Abstract
A convenient approach to the synthesis of multithiacalix[4]arene derivatives containing amino groups and phthalimide fragments by the formation of quaternary ammonium salts is presented. As the initial macrocycle for the synthesis of multithiacalix[4]arenes, a differently substituted p-tert-butylthiacalix[4]arene containing bromoacetamide and three phthalimide fragments was used in a 1,3-alternate conformation. The macrocycle in cone conformation containing the tertiary amino groups was found to be a convenient core for the multithiacalix[4]arene systems. Interaction of the core multithiacalix[4]arene with monobromoacetamide derivatives of p-tert-butylthiacalix[4]arene resulted in formation in high yields of pentakisthiacalix[4]arene containing quaternary ammonium and phthalimide fragments. The removal of phthalimide groups led to the formation of amino multithiacalix[4]arene in a good yield. Based on dynamic light scattering, it was shown that the synthesized amino multithiacalix[4]arene, with pronounced hydrophobic and hydrophilic fragments, formed dendrimer-like nanoparticles in water via direct supramolecular self-assembly.
Highlights
Dendrimers are highly branched macromolecules with nanometer-scale dimensions and are defined by three components: a central core, an interior dendritic structure, and an exterior surface with functional surface groups
Among all of the diverse classes of synthesized dendritic macromolecules, an interesting class is that based on various macrocyclic derivatives, e.g., crown ethers [7,8,9,10], cyclodextrins [11,12,13], pillar[n]arenes [14,15,16], resorcinarenes [17,18], and calix[n]arenes [19,20,21]
As the core of the multithiacalix[4]arenes, we selected previously synthesized tetrasubstituted p-tert-butylthiacalix[4]arene 1 in the cone configuration (Figure 1). It contains polar tertiary amino groups on one side of the macrocycle and lipophilic tert-butyl groups on the opposite side [35]. The choice of this p-tert-butylthiacalix[4]arene as a core is primarily due to its synthetic availability, as well as the presence of reactive tertiary amine groups on sufficiently long spacers, which exclude the influence of the steric factors on the formation of products of incomplete alkylation
Summary
Dendrimers are highly branched macromolecules with nanometer-scale dimensions and are defined by three components: a central core, an interior dendritic structure (branches), and an exterior surface with functional surface groups. The ability to form inclusion complexes, the polyfunctionality of derivatives, and the ability to use spatial organization to create 3D nanoscale systems has attracted researchers to the creation of dendrimers based on macrocyclic derivatives. The tendency to form inclusion compounds [23], the availability of mono-, di-, tri- and tetra-substituted derivatives [24,25,26], as well as the existence of spatially pre-organized conformational isomers [27] (cone, partial cone, 1,2and 1,3-alternate) make the thiacalix[4]arene platform attractive for the preparation of polyfunctional
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