Palladium-Catalyzed, Enantioselective Formal Cycloaddition between Benzyltriflamides and Allenes: Straightforward Access to Enantioenriched Isoquinolines
摘要:
Benzyl and allyltriflamides can engage in Pd-catalyzed oxidative (4+2) annulations with allenes, to produce highly valuable tetrahydroisoquinoline or dihydropyridine skeletons. The reaction is especially efficient when carried out in the presence of designed N-protected amino acids as metal ligands. More importantly, using this type of chiral ligands, it is possible to perform desymmetrizing, annulative C-H activations of prochiral diarylmethylphenyl amides, and thus obtain the corresponding isoquinolines with high enantiomeric ratios.
A Role for Pd(IV) in Catalytic Enantioselective C–H Functionalization with Monoprotected Amino Acid Ligands under Mild Conditions
作者:R. Erik Plata、David E. Hill、Brandon E. Haines、Djamaladdin G. Musaev、Ling Chu、David P. Hickey、Matthew S. Sigman、Jin-Quan Yu、Donna G. Blackmond
DOI:10.1021/jacs.7b03716
日期:2017.7.12
Kinetic and mechanisticstudies of the desymmetrization of benzhydrylamine using Pd/monoprotected amino acid ligands (Pd/MPAA) via C–H functionalization with moleculariodine provide mechanistic insight into the rate-determining step and the oxidation state of Pd in the C–H functionalization step. Enantiomeric excess is strikingly insensitive to temperature from ambient temperature up to over 70 °C
使用Pd /单保护的氨基酸配体(Pd / MPAA)通过CH-H官能化和分子碘对苯甲基胺脱对称化的动力学和机理研究,提供了对C-H官能化过程中Pd的速率决定步骤和氧化态的机械理解。步。对映体过量对环境温度至最高70°C的温度极不敏感,反应速率对配体苯甲酰基保护基团的电子特性不敏感。该反应高度稳健,没有催化剂失活的迹象。有趣的是,在向反应混合物中添加I 2之前,不会发生C–H键断裂。电化学实验证明了I 2氧化加成Pd(II)的可行性。和...一起在19 F NMR研究中,这些观察结果表明,碘在添加胺底物之前会氧化Pd。这项工作可能会导致人们对C–H官能化反应的反应机理的细微变化有更好的一般性理解,具体取决于底物,氨基酸配体和保护基团以及反应条件,这种配体类别可能存在。
Palladium-Catalyzed, Enantioselective Formal Cycloaddition between Benzyltriflamides and Allenes: Straightforward Access to Enantioenriched Isoquinolines
作者:Xandro Vidal、José L. Mascareñas、Moisés Gulías
DOI:10.1021/jacs.8b12636
日期:2019.2.6
Benzyl and allyltriflamides can engage in Pd-catalyzed oxidative (4+2) annulations with allenes, to produce highly valuable tetrahydroisoquinoline or dihydropyridine skeletons. The reaction is especially efficient when carried out in the presence of designed N-protected amino acids as metal ligands. More importantly, using this type of chiral ligands, it is possible to perform desymmetrizing, annulative C-H activations of prochiral diarylmethylphenyl amides, and thus obtain the corresponding isoquinolines with high enantiomeric ratios.
Dynamic Ligand Exchange as a Mechanistic Probe in Pd-Catalyzed Enantioselective C–H Functionalization Reactions Using Monoprotected Amino Acid Ligands
作者:David E. Hill、Katherine L. Bay、Yun-Fang Yang、R. Erik Plata、Ryosuke Takise、K. N. Houk、Jin-Quan Yu、Donna G. Blackmond
DOI:10.1021/jacs.7b11962
日期:2017.12.27
A new tool for probing enantioselective reaction mechanisms is introduced. Monitoring the temporal change in product enantiomeric excess after addition of the opposite enantiomer of the ligand during the reaction provides a means of probing dynamic ligand exchange in enantioselective C-H iodination catalyzed by Pd with monoprotected amino acid ligands (MPAAs). This work has general potential to provide