Gold‐Catalyzed [3+2]‐Annulations of α‐Aryl Diazoketones with the Tetrasubstituted Alkenes of Cyclopentadienes: High Stereoselectivity and Enantioselectivity

• Published in: Angewandte Chemie Vol. 133; no. 9; pp. 4529 - 4534
• Main Authors: Chen, Ching‐Nung, Cheng, Wei‐Min, Wang, Jian‐Kai, Chao, Tzu‐Hsuan, Cheng, Mu‐Jeng, Liu, Rai‐Shung
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 23.02.2021
• Subjects: [3+2]-annulations; Alkenes; Aromatic compounds; Carbenes; Carbonyl compounds; Carbonyls; Chemistry; Cloke–Wilson rearrangement; Cyclopentadiene; Enantiomers; Gold; gold catalysis; Ketones; Nucleophiles; Phosphates; Phosphoric acid; Stereoselectivity; Substitutes; tetrasubstituted alkenes; α-diazo ketones
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202012611

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 forms of gold and phosphoric acid. Our mechanistic analysis supports that cyclopentadienes serve as nucleophiles to attack gold carbenes at the more substituted alkenes, yielding gold enolates that complex with chiral phosphoric acid to enhance the enantioselectivity. Enantioselective gold‐catalyzed [3+2]annulations between highly substituted cyclopentadienes and α‐diazo ketones yielded gold enolate intermediates. These form complex pairs with chiral phosphoric acid to enhance the enantioselectivity.