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
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
An Asymmetric Michael Addition of α,α-Disubstituted Aldehydes to Maleimides Leading to a One-Pot Enantioselective Synthesis of Lactones Catalyzed by Amino Acids
作者:Christoforos G. Kokotos
DOI:10.1021/ol4008662
日期:2013.5.17
A cheap and fast construction of both enantiomers of substituted succinimides is reported. α- or β-amino acids, such as β-phenylalanine and α-tert-butyl aspartate, were found to be efficient organocatalysts for the reaction between α,α-disubstituted aldehydes and maleimides. Products containing contiguous quaternary-tertiary stereogenic centers are obtained in high to quantitative yields and excellent
amine-salicylamide derived from chiral trans-cyclohexane-1,2-diamine was used as an organocatalyst for the enantioselective conjugate addition of aldehydes, mainly α,α-disubstituted to N-substituted maleimides. The reaction was performed in toluene as a solvent at room temperature. The corresponding enantioenriched adducts were obtained with high yields and enantioselectivities up to 94%. Theoretical calculations
Michael Addition of Ketones and Aldehydes to Maleimides Catalyzed by Modularly Designed Organocatalysts
作者:Savitha Muramulla、Jun-An Ma、John Cong-Gui Zhao
DOI:10.1002/adsc.201300041
日期:2013.5.3
primary α‐amino acids and Cinchona alkaloid thioureas were found to be excellent catalysts for the stereoselective Michaeladdition of enolizable ketones and aldehydes to maleimides. Using an MDO formed from quinidine thiourea and L‐2‐chlorophenylglycine, the corresponding Michaeladdition products, 3‐substituted succinimides, may be obtained in excellent yields and high enantio‐ and diastereoselectivities