Facile Synthesis of a Tadpole-Shaped Dendrimer Based on N-Alkylated Oligo(p-benzamide)

Abstract

A novel, rapid, inexpensive, and highly accelerated approach for the synthesis of a tadpole-shaped dendrimer possessing monodisperse N-alkylated oligo(p-benzamide) as a rod block with a precise length and an amine-terminated dendritic block based on 3,5-diaminobenzoic acid has been developed. The N-alkylated oligo(p-benzamide)s were prepared by an rapid stepwise method using thionyl chloride as an activating agent and trifluoroacetamide as the protecting group for the end amine, in which the number of amide units dramatically propagated only through every deprotection and condensation. From this rod block, each generation of dendron rod molecules was formed divergently using 3,5-bis(trifluoroacetamido)benzoyl chloride as an AB2 building block.

Dendron-Mediated Self-Assembly, Disassembly, and Self-Organization of Complex Systems

“…Dendronization of a single chain end of rigid polymers (Figure 1, third row second from right, and Figure 198, first row left) such as oligo(p-phenylenes), [757][758][759] oligo(benzamides), 760 poly(phenylene ethynylene), 613 or poly(biphenyl esters) 761 also leads to a diverse array of self-organized architectures. Because of their rigid oblate shapes, the linear segments alone often exhibit N and S phases.…”

N‐Alkylated Aromatic Poly‐ and Oligoamides

“…This was mostly achieved using N-protected N-alkylated monomeric aromatic derivatives, activating the carboxylic acid as the corresponding acid chloride prior to the coupling step. Various N-protecting groups were employed, comprising for example trifluoroacetate [40] and o-or p-nitrobenzenesulfonyl (nosyl) to access oligo(p-benzamide)s [41] and oligo (pyridyl amide)s (Scheme 4). [42] The latter could also serve for the synthesis of secondary amines by means of Fukuyama's nosyl methodology.…”

“…To access longer oligomers, an efficient block-coupling approach was preferred as illustrated by Ueda and co-workers in the preparation of N-alkylated oligo(p-benzamide)s comprising up to sixteen residues. [40] The monomer synthesis using acid chloride derivatives was also performed in a bi-directional manner to access symmetrical pyridine-containing N-methyl aromatic oligoamides [17c] and unsymmetrical N-methyl aromatic amide oligomers. [12a] Kilbinger and coworkers were the first to describe the solid-phase synthesis of N-substituted oligo(p-benzamide)s up to decamer length using a Wang resin support and a Fmoc-based strategy.…”

“…This strategy has for example led to the development of strongly aggregating poly(benzamide)s with a rod-like conformation or rod-coil conformation when associated with PEG coil block polymers. [44a] In addition, the well-controlled chain-growth polycondensation developed by Yokosawa and co-workers for the synthesis of poly(benzamide)s with narrow polydispersity, [27] has allowed for the access to a wide range of polymer and copolymer architectures: star-shaped polymers with a porphyrin core [64] or a microgel core made from diacrylamides, [35] tadpole-shaped dendrimers [40] and hyperbranched polymers. [65] The optical properties of oligothiophenes attached to cyclic meta-or para-benzamide trimers and polymers were studied by Takagi and co-workers.…”

Synthesis of Aliphatic Polyamide Dendrimers Based on Facile Convergent Method

“…These specifities have encouraged the pursuit of new polymeric materials for applications in areas, such as catalysts, liquid crystals, photonic devices, and drug delivery systems. − Although dendrimers have received much attention as new materials, their widespread uses were interfered because the synthesis of dendrimers requires a tedious multistep procedure with repetitive protection–deprotection and purification processes. To solve this problem, we have focused on the development of facile synthetic approaches of dendrimers, and reported the rapid syntheses of aromatic polyamide dendrimers via both divergent and convergent methods, − in which the total number of reactions decreased to half that required in the conventional approaches. Whereas a few aromatic polyamide dendrimers have been reported as functional materials, there are many reports on the development of aliphatic polyamide dendrimers , as the functional materials, such as polyamide amine (PAMAM) dendrimers, lysine dendrimers and airbol.…”