Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes
作者:Ewelina Błocka、Mariusz J. Bosiak、Mirosław Wełniak、Agnieszka Ludwiczak、Andrzej Wojtczak
DOI:10.1016/j.tetasy.2014.03.001
日期:2014.4
Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes have been studied with NMR techniques. Among them the complex with the Schiffbase obtained from 2-hydroxy-3-isopropylbenzaldehyde, is the most selective
The β-amino alcohol 1b−Ti(Oi-Pr)4 complex has been shown to catalyze the enantioselective cyanosilylation of aldehydes efficiently. In the presence of 5 mol % of 1b−Ti(Oi-Pr)4 complex catalyst, the aromatic, conjugated, heteroaromatic, and aliphatic aldehydes were converted to their corresponding trimethylsilyl ethers of cyanohydrins in 90−99% yields with up to 94% ee under mild conditions.
β-氨基醇1b -Ti(O i -Pr)4配合物已显示出可有效催化醛的对映选择性氰基硅烷化反应。在5摩尔%的1b -Ti(O i -Pr)4络合催化剂存在下,芳族,共轭,杂芳族和脂族醛以90-99%的产率转化为相应的氰醇三甲基甲硅烷基醚,产率最高为94 %ee在温和条件下。
Synthesis of the bifunctional BINOL ligands and their applications in the asymmetric additions to carbonyl compounds
作者:Ying-Chuan Qin、Lan Liu、Michal Sabat、Lin Pu
DOI:10.1016/j.tet.2006.06.049
日期:2006.10
the diphenylzinc addition which often require the addition of a significant amount of diethylzinc with cooling (or heating) the reaction mixture in order to achieve high enantioselectivity, using (S)-8 needs no additive and gives excellent results at room temperature. (S)-8 in combination with diethylzinc and Ti(OiPr)4 can catalyze the highly enantioselective phenylacetylene addition to aromatic aldehydes
分别从BINOL和H 8 BINOL与吗啉代甲醇的反应中开发了双功能BINOL和H 8 BINOL配体(S)-6和(S)-8的高效一步合成方法。这些化合物的X射线分析表明它们在结构上有相似之处和不同之处。双功能H 8 BINOL(S)-8已发现对二苯基锌与许多脂族和芳族醛的反应具有很高的对映选择性,尤其是对于线性脂族醛而言,对映选择性最强的催化剂。与开发用于添加二苯锌的其他催化剂不同,该催化剂通常需要在冷却(或加热)的同时添加大量的二乙基锌以实现高对映选择性,使用(S)-8无需添加剂,在室温下可获得优异的结果温度。(S)-8与二乙基锌和Ti(O i Pr)4结合可以催化高度对映选择性的苯乙炔加成芳族醛。尽管对映选择性还不是很高,但它在室温下还可以促进苯乙炔向苯乙酮的添加。在不使用Ti(O i Pr)4和路易斯碱添加剂的情况下,(S)-8与二乙基锌结合可以催化丙酸甲酯与醛的反应,形成高官能度
Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate
作者:Michael North、Marta Omedes-Pujol
DOI:10.3762/bjoc.6.119
日期:——
Propylene carbonate can be used as a green solvent for the asymmetricsynthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding reactions carried out in dichloromethane. A mechanistic study has been undertaken, comparing the catalytic activity of VO(salen)NCS in propylene carbonate
The Asymmetric Addition of Trimethylsilyl Cyanide to Aldehydes Catalyzed by Chiral (Salen)Titanium Complexes
作者:Yuri N. Belokon'、Susana Caveda-Cepas、Brendan Green、Nicolai S. Ikonnikov、Viktor N. Khrustalev、Vladimir S. Larichev、Margarita A. Moscalenko、Michael North、Charles Orizu、Vitali I. Tararov、Michela Tasinazzo、Galina I. Timofeeva、Lidia V. Yashkina
DOI:10.1021/ja984197v
日期:1999.4.1
The use of chiral (salen)TiCl2 complexes to induce the asymmetricaddition of trimethylsilyl cyanide to aldehydes has been investigated. The complexes are catalytically active at substrate-to-catalyst ratios as high as 1000:1, and the optimal catalyst (2e) which is derived from (R,R)-1,2-diaminocyclohexane and 3,5-di-tert-butyl-2-hydroxybenzaldehyde produces trimethylsilyl ethers of cyanohydrins with