Dual rhodium/copper catalysis: synthesis of benzo[b]fluorenes and 2-naphthalenylmethanones via de-diazotized cycloadditions

A novel synergistic rhodium/copper catalysis has been established, enabling de-diazotized cycloadditions of 1,5-enynes and alpha-diazocarbonyls toward the selective formation of densely functionalized benzo[b] fluorenes and 2-naphthalenylmethanones. alpha-Aryldiazoesters result in the formation of triple C-C bonds through bimetallic catalysis whereas a range of functionalized naphthalenes with a 1,5-dicarbonyl unit were accomplished using alpha-diazocarbonyls without any substituent at the alpha-position, indicating that substituents at the alpha-position of the alpha-diazocarbonyl unit could control the selectivity of the reaction.