Nonracemic ethano-bridged Tröger bases are prepared using CuTC-catalyzed decompositions of diazo compounds. Excellent levels of diastereo- and enantio-control (dr and ee up to 12 : 1 and 95% respectively) are now obtained with aryl diazoketone precursors.
Gold‐Catalyzed [3+2]‐Annulations of α‐Aryl Diazoketones with the Tetrasubstituted Alkenes of Cyclopentadienes: High Stereoselectivity and Enantioselectivity
作者:Ching‐Nung Chen、Wei‐Min Cheng、Jian‐Kai Wang、Tzu‐Hsuan Chao、Mu‐Jeng Cheng、Rai‐Shung Liu
DOI:10.1002/anie.202012611
日期:2021.2.23
This work reports gold‐catalyzed [3+2]‐annulations of α‐diazo ketones with highly substituted cyclopentadienes, affording bicyclic 2,3‐dihydrofurans with high regio‐ and stereoselectivity. The reactions highlights the first success of tetrasubstituted alkenes to undergo [3+2]‐annulations with α‐diazo carbonyls. The enantioselective annulations are also achieved with high enantioselectivity using chiral
Phosphine‐Catalyzed Activation of Alkylidenecyclopropanes: Rearrangement to Form Polysubstituted Furans and Dienones
作者:Xin He、Yuhai Tang、Yongzhuang Wang、Jian‐Bo Chen、Silong Xu、Jianwei Dou、Yang Li
DOI:10.1002/anie.201903320
日期:2019.7.29
We report a phosphine‐catalyzed ring opening of electron‐deficient alkylidenecyclopropanes (ACPs) to generate allylic phosphonium zwitterions that resemble the well‐studied phosphine‐allene adducts but exhibit distinct properties. The potent reactivity of these intermediates has been demonstrated in three types of substrate‐controlled phosphine‐catalyzed rearrangements of alkylidenecyclopropylketones
Construction of All-Carbon Quaternary Stereocenters via Sequential Photoactivation/Isothiourea Catalysis
作者:Tao Fan、Zi-Jing Zhang、Yu-Chen Zhang、Jin Song
DOI:10.1021/acs.orglett.9b02892
日期:2019.10.4
Highly enantioselective [4 + 2] cyclizations of azadienes with in situ generated ketenes were developed through sequential visible-light photoactivation/isothiourea catalysis, which offers a novel approach for the creation of all-carbonquaternarystereocenters through disubstituted C1-ammonium enolates. The visible-light-induced sustained release of reactive ketene species through Wolff rearrangement
Rh(II)/Brønsted Acid Catalyzed General and Highly Diastereo- and Enantioselective Propargylation of <i>in Situ</i> Generated Oxonium Ylides and C-Alkynyl N-Boc N,O-Acetals: Synthesis of Polyfunctional Propargylamines
The first metal/organo cooperatively catalyzed asymmetric reaction of C-alkynyl N-Boc-protected N,O-acetals with in situ generated oxonium ylides has been developed. This new type of propargylation allows for the efficient synthesis of structurally diverse unreported chiral propargylamines bearing oxa-quaternary stereocenters. The reaction features unprecedented substrate scope and high diastereo-