Sequential silyl aldol condensation in controlled synthesis of living poly(vinyl alcohol) precursors
Sequential silyl aldol condensation in controlled synthesis of living poly(vinyl alcohol) precursors
复制标题
活性聚（乙烯醇）前体的受控合成中的顺序硅醇醛缩合
DOI：
10.1021/ma00160a052
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发表时间：
1986
期刊：
影响因子：
5.5
通讯作者：
O. Webster
中科院分区：
文献类型：
--
作者：
D. Y. Sogah;O. Webster
前体 71 迈克尔加成和羟醛缩合构成了一组重要的可用于碳-碳键形成的有机反应。我们最近报道了前者在丙烯酸聚合物的控制合成中的应用。 2 该方法称为基团转移聚合 (GTP)，可产生分子量控制良好的单分散活性甲基丙烯酸酯聚合物。在本次通讯中，我们描述了甲硅烷基醛醇缩合在直接合成活性大分子中的首次应用，其结构和分子量由引发剂控制。已知醛与甲硅烷基乙烯基醚反应生成甲硅烷基化交叉醛醇产物。 4 由于甲硅烷基乙烯基醚的羟醛缩合会形成新的醛基，因此继续添加甲硅烷基乙烯基醚应得到聚合物。我们发现，将数倍过量的甲硅烷基乙烯基醚 l4® 添加到作为引发剂的苯甲醛中，得到带有末端醛基的甲硅烷基化乙烯醇聚合物（方案 I）。如表I所示的聚合物的分子量由甲硅烷基乙烯基醚与醛引发剂的摩尔比控制。与甲基丙烯酸甲酯的GTP中甲硅烷基基团从引发剂转移到单体不同，甲硅烷基乙烯基醚的聚合（下文称为羟醛-GTP）涉及甲硅烷基基团从单体转移到引发剂。该产品是稳定的中性活性聚合物，其水解稳定性取决于甲硅烷基的体积。与相应的三甲基硅醚相比，叔丁基二甲基硅醚具有众所周知的增强的水解稳定性，5 我们发现，在较宽的温度范围（-80 至 + 70°C）内，使用叔丁基二甲基硅基乙烯基醚可以获得最佳的分子量控制。 6 该过程的发生需要催化剂。虽然
Precursors71 Michael addition and aldol condensation constitute an important group of organic reactions available for car-bon-carbon bond formation. We recently reported ap-plication of the former to controlled synthesis of acrylic polymers. 2 The method, termed group-transfer polymerization (GTP), give monodisperse living3 methacrylate polymers of well-controlled molecular weight. In this communication we describe the first application of silyl aldol condensation to direct synthesis of living macro-molecules whose structure and molecular weight are con-trolled by the initiator.Aldehydes are known to react with silyl vinyl ethers to give silylated crossed-aldolproducts. 4 Since a new aldehyde group is formed in aldol condensation of silyl vinyl ethers, continued addition of the silyl vinyl ether should give a polymer. We find that addition of a several-fold excess of silyl vinyl ether l4® to benzaldehyde as initiator gives a silylated vinyl alcohol polymer with a terminal aldehyde group (Scheme I). The molecular weight of the polymer as shown in Table I is controlled by the molar ratio of the silyl vinyl etherto the aldehyde initiator. Unlike GTP of methyl methacrylate in whichthe silyl group is transferred from the initiator to the monomer, the polymerization of silyl vinyl ethers, hereafter referred to as aldol-GTP, involves a transfer of the silyl group from monomer to initiator. The products are stable, neutral living polymers whose hydrolytic stability depends on the bulkiness of the silyl group. In line with the well-known enhanced hydrolytic stability of ieri-butyldimethylsilyl ethers compared to the corresponding trimethylsilyl ethers, 5 we find that the best control of molecular weight is obtained with tert-butyldimethylsilyl vinyl ethers over a wide temperature range (-80 to+ 70 C). 6 A catalyst is required for the process to occur. Although