Cooperative Rh/Chiral Phosphoric Acid Catalysis toward the Highly Stereoselective (3+3)-Cycloannulation of Carbonyl Ylides and Indolyl-2-methides

A stereoselective (3 + 3)-cycloannulation of in situ generated carbonyl ylides with indolyl-2-methides has been developed furnishing oxa-bridged azepino[1,2-a]indoles within one synthetic step. This process is enabled by cooperative rhodium and chiral phosphoric acid catalysis to produce both transient intermediates in separate catalytic cycles. The products comprising three stereogenic centers were obtained with good stereoselectivity and yields and display valuable heterocyclic complexity.

Automated summary

A synthetic method has been developed for the stereoselective (3 + 3)-cycloannulation of in situ generated carbonyl ylides with indolyl-2-methides, resulting in oxa-bridged azepino[1,2-a]indoles in one step. The products, with three stereogenic centers, were obtained with good stereoselectivity and yields, showcasing valuable heterocyclic complexity.