Synthesis and evaluation of guanidinyl pyrrolidines as bifunctional catalysts for enantioselective conjugate additions to cyclic enones
作者:Sunil V. Pansare、Rajinikanth Lingampally
DOI:10.1039/b812038b
日期:——
Guanidinyl pyrrolidines derived from ‘S’-proline are effective catalysts for the enantioselective conjugate addition of malonate, nitroalkane and other carbon and heteroatom nucleophiles to cyclohexenone and cyclopentenone in the absence of basic additives. The stereoselectivity is strongly dependant on catalyst loading as well as reaction concentration.
衍生自“ S ”-脯氨酸的胍基吡咯烷是将丙二酸酯,硝基烷和其他碳原子和杂原子亲核试剂对映选择性共轭加成的有效催化剂。环己烯酮 和 环戊烯酮在没有碱性添加剂的情况下。立体选择性很大程度上取决于催化剂的负载以及反应浓度。
Asymmetric ruthenium-catalyzed 1,4-additions of aryl thiols to enones
作者:Andrei Bădoiu、Gerald Bernardinelli、Céline Besnard、E. Peter Kündig
DOI:10.1039/b918877k
日期:——
bind and activate α,β-unsaturated carbonyl compounds for cycloadditionreactions. These mild Lewisacidscatalyzeasymmetric 1,4-addition reactions of aryl thiols to enones with product selectivities up to 87% ee. 31P NMR experiments provide an insight into the intricate equilibria governing the reaction mechanism. The absolute configuration of the major products indicates enones to react in the syn-s-trans
定义明确,稳定的单点绑定 钌配合物1和2选择性地结合并活化α,β-不饱和羰基化合物以进行环加成反应。这些温和的路易斯酸催化芳基硫醇与烯酮的不对称1,4-加成反应,产物选择性高达ee的87%。31 P NMR实验提供了控制反应机理的复杂平衡的见解。主要产品的绝对构型表示烯酮的反应合成- S ^ -反式方向。基于Ru配合物的X射线结构的模型可用于合理化选择性。
Synthesis and Resolution of a Multifunctional Inherently Chiral Calix[4]arene with an ABCD Substitution Pattern at the Wide Rim: The Effect of a Multifunctional Structure in the Organocatalyst on Enantioselectivity in Asymmetric Reactions
synthetic route to inherentlychiralcalix[4]arenes with an ABCD substitution pattern at the wide rim in the coneconformation was developed for the first time. For the synthesis of inherentlychiral ABCD-type calix[4]arenes, first 5,11-dibromo-17-(3,5-dimethylphenyl)-25,26,27,28-tetrapropoxycalix[4]arene (9) was prepared as a key intermediate. Then, functionalization of the calix[4]arene 9 was examined
Bifunctional chiral organocatalysts comprising thiourea and tertiaryamine groups were synthesized. They act as efficientcatalysts for asymmetric Michaeladdition of arylthiols to alpha,beta-unsaturated carbonyl compounds. Enantioselectivity up to 85% has been achieved. Asymmetric alpha-protonation reaction (up to 60% ee) can be obtained in the presence of the bifunctionalcatalyst.
Improved design of inherently chiral calix[4]arenes as organocatalysts
作者:Seiji Shirakawa、Shoichi Shimizu
DOI:10.1039/b9nj00685k
日期:——
design of inherentlychiralcalix[4]arenes as organocatalysts was accomplished via the introduction of a diarylmethanol structure. Novel, inherentlychiralcalix[4]arenes bearing a tertiary amine or a quaternary ammonium moiety, together with a diarylmethanol moiety, were synthesized from previously reported chiralcalix[4]arene amino acid derivatives in an optically pure form. These chiralcalix[4]arenes