Asymmetric [4+2] Annulation of C1 Ammonium Enolates with Copper‐Allenylidenes

• Published in: Angewandte Chemie International Edition Vol. 56; no. 19; pp. 5212 - 5216
• Main Authors: Song, Jin, Zhang, Zi‐Jing, Gong, Liu‐Zhu
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 02.05.2017; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: [4+2] annulations; C1 ammonium enolates; Chemistry; Chemistry, Multidisciplinary; cooperative catalysis; copper; heterocycles; Physical Sciences; Science & Technology; ORGANIC-SYNTHESIS; SUBSTITUTION; METAL-CATALYSTS; C1 ammonium enolates; cooperative catalysis; [4+2] annulations; ACETIC-ACID ESTERS; ALCOHOLS; CYCLOADDITION; heterocycles; BETA-LACTONES; copper; ENANTIOSELECTIVE PROPARGYLIC ALKYLATION; SELECTIVE SYNTHESIS
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201700105

An asymmetric catalytic decarboxylative [4+2] annulation of 4‐ethynyl dihydrobenzooxazinones and carboxylic acids has been established by cooperative copper and nucleophilic Lewis base catalysis. A C1 ammonium enolate and copper–allenylidene complex, each catalytically generated from different substrates, underwent a cascade asymmetric propargylation and lactamization process to yield optically active 3,4‐dihydroquinolin‐2‐one derivatives with excellent levels of stereoselectivity (up to 99 % ee, 95:5 d.r.). A team effort: An asymmetric [4+2] annulation of C1 ammonium enolates with copper–allenylidenes catalytically generated from carboxylic acids and 4‐ethynyl dihydrobenzooxazinones, respectively, led to optically active 3,4‐dihydroquinolin‐2‐one derivatives with excellent levels of stereoselectivity.