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
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
reagents to α,β-unsaturated carbonyls is a key strategy for the construction of carbon-carbon bond in organic synthesis. Although direct C-H addition to unsaturated bonds via transition metal catalysis is explored in recent years, electron-deficient arenes that do not bear directing groups continue to be challenging. Herein we disclose the first example of a conjugate addition of perfluoroarenes to α,β-unsaturated
Enantioselective organocatalytic substitution of α-cyanoacetates on imidoyl chlorides – synthesis of optically active ketimines
作者:Stefano Santoro、Thomas B. Poulsen、Karl Anker Jørgensen
DOI:10.1039/b715810f
日期:——
The enantioselective substitution of α-cyanoacetates on imidoyl chlorides under phase-transfer catalytic conditions is presented; a simple quinidine-derived phase-transfer catalyst gives access to the products, highly substituted ketimines, in generally good yields and up to 90% ee.
Phosphine-catalyzed regioselective Michael addition to allenoates
作者:Vasudeva Rao Gandi、Yixin Lu
DOI:10.1039/c5cc06197k
日期:——
The first phosphine catalysed Michael addition of arylcyanoacetates to allenoates has been developed, and the β-selective products with a quaternary center were obtained in excellent yields.