Dendrimers with inherently axially chiral units

Lellek, Vit; Stibor, Ivan

doi:10.1039/a907825h

Cited by 16 publications

(10 citation statements)

References 30 publications

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“…Similar results were obtained 78 by Lellek et al who prepared chiral dendrimers using 1,1'-binaphthol unit derivatives of different configuration as the dendritic building blocks. As observed 77 by Chow and co-workers in the case of the polytartrate dendrimers, the molar rotation and the specific rotation values for the binaphthol-based dendrimers obeyed a linear relationship with respect to the number of chiral monomer units.…”

Section: Dendrimers Featuring Chiral Branched Unitssupporting

confidence: 87%

Chiral dendrimers—from architecturally interesting hyperbranched macromolecules to functional materials

Romagnoli

Hayes

2002

J. Mater. Chem.

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Section: Dendrimers Featuring Chiral Branched Unitssupporting

confidence: 87%

Chiral dendrimers—from architecturally interesting hyperbranched macromolecules to functional materials

Romagnoli

Hayes

2002

J. Mater. Chem.

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“…In addition, these linkers convey spectroscopically unique signatures to different regions of the dendrimer architecture; an effect only rarely observed in related architectures. [24][25][26][27][28][29] …”

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confidence: 99%

Identification of diamine linkers with differing reactivity and their application in the synthesis of melamine dendrimers

Moreno

Simanek

2008

Tetrahedron Letters

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Diamine linkers for the synthesis of dendrimers based on melamine were identified using competition reactions. The relative reactivity of the cyclic monoamines surveyed vary in relative reactivity by 40 times, expanding the previously identified series to an overall relative reactivity range of 320 times. Azetidine is 40 times more reactive than the cyclic, nine-membered ring (C 8 H 17 N), and 320 times more reactive than benzylamine. Reactivity differences are attributed to pKa values and sterics. Incorporating these groups into diamines provides linkers that can be employed in dendrimer synthesis. Specifically, the nucleophilicity of the individual amine groups comprising 3-aminoazetidine, 3-aminopyrrolidine, and 4-aminopiperidine vary by 100 times, 70 times, and 20 times, respectively. These linkers are incorporated into a generation three dendrimer.Our group has invested significant energies in the synthesis of dendrimers based on triazines, also referred to as dendrimers based on melamine deriving from our use of diamine linkers. 1, 2 Our early targets commonly incorporated p-aminobenzylamine because of the significant differences in the reactivity of the amines of this group. That is, during a convergent synthesis, protecting group manipulations and functional group interconversions could be avoided because the benzylic amine would react preferentially (essentially exclusively) with the monochlorotriazine dendron being elaborated. 1,[3][4][5][6][7] The low stability of these aniline derivatives required reasonable, but additional, care on handling. While the use of distilled solvents and inert atmospheres are not uncommon, nor is the requirement for refrigerated storage of intermediates, we recognized that these precautions could impact the broader acceptance of these materials.The low cost and high reactivity of piperazine soon made it a linking diamine of choice for our investigations. However, when using piperazine, dimerization of monochlorotriazines was observed under non-ideal reaction conditions that were usually attributed to concentration, rate of addition, ineffective stirring or lack thereof, temperature of addition and the magnitude of stoichiometric excess. 4,[8][9][10][11][12][13][14][15][16][17][18] Reactions with either p-aminobenzylamine or piperazine could be readily followed by NMR. The shift of the benzylic protons on reaction with the monochlorotriazine dendron or the desymmetrization of methylene groups of the piperazine group were diagnostic. The use of piperazine led to the undesirable formation of dimers, unfortunately. Detecting these dimers by NMR proves difficult due to signal degeneracy between the desired asymmetric monoamine and the symmetric dimer.

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“…Another study of diastereoisomeric dendrimers was reported by Lellek and Stibor, 19 who examined the structural features of homochiral isomer 14a (Fig. 10), based on (R)-2,2 0dimethoxy-1,1 0 -binaphthalene building blocks, and its heterochiral partner 14b.…”

Section: Cotton Effect Cementioning

confidence: 99%

The quest for secondary structure in chiral dendrimers

Rendell

2008

Chem. Commun.

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This review highlights important developments in the pursuit of chiral conformational order in dendritic structures. To be able to create and control chiral secondary structure necessitates a thorough understanding of how chiral subunits influence the macroscopic structure. Recent studies involve highly sophisticated manipulation of macroscopic chirality through a creative combination of a wide range of synthetic, computational and analytical techniques.

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Dendrimers with inherently axially chiral units

Cited by 16 publications

References 30 publications

Chiral dendrimers—from architecturally interesting hyperbranched macromolecules to functional materials

Chiral dendrimers—from architecturally interesting hyperbranched macromolecules to functional materials

Identification of diamine linkers with differing reactivity and their application in the synthesis of melamine dendrimers

The quest for secondary structure in chiral dendrimers

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