アミン-N-オキシドを触媒とする新規不斉合成反応の開発

虽然有充分的文献证明，胺n-氧化物作为强大的电子对供体与各种受体分子形成配合物，但胺n-氧化物作为配体或催化剂的合成用途仍有待开发。我们发展了以下n -氧化物诱导的有机反应。(1)发现联吡啶N，N'-二氧化氮是甲基三氧铈催化烯烃过氧化氢环氧化反应的理想配体。(2)利用(S)-3,3'-二甲基-2,2'-双喹啉N，N'-二氧化氮作为催化剂，一种新的对映选择性烯丙基醛与烯丙基硅烷的催化烯丙基化反应，使均烯丙醇具有几乎完全的非对映选择性和高达92% ee的高对映选择性，其中使用二异丙基乙胺作为添加剂已被证明对加速催化循环至关重要。同样值得注意的是，上述发现代表了利用胺n -氧化物作为手性催化剂的不对称反应的第一个成功例子。在上述烯丙基化反应的基础上，提出了一种由烯丙基卤化物制备具有光学活性的均烯丙基醇的一锅简便方法。在氯化亚铜和叔胺的存在下，由烯丙基卤化物和三氯硅烷原位合成了烯丙基三氯硅烷。在不分离丙烯基三氯硅烷的情况下，将苯甲醛和手性联喹啉N、N -二氧化氮引入同一烧瓶中，得到相应的均烯丙醇，对映选择性好至高。(3) (S)-3,3'-二甲基-2,2'-双喹啉N，N'-二氯化镉配合物是一种很好的催化剂，用于硫醇与烯酮的不对称共轭加成，对映选择性高达79% ee。

Although it is well documented that amine N-oxides act as powerful electron-pair donors to form complexes with a variety of acceptor molecules, synthetic utility of amine N-oxides as ligands or catalysts still remains to be developed. We have developed the following N-oxide-induced organic reactions. (1) Bipyridine N,N'-dioxide was found to be a felicitous ligand for methyltrioxorhenium-catalyzed epoxidation of olefins with hydrogen peroxide. (2) A new catalytic, enantioselective allylation of aldehydes with allyltrichlorosilanes exploiting (S)-3,3'-dimethyl-2,2'-biquinoline N,N'-dioxide as a catalyst affords homoallylic alcohols in virtually complete diastereoselectivities and high enantioselectivities of up to 92% ee, wherein the use of diisopropylethylamine as an additive has proven to be crucial for the acceleration of the catalytic cycle. It is also noteworthy that the above finding represents the first successful example of asymmetric reactions utilizing amine N-oxide as a chiral catalyst. A one-pot, convenient method for the preparation of optically active homoallylic alcohols from allyl halides was developed based on the above allylation. Allyltrichlorosilanes were generated in situ from allyl halides and trichlorosilane in the presence of cuprous chloride and tertiary amine. Without isolation of the allyltrichlorosilanes, benzaldehyde and chiral biquinoline N,N'-dioxide were introduced into the same flask, producing the corresponding homoallylic alcohols in good to high enantioselectivities. (3) (S)-3,3'-dimethyl-2,2'-biquinoline N,N'-dioxide-cadmium chloride complex was proven to be a good catalyst for the asymmetric conjugate addition of thiols to enones with enantioselectivit of up to 79% ee.