Design of novel functional oxide and its application to catalytic reactions

有机催化因其对环境友好的性质而成为当前合成化学领域的研究热点之一。最近，利用中性Lewis碱的不对称有机催化剂引起了人们的广泛关注，因为它导致了基于功能氧化物的新型手性配体的出现。氧化膦具有高极性和相对较低的Bronsted碱性，其反应活性预计与此类Lewis碱相似。此外，通过商业上可获得的手性膦的简单氧化可以很容易地获得各种类型的手性膦氧化物。然而，手性膦氧化物在不对称有机催化中的应用实例仍然有限。我们研究了由最常见的手性膦配体BINAP容易制备的BINAPO的催化活性。我们发现BINAPO是醛与烯丙基三氯硅烷和对映体…对映选择性烯丙化反应的有效催化剂三氯硅烯醇的更有效的Aldol反应，其中得到的烯丙化加合物或Aldol加合物具有高的非对映选择性和对映体选择性(高达96%ee)。在二异丙乙胺存在下，BINAPO在四氯硅烷与四氯硅烷的对映选择性开环反应中被发现是有效的，提供了相应的氯醇，对映体选择性高达90%ee。本文还研究了联萘二甲酸锂催化的三甲氧基硅烯醇醚的Aldol反应。由环己酮衍生的三甲氧基硅烯醇醚在无水条件下的Aldol反应主要生成具有中等对映体选择性的反Aldol加合物，而在有水条件下的反应主要生成合成产物，且合成产物的对映体选择性大大提高。由1-吲哚衍生的三甲氧基硅烯醇醚与环己烷甲醛(97%ee(Syn))反应具有最好的对映体选择性。这是第一个由手性碱催化的三甲氧基硅烯醇醚的Aldol反应的例子。较少

Organocatalysis has been one of the current hot topics in the field of synthetic chemistry because of its environmentally benign nature. Recently, asymmetric organocatalyses utilizing neutral Lewis bases attracted much attention because it led to the emergence of new types of chiral ligands based on functional oxide compounds. Phosphine oxide has high polarity and relatively low Bronsted basicity, whose reactivity is expected to be similar to those of such Lewis bases. Moreover, various types of chiral phosphine oxides can be easily obtained by the simple oxidation of commercially available chiral phosphines. However, the examples of the application of chiral phosphine oxides to asymmetric organocatalyses are still limited. We investigated the catalytic activity of BINAPO, which is easily prepared from the most common chiral phosphine ligand BINAP. We found that BINAPO was an effective catalyst for the enantioselective allylation of aldehyde with allyltrichlorosilane and the enantiosel … More ective aldol reaction of trichlorosilyl enol, wherein the allylated adducts or aldol adducts were obtained in high diastereo- and enantioselectivities (up tp 96% ee). BINAPO was found to be effective in the enantioselective ring opening of meso-epoxides with tetrachlorosilane in the presence of diisopropylethylamine, affording the corresponding chlorohydrins in high enantioselectivities of up to 90% ee. An aldol reaction of trimethoxysilyl enol ether catalyzed by lithium binaphthoxide was also developed. The aldol reaction of trimethoxysilyl enol ether derived from cyclohexanone under anhydrous conditions predominantly afforded the anti-aldol adduct with moderate enantioselectivity, whereas the reaction under hydrous conditions predominantly resulted in the syn-adduct and the enantioselectivity of the syn-adduct was considerably improved. The best enantioselectivity was obtained in the reaction of trimethoxysilyl enol ether derived from 1-indanone with cyclohexanecarboxaldehyde (97% ee (syn)). This is the first example of an aldol reaction of trimethoxysilyl enol ether catalyzed by a chiral base. Less