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

This work reports gold-catalyzed [3+2]-annulations of alpha-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 alpha-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.

Automated summary

This study demonstrates gold-catalyzed [3+2]-annulations of alpha-diazo ketones with highly substituted cyclopentadienes, resulting in bicyclic 2,3-dihydrofurans with high regio- and stereoselectivity. Enantioselective annulations can also be achieved using chiral forms of gold and phosphoric acid. The mechanistic analysis suggests that cyclopentadienes act as nucleophiles attacking gold carbenes, leading to gold enolates that complex with chiral phosphoric acid to enhance enantioselectivity.