High-Yield Synthesis of Dendrimers through Alternate Multiaddition Reactions with Commercially Available Reagents
作者:Ken’ichi Aoki、Kunihiro Ichimura
DOI:10.1246/bcsj.20110024
日期:2011.11.15
An alternate multiaddition (AMA) process consisting of Michael addition and urethane formation is proposed to achieve the quantity synthesis of dendrimers without by-product formation and any weight loss by using commercially available compounds. α-Thioglycerol (TG) was added to pentaerythritol tetraacrylate (PETA) to give the corresponding octaol, but the subsequent reaction with 1,1-bis(acryloyloxymethyl)ethyl isocyanate (BEI) resulted in incomplete urethane formation because of the steric effect of the secondary OH groups. The replacement of BEI with 2-isocyanatoethyl acrylate (AOI) improved the efficiency of the addition of NCO to the secondary OH groups, but an excess amount of AOI was required. Subsequently, we employed the combination of PETA, 2-sulfanylethanol (SE), and BEI. The addition of SE to PETA produced readily the tetraol, which was reacted with BEI to afford dendritic octaacrylate (Ac8b). The repetition of the two addition reactions gave dendritic octaol and hexadecylacrylate (Ac16b), respectively, in large scales. The base-catalyzed Michael addition of 2-naphthalenethiol to acrylate residues of Ac8a and Ac16b gave naphthylthio-terminated dendrimers N8b and N16b, respectively, which were purified by column chromatography. GPC as well as UV-spectroscopic analysis of N8b and N16b revealed that N8b is reasonably monodispersed whereas the purity of N16b is slightly reduced.
本研究提出了一种由迈克尔加成和脲烷形成组成的交替多重加成(AMA)工艺,利用市场上可买到的化合物实现了树枝状聚合物的定量合成,且无副产物生成和任何重量损失。在季戊四醇四丙烯酸酯(PETA)中加入α-硫代甘油(TG)可得到相应的辛醇,但随后与 1,1-双(丙烯酰氧基甲基)异氰酸乙酯(BEI)反应时,由于仲羟基的立体效应,聚氨酯形成不完全。用 2-异氰酸乙基丙烯酸酯(AOI)代替 BEI,提高了 NCO 与仲羟基加成的效率,但需要过量的 AOI。随后,我们采用了 PETA、2-sulfanylethanol(SE)和 BEI 的组合。在 PETA 中加入 SE 很容易生成四醇,四醇与 BEI 反应生成树枝状八丙烯酸酯(Ac8b)。重复这两个加成反应,可分别得到大规模的树枝状辛醇和十六烷基丙烯酸酯(Ac16b)。在碱催化下,2-萘硫醇与 Ac8a 和 Ac16b 的丙烯酸酯残基发生迈克尔加成反应,分别得到萘硫基封端树枝状聚合物 N8b 和 N16b,并通过柱层析法纯化。对 N8b 和 N16b 进行的 GPC 和紫外光谱分析显示,N8b 的单分散性较好,而 N16b 的纯度则略有降低。