Synthesis and Characterization of Axially Chiral Molecules Containing Dendritic Substituents

Efficient Synthesis of Chiral 1,1′-Binaphthalenes by the Asymmetric Suzuki–Miyaura Reaction: Dramatic Synthetic Improvement by Simple Purification of Naphthylboronic Acids

Naphthylboronic acids prepared as reported in the literature are contaminated with HCl. A very simple purification prior to their use in Suzuki-Miyaura couplings has been found to be crucial, rendering efficient some reactions that had been reported in the literature either to fail or to give extremely poor yields. With this improvement, parent boronic acids can be used instead of esters at moderate temperatures, and bromo derivatives can be used instead of iodo derivatives. Convenient access to chiral sterically hindered binaphthalene derivatives has been achieved through the use of boronic acids, bromonaphthalenes, and ferrocenylphosphane ligands. The products were obtained in good yields (95-55 %) and with good enantioselectivities (90-50 %). Bulkier ligands are less efficient in the coupling of hindered partners.

Synthesis of axially chiral dendrimers containing meta-terphenyl peripheral groups and a chiral binol core

Fréchet-type poly(arylether) dendritic bromides carrying m-terphenyl peripheral groups were synthesised up to second generation by convergent methodology. Simple O-alkylation of chiral (S)-BINOL with the dendritic bromides afforded the corresponding axially chiral dendrimers. The molar optical rotation values of the dendrimers become increasingly negative as the dendrimer generation increases.

Synthesis and photoluminescent properties of 1,1'-binaphthyl-based chiral phenylenevinylene dendrimers

New chiral, soluble binaphthyl derivatives that incorporate stilbenoid dendrons at the 6,6'-positions have been prepared. The synthesis of the new enantiopure dendrimers was performed in a convergent manner by Horner-Wadsworth-Emmons (HWE) reaction of the appropriately functionalized 1,1'-binaphthyl derivative (R)-1 and the appropriate dendrons (R)(2n)G(n)-CHO. Different electroactive units were incorporated in the peripheral positions of the dendrons in order to tune both the optical and electrochemical behavior of these systems. Fluorescence measurements on the chiral dendrimers reveal a strong emission with maxima between 409 and 508 nm depending upon the substitution pattern. Finally, the redox properties of the dendrimers were determined by cyclic voltammetry, showing the influence of the functional groups at the peripheral positions of the dendrimer on the redox behavior of these systems.

Highly diastereoselective synthesis of the 1,1'-binaphthol unit on a bile acid template

The use of 7-deoxycholic acid as a chiral template in the asymmetric syntheses of 1,1'-binaphthyl-2,2'-diol derivatives is reported. Intramolecular coupling of compounds 7 and 11 have been carried out with Mn(acac)(3) in CH(3)CN to afford coupled binaphthol products 8 and 12 with 65% and >99% diastereoselectivity, respectively. In both cases the predominant formation of the (S) isomers were predicted by computer modeling studies. This was confirmed in the case of compound 12.

Synthesis and chiroptical analysis of optically active chiral shell dendrons

We have prepared a series of chiral dendrons (1-4) in which chiral subunits are placed in individual generational shells at varying distances from the focal point. The optical activity of these chiral dendritic structures is successfully modeled using structurally similar low-molecular weight model compounds. In dendrons 1a and 1b a chiral subunit is directly adjacent to the focal point, whereas in dendrons 2, 3, and 4a,b the chiral subunits are incorporated in the interior of the dendron. A marked difference in optical activity between the former 1a and 1b) and latter (2, 3, 4a,b) dendrons is mirrored in the optical activities of model compounds 12a, 12b, 19a, and 19b. These model compounds directly mimic the surrounding constitution of the chiral subunits in the dendrons. This successful analysis of the chiroptical data using low-molecular weight model compounds suggests that these dendrons do not possess conformational order in solution.