Development of Asymmetric Reactions Catalyzed by Bronsted Acid in Aqueous Media

我们发现，在Bronsted酸(典型的AQ)的影响下，Mannich类型的反应顺利进行。HbF4，在有机水溶液中高产率地合成相应的(β-氨基)羰基化合物。此外，在无有机溶剂条件下，水中十二烷基硫酸钠存在下，HbF4催化的Mannich反应顺利进行。成功地实现了水介质中的氮杂-Diels Alder反应。研究了乙二胺与α-氧基酯衍生的烯酮硅缩醛在HbF_4催化下的Mannich式反应的反立体选择性和立体选择性。在异丙醇水溶液中使用芳基酯衍生的缩酮硅醛得到的反β-氨基-α-硅氧基酯具有良好的立体选择性，而在十二烷基硫酸钠存在下，在水中使用芳酯衍生的缩酮硅醛可以优先得到合成的异构体。

We have found that Mannich-type reactions took place smoothly under the influence of Bronsted acid, typically aq. HBF_4, to afford the corresponding (β-amino carbonyl compounds in high yields in aqueous organic solvents. Furthermore, the HBF_4-catalyzed Mannich-type reaction took place smoothly in the presence of sodium dodecyl sulfate in water under organic solvent-free conditions. Aza-Diels Alder reactions in aqueous media have been successfully achieved. Anti and syn stereoselectivity on the HBF_4-catalyzed Mannich-type reaction of ketene silyl acetal derived from α-oxy esters with aldimines were investigated. Whereas use of ketene silyl acetal derived from aryl ester in aqueous 2-propanol gave anti β-amino-α-siloxy ester with excellent stereoselectivity, use of ketene silyl acetal derived from methyl ester in water in the presence of sodium dodecyl sulfate gave the syn isomer preferentially.