Enantioselective Construction of Tetrasubstituted Stereogenic Carbons through Brønsted Base Catalyzed Michael Reactions: α′-Hydroxy Enones as Key Enoate Equivalent
作者:Eider Badiola、Béla Fiser、Enrique Gómez-Bengoa、Antonia Mielgo、Iurre Olaizola、Iñaki Urruzuno、Jesús M. García、José M. Odriozola、Jesús Razkin、Mikel Oiarbide、Claudio Palomo
DOI:10.1021/ja510603w
日期:2014.12.24
tetrasubstituted carbon stereocenters in high diastereo- and enantioselectivity in the presence of standard BB catalysts. Experiments show that the α'-oxy ketone moiety plays a key role in the above realizations, as parallel reactions under identical conditions but using the parent α,β-unsaturated ketones or esters instead proceed sluggish and/or with poor stereoselectivity. A series of trivial chemical
催化和不对称迈克尔反应构成了合成中构建新 CC 键的非常强大的工具,但大多数声称具有高选择性的报告仅限于亲核/亲电化合物类型的某些特定组合,只有少数成功的方法处理了全碳四元立体中心。基于手性双功能 Brønsted 碱 (BB) 催化和使用 α'-氧烯酮作为使迈克尔受体具有矛盾的 H 键受体/供体特征,这是一种尚未报道的双齿烯酸设计元素,为解决这一差距做出了贡献。等价物。发现之前证明具有挑战性的一系列烯醇化羰基化合物(即 α-取代的 2-羟吲哚、氰基酯、恶唑酮、噻唑酮、和 azlactones) 到 α'-氧烯酮可以在标准 BB 催化剂存在下以高非对映选择性和对映选择性提供相应的四取代碳立体中心。实验表明,α'-氧基酮部分在上述实现中起着关键作用,因为在相同条件下进行平行反应,但使用母体 α,β-不饱和酮或酯进行缓慢和/或立体选择性差。对加合物中的酮醇部分进行一系列简单的化学操作可以在非常
New, Chiral Phase Transfer Catalysts for Effecting Asymmetric Conjugate Additions of α-Alkyl-α-cyanoacetates to Acetylenic Esters
作者:Xisheng Wang、Masanori Kitamura、Keiji Maruoka
DOI:10.1021/ja068119g
日期:2007.2.1
A new, chiral phasetransfercatalyst has been designed for the development of a general and useful procedure on the hitherto unknown, asymmetric conjugate additions of α-substituted-α-cyanoacetates to acetylenic esters with high enantioselectivity and moderate E/Z selectivity.
Palladium-Catalyzed CH Activation of N-Allyl Imines: Regioselective Allylic Alkylations to Deliver Substituted Aza-1,3-Dienes
作者:Barry M. Trost、Subham Mahapatra、Martin Hansen
DOI:10.1002/anie.201501322
日期:2015.5.11
mode of activation of an imine via a rare aza‐substituted π‐allyl complex is described. Palladium‐catalyzed C(sp3)H activation of the N‐allyl imine and the subsequent nucleophilic attack by the α‐alkyl cyanoester produced the 1‐aza‐1,3‐diene as the sole regioisomer. In contrast, nucleophilic attack by the α‐aryl cyanoester exclusively delivered the 2‐aza‐1,3‐diene, which was employed in an inverse‐electron‐demand
An Air‐ and Water‐Stable Hydrogen‐Bond‐Donor Catalyst for the Enantioselective Generation of Quaternary Carbon Stereocenters by Additions of Substituted Cyanoacetate Esters to Acetylenic Esters
作者:Quang H. Luu、John A. Gladysz
DOI:10.1002/chem.202001639
日期:2020.8.12
is trans to the new carbon–carbon bond dominate (avg. ratio 98:2). These are obtained in 70–98 % ee (avg. 86 %; data for optimum R′ and R′′′), as determined by 1H NMR with the chiralsolvatingagent Λ‐(S ,S )‐2 3+ 2I−B(3,5‐C6H3(CF3)2)4−. NMR experiments show that the cyanoacetate and acetylenic esters and pyridine can hydrogen bond to certain NH groups of the catalyst. Rates are zero order in the cyanoacetate
Catalytic Asymmetric Alkylation of α-Cyanocarboxylates Using a Phase-Transfer Catalyst
作者:Takashi Itoh、Kazuhiro Nagata、Daisuke Sano
DOI:10.1055/s-2007-967963
日期:——
The highly enantioselective catalytic alkylation of cyanoacetates was achieved using a chiralphase-transfercatalyst to give α,α-disubstituted α-cyanoacetates which have a chiral quaternary carbon. The product thus obtained was applied to the synthesis of an opticallyactive oxindole.