合成并测试了新的双功能阻转异构硫脲1作为非对映异构体(a R / a S)-(R,R)-1的混合物以及作为单一非对映异构体(a R)-(R,R)-1和(a R)-(S,S)-1在一系列醛(芳族和脂族)的有机催化,对映选择性,氰基硅烷化反应中进行。获得了适度的对映体过量(至多69%ee)和定量收率。使用硫脲非对映异构体的混合物(R / aS)-(R,R)-1而不是单个非对映异构体。
Anionic chiral cobalt(III) complexes as catalysts of asymmetric synthesis of cyanohydrins
作者:Yu. N. Belokon’、V. I. Maleev、I. L. Mal’fanov、T. F. Savel’eva、N. S. Ikonnikov、A. G. Bulychev、D. L. Usanov、D. A. Kataev、M. North
DOI:10.1007/s11172-006-0338-4
日期:2006.5
Chiral coordinatively saturated cobalt(III) complexes with Schiff bases of enantio-pure amino acids are formed as Λ and Δ-isomers, which are not transformed into each other under normal conditions. These complexes catalyze the formation of enantiomerically enriched cyanohydrins from aldehydes and Me3SiCN under homo-and heterogeneous catalysis.
Two‐in‐one: The integration of two salen/TiO units into one molecule allows the enantioselectivecyanation of aldehydes to afford the enantioenriched natural or nonnatural cyanohydrin derivatives with turnover numbers of 1960–172 000 and ee values up to 97 % (see scheme). Some of the cyanohydrin derivatives are key intermediates for the synthesis of chiral pharmaceuticals or agrochemicals.
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 enantioselective addition of trimethylsilyl cyanide to a variety of aldehydes proceeded by the aid of a catalyst prepared in situ from titanium tetraisopropoxide [Ti(O-i-Pr)4] and chiral Schiff bases and gave the corresponding cyanohydrins in high optical yield (up to 96% e.e.). A remarkable rate enhancement was brought about by the addition of the Schiffbase to the titanium alkoxide mediated
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。