corresponding succinimides in good yields and enantioselectivities. DFT calculations support the stereochemical results and the role played by the solvents. Chiralprimary amines containing the (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine scaffold and a pyrimidin-2-yl unit are synthesized and used as general organocatalysts for the Michael reaction of α-branched aldehydes to maleimides. The reaction
N-Primary-amine tetrapeptide-catalyzed highly asymmetric Michael addition of aliphatic aldehydes to maleimides
作者:Zhi-Hong Du、Wen-Juan Qin、Bao-Xiu Tao、Meng Yuan、Chao-Shan Da
DOI:10.1039/d0ob01457e
日期:——
highly asymmetric Michaeladdition reaction between maleimides and aliphatic aldehydes catalyzed by low-loading β-turn tetrapeptides with excellent yields and enantioselectivities at room temperature was reported. α-Branched and α-unbranched aldehydes both are suitable nucleophiles. N-Aryl, alkyl and hydrogen maleimides all are well tolerated and led to high yields and enantioselectivities. The transformation
Chitosan as a chiral ligand and organocatalyst: preparation conditions–property–catalytic performance relationships
作者:Vanessza Judit Kolcsár、György Szőllősi
DOI:10.1039/d1cy01674a
日期:——
of natural origin. The effect of the preparation conditions by alkaline hydrolysis of chitin on the properties of chitosan was studied. The materials obtained were used as ligands in the ruthenium-catalysed asymmetric transfer hydrogenation of aromatic prochiral ketones and oxidative kinetic resolution of benzylic alcohols as well as organocatalysts in the Michael addition of isobutyraldehyde to N-substituted
壳聚糖是一种丰富且可再生的天然手性来源。研究了甲壳素碱水解制备条件对壳聚糖性质的影响。所得材料在钌催化的芳族前手性酮的不对称转移氢化和苄醇的氧化动力学拆分中用作配体,以及在异丁醛与N-取代的马来酰亚胺迈克尔加成中的有机催化剂。所制备材料的脱乙酰度由1H NMR、FT-IR 和 UV-vis 光谱、通过粘度测量获得的分子量、通过 WAXRD 获得的结晶度以及通过 SEM 和 TEM 研究获得的形态。材料还通过拉曼光谱表征。分子量在狭窄 (200-230 kDa) 范围内和适当 (80-95%) 脱乙酰度的生物聚合物是对映选择性转移氢化中最有效的配体,而在氧化动力学拆分中,配合物和立体选择性随着去乙酰化程度的增加而增加。壳聚糖的手性足以在异丁醛与水相中的马来酰亚胺迈克尔加成中获得对映选择。有趣的是,与单体D相比,生物聚合物提供了过量的相反对映体-氨基葡萄糖。在该反应中,发现脱乙酰度与催化活性之
Noncovalent Bifunctional Organocatalysts: Powerful Tools for Contiguous Quaternary-Tertiary Stereogenic Carbon Formation, Scope, and Origin of Enantioselectivity
作者:Thomas C. Nugent、Abdul Sadiq、Ahtaram Bibi、Thomas Heine、Lei Liu Zeonjuk、Nina Vankova、Bassem S. Bassil
DOI:10.1002/chem.201103005
日期:2012.3.26
observed. Using racemic α‐branched aldehydes, twocontiguous (quaternary–tertiary) stereogenic centers can be formed in high diastereo‐ and enantiomeric excess (eight examples) via an efficient in situ dynamic kinetic resolution, solving a known shortcoming for maleimide electrophiles in particular. The method is of practical value, requiring only 1.2 equiv of the aldehyde, a 5.0 mol % loading of each catalyst
依靠商业上可买到的催化剂构件的组装,已经实现了具有无与伦比的底物多样性的高度立体控制的季碳(所有碳取代的)形成。例如,三组分催化剂体系的原位组装允许将α-支链醛加成到硝基烯烃或马来酰亚胺亲电试剂中(Michael产品),而将α-支链醛加成可以得到曼尼希反应产物。观察到非常高的收率,在18个实例中,有15个实例的96-99%ee被观察到。使用外消旋的α-支链醛,可以通过高效的原位动态动力学拆分在高非对映异构体和对映体过量(八个实例)中形成两个连续的(四级-三级)立体中心,尤其是解决了已知的马来酰亚胺亲电试剂的缺点。该方法具有实用价值,仅需要1.2当量的醛,每种催化剂组分的负载量为5.0 mol%,例如O- t Bu- L-苏氨酸(O- t Bu- L- Thr),磺酰胺,DMAP或O-吨BU-大号-Thr,KOH,和室温下的反应。作为亮点,乙基异戊醛(7公开了添加),提供迄今已知的最拥挤的含
Highly enantioselective Michael addition of α,α-disubstituted aldehydes to maleimides catalyzed by new primary amine-squaramide bifunctional organocatalysts
作者:Zhi-wei Ma、Xiao-feng Liu、Jun-tao Liu、Zhi-jing Liu、Jing-chao Tao
DOI:10.1016/j.tetlet.2017.10.026
日期:2017.11
amine-squaramides catalyzed asymmetric Michael addition reaction of α,α-disubstituted aldehydes to maleimides has been developed. This organocatalytic asymmetric reaction provides easy access to functionalized succinimides with a broad substrate scope. Both enantiomers of desired succinimide derivatives were obtained in good to excellent yields (up to 98%) with excellent enantioselectivities (up to >99% ee)