dihydroxy-1,1′-binaphthyls: Useful Ligands for the Asymmetric Allylation Reaction of Aldehydes

Atropisomeric (R,R)-2,2‘-Bi([2]paracyclo[2](5,8)quinolinophane) and (R,R)-1,1‘-Bi([2]paracyclo[2](5,8)isoquinolinophane): Synthesis, Structural Analysis, and Chiroptical Properties

“…First of all, as noticed above, the comparison of the absorption spectra shows that both ( R , R ) - 2 and ( R )-8,8‘-dimethyl-1,1‘-biisoquinoline [ ( R )-11 ] strongly contain the same distorted 1,1‘-biisoquinoline chromophore, the difference in shape occurring in the 250−200 nm range could be due to the fact that while the dihedral angle of ( R )-11 is of the order of 90−100°,9a the present MM calculation gives a much smaller dihedral angle (72°) in ( R , R )-2 . This is in keeping with the UV spectrum of ( R , R )-2 , where a sequence of less intense (longer wavelength)/more intense (shorter wavelength) absorption bands is observed between 250 and 200 nm, characteristic of a biaryl possessing a small θ angle . In addition, our MM calculations show that the ( R,R ) planar chirality of ( R , R )-2 induces a positive twist of the 1,1‘-biisoquinoline moiety.…”

“…In particular, in the case of ( R , R )-2 , the 350−250 nm range possesses a positive, broad, and very intense Cotton effect, while a negative, well-defined, and less intense CD band is observed for ( R )-11 . In addition, the intensity of the couplet at 220−230 nm in the spectrum of ( R , R )-2 is much smaller than that of a model compound ( R )-11 (note that θ in ( R )-11 is 90−100° and shows a couplet with Δε −200, +200, a distortion of 72° should induce an even more intense couplet) . These observations suggest that a “perturbed”, distorted 1,1‘-biisoquinoline chromophore, is really responsible for the spectroscopic properties of ( R , R )-2 is where by “perturbation” we intend the effect of the paracyclophane moieties which cannot be neglected in order to completely explain the optical activity of this molecule.…”

In the Arena of Enantioselective Synthesis, Titanium Complexes Wear the Laurel Wreath

“…The ligand 90an emerged as the best one from a screening of five symmetrical 7,7-disubstituted binaphthol compounds. 316 The enantioselectivity found for the addition of the allyl tin derivative 221a to benzaldehyde using 20 mol % of both ligand 90an and dichlorotitanium diisopropoxide (58b) was as high as 92%, similar to that obtained using BINOL. The phenol derivative 226 has also been tested in the enantioselective addition of allyl tin derivative 221a to aldehydes in the presence of catalytic amounts of titanium tetraisopropoxide.…”

Chiroptical Properties of Chiral Macrocycles Composed of Axially Chiral Binaphthyl and Bithiophene

“…The synthesis of the macrocyclic compounds [2]‐ 1 and [3]‐ 1 is shown in Scheme 1. We started with the enantiomer of 7,7’‐dibromo‐2,2’‐dimethoxy‐1,1’‐binaphthyl ( R a )‐ 2 or ( S a )‐ 2 , prepared according to previous literature [11,16] . The reactions were performed individually for each enantiomer.…”

“…We started with the enantiomer of 7,7'dibromo-2,2'-dimethoxy-1,1'-binaphthyl (R a )-2 or (S a )-2,p repared according to previous literature. [11,16] The reactions were performed individually for each enantiomer. Stille coupling with 2-(tributylstannyl)thiophene afforded 3,w hich was subjected to successive bromination with N-Bromosuccinimide (NBS) to afford 4.T he bis(1,5-cyclooctadiene)nickel(0)-catalyzed homocoupling reaction of 4 together with 1,5-cyclooctadiene (cod) and 2,2'-bipyridyl to give cyclic dimer [2]-1 and trimer [3]-1 along with insoluble components that were presumably acyclic higher oligomers.…”