“…The 1 H NMR spectrum of this compound shows its C 2 symmetry with a singlet observed at δ 3.81 for the two methyl groups. This also demonstrates that no diastereomeric isomers arose from the bulky adamantanyl-substituted 3,3‘-aryl groups unlike what we observed in the analogous 3,3‘-naphthyl compounds . That is, the rotation barrier for the 3,3‘-aryl groups around the aryl−aryl single bonds of ( S )- 4 is still very small.…”
[reaction: see text] Methodology for the stereoselective preparation of both (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated esters is described. 1-Bromo-1-fluoroalkenes (E/Z approximate 1:1) can be isomerized to high E/Z ratio mixtures, which participate in palladium-catalyzed carboalkoxylation and lead to (Z)-alpha-fluoro-alpha,beta-unsaturated esters in high stereoselectivity. The same starting material can also be kinetically reduced to get an E/Z ratio of 0:100; similar carboalkoxylation reaction at 70 degrees C affords (E)-alpha-fluoro-alpha,beta-unsaturated esters stereospecifically.
“…The 1 H NMR spectrum of this compound shows its C 2 symmetry with a singlet observed at δ 3.81 for the two methyl groups. This also demonstrates that no diastereomeric isomers arose from the bulky adamantanyl-substituted 3,3‘-aryl groups unlike what we observed in the analogous 3,3‘-naphthyl compounds . That is, the rotation barrier for the 3,3‘-aryl groups around the aryl−aryl single bonds of ( S )- 4 is still very small.…”
[reaction: see text] Methodology for the stereoselective preparation of both (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated esters is described. 1-Bromo-1-fluoroalkenes (E/Z approximate 1:1) can be isomerized to high E/Z ratio mixtures, which participate in palladium-catalyzed carboalkoxylation and lead to (Z)-alpha-fluoro-alpha,beta-unsaturated esters in high stereoselectivity. The same starting material can also be kinetically reduced to get an E/Z ratio of 0:100; similar carboalkoxylation reaction at 70 degrees C affords (E)-alpha-fluoro-alpha,beta-unsaturated esters stereospecifically.
“…For O , O -ligands, 1,1‘-bi-2-naphthol (BINOL) derivatives are important because of their simple C 2 -symmetric structures and synthetic utility. Particularly, Ti(IV)−BINOLate complex ( 2 ) has been developed by using type b catalysis. 8b, The 3,3‘-di( o -alkoxyphenyl)-BINOL ( 3 ) described by Pu and co-workers, which has overcome the problem associated with the use of excess Ti(O i Pr) 4 , can be also classified as a neighboring acid−base catalytic system, type b. , In brief, these type b catalyses involve only the terminal acid and base functions without conjugation inside the ligands. 2 Precedent acid−base catalytic systems by type b.…”
A highly enantioselective dialkylzinc (R(2)(2)Zn) addition to a series of aromatic, aliphatic, and heteroaromatic aldehydes (5) was developed based on conjugate Lewis acid-Lewis base catalysis. Bifunctional BINOL ligands bearing phosphine oxides [P(=O)R(2)] (7), phosphonates [P(=O)(OR)(2)] (8 and 9), or phosphoramides [P(=O)(NR(2))(2)] (10) at the 3,3'-positions were prepared by using a phospho-Fries rearrangement as a key step. The coordination of a NaphO-Zn(II)-R(2) center as a Lewis acid to a carbonyl group in a substrate and the activation of R(2)(2)Zn(II) with a phosphoryl group (P=O) as a Lewis base in the 3,3'-diphosphoryl-BINOL-Zn(II) catalyst could promote carbon-carbon bond formation with high enantioselectivities (up to >99% ee). Mechanistic studies were performed by X-ray analyses of a free ligand (7) and a tetranuclear Zn(II) cluster (21), a 31P NMR experiment on Zn(II) complexes, an absence of nonlinear effect between the ligand (7) and Et-adduct of benzaldehyde, and stoichiometric reactions with some chiral or achiral Zn(II) complexes to propose a transition-state assembly including monomeric active intermediates.
“…26,27 (S)-M-1 and (R)-M-1 were synthesized from (S) and (R)-BINOL (Scheme 1) respectively according to the literature. 13,28 (S)-M-1 and (R)-M-1 served as the monomers for the synthesis of the desired chiral polymers. They can also be used as the starting materials or building blocks to prepare the novel chiral catalysts, molecular recognition and the polarized light-emitting sensors.…”
ABSTRACT:Four chiral conjugated polymer-1 (P-1), polymer-2 (P-2), polymer-3 (P-3) and polymer-4 (P-4) were obtained by the polymerization of (S)-6,60 -dibromo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((S)-M-1) and (R)-6,6 0 -dibromo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((R)-M-1) with 1,4-divinyl-2,5-dibutoxybenzene (M-2) and 1,3,4-oxadiazole-2,5- 1-4 (R) or (S)-1,1 0 -binaphthol (BINOL) have often been used as the starting materials for obtaining chiral binaphthyl compounds. The 2,2 0 -hydroxyl groups of BINOL can be easily converted into other functional groups and the 3,3 0 -and 6,6 0 -positions of binaphthyl skeletal structure of BINOL can be selectively functionalized at the well-defined molecular level, leading to a variety of binaphthyl derivatives which can exhibit remarkably stable chiral configuration as well as high chiral induction in molecular recognition, 5-9 asymmetric processes.10-15 These rigid and sterically chiral polybinaphthyl polymers also represent a new generation of materials for applications in chiral sensors, polarized light emission and nonlinear optical materials. [16][17][18][19][20] Conjugated polymers with rigid -systems often possess poor solubility, which seriously inhibits full structural elucidations and property investigations. We choose M-2 and M-3 as the conjugated molecular bridge linkers. Oxadiazole derivatives have been widely used as electron transporting/hole blocking materials in LED devices and LED blends because oxadiazole unit has many excellent properties on the better chromophore, high thermal and oxidative stability, and the good charge injection and transporting building blocks. [21][22][23] In our paper, M-3, 1,3,4-oxadiazole-2,5-bis(4-vinylbenzene) is introduced into the chiral polymers main chain backbone to maintain conjugation between the oxadiazole and binaphthyl segments so that the electron transporting properties of the polymers may be improved. In addition, by introducing oxadiazole, an electron deficient moiety into the main chain, the electron density may shift away from the vinyl bond, which could increase the stability of the resulting chiral polymers. 24,25 To make soluble conjugated polymers, the alkyl groups substitutents on the phenyl and binaphthyl rings as side chain of the polymers can improve solubility in organic solvents and facile electro-optical sensors. Heck, Suzuki, Stille and Sonogashira reactions are the most important C-C coupling reactions in organic chemistry synthesis. Herein, we present preliminary results of synthesis and properties of four polymers based on the chiral unit 1,1 0 -binaphthyl structure. The four chiral polymers containing vinylene linkages between naphthyl and phenyl groups can reduce steric hindrance between backbone rings and groups, and also have a beneficial effect on delocalizable -electronic conjugation structure of polymers. These polymers are green-blue light emitting materials with very good fluorescence quantum efficiencies.
EXPERIMENTAL
General1 H, 13 C NMR spectra measurements (all in CDCl 3 ) were recorded...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
