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聚合物固载的1,2-二醇(1—3)和1,3-二醇(4,5)作为醛或酮的保护基团已有广泛的研究。聚合物固载的保护试剂的重要特性是能够对双功能基化合物进行单保护。上述二醇树脂用于对苯二甲醛单保护中只有在很低的醛固载量(0.2—0.38mmol/g)时才是成功的。其单保护率可达95％以上。一旦固载的醛量增加,其单保护率迅速降低。而且这些二醇树脂多数不能再生重复使用。从这些二醇聚合物的结构分析可以看出,它们对二醛单保护率低的原因很可能是功能基通过醚键或酯键同聚合物相连,其柔性增加了二醛双结合的可能性。为了克服这些树脂的缺点,我们设计合成了二醇功能基直接与聚苯乙烯链的苯环相接的1,3-二醇树脂——1-聚苯乙烯基-2,2-二甲基-1,3-丙二醇(6)。二醇功能基2位上的两个氢原子均被甲基所取代,减少了在被保护的醛解脱过程中二醇功能基脱水失活的可能性,以增加功能基的可再生性。
Polymeric supported 1,2-diols (1-3) and 1,3-diols (4,5) have been extensively studied as protecting groups for aldehydes or ketones. An important property of polymer-supported protection reagents is the ability to single-protect bifunctional compounds. The above-mentioned diol resin was successfully used in the mono-protection of para-phthalaldehyde only at low aldehyde loadings (0.2-0.38 mmol / g). The single protection rate of up to 95%. Once the amount of aldehyde loaded increases, the single protection rate decreases rapidly. Moreover, most of these diol resins can not be recycled for reuse. From the structural analysis of these diol polymers, it can be seen that the reason for their low single protection to dialdehyde is probably that the functional groups are linked to the polymer through ether or ester linkages and that their flexibility increases the probability of double-dialdehyde binding . In order to overcome the shortcomings of these resins, we designed and synthesized a 1,3-diol resin, 1-polystyryl-2,2-dimethyl -1,3-propanediol (6). Both hydrogen atoms in the 2-position of the diol functional group are replaced by methyl groups, reducing the possibility of dehydration of the diol functional groups during the liberation of the protected aldehydes to increase the functional group’s reproducibility.