Cobalt(I)-Catalyzed (3+2+2) Cycloaddition between Alkylidenecyclopropanes, Alkynes, and Alkenes

Cobalt(I) catalysts equipped with bisphosphine ligands can be used to promote formal (3 + 2 + 2) intramolecular cycloadditions of enynylidenecyclopropanes of type 1. The method provides synthetically appealing 5,7,5-fused tricyclic systems in good yields and with complete diastereo- and chemoselectivity. Interestingly, its scope differs from that of previously reported annulations based on precious metal catalysts, specifically rhodium and palladium. Noticeably, density functional theory calculations confirm that the mechanism of the reaction is also different from those proposed for these other catalysts.

Automated summary

This study investigates the application of cobalt(I) catalysts with bisphosphine ligands for promoting intramolecular cycloadditions of enynylidenecyclopropanes. The method successfully synthesizes 5,7,5-fused tricyclic systems with high yields and complete diastereo- and chemoselectivity. Interestingly, the scope and mechanism of this reaction differ from previously reported annulations using rhodium and palladium catalysts.