Achieving Site Selectivity in Metal-Catalyzed Electron-Rich Carbene Transfer Reactions from N-Tosylhydrazones.

Catalyst control of the site-selectivity of electron-rich alkyl, aryl disubstituted carbenes generated in situ from o-alkenyl-substituted N-tosylhydrazones was achieved in this study. Exposure of these substrates to copper iodide triggered the formation of α-alkoxy 2H-naphthalenones. This investigation established that changing the catalyst to a rhodium(II) carboxylate turned off cyclization and migration of the electron-rich metal carbene with the β-carboxylate and turned on allylic C-H bond functionalization to diastereoselectively afford 1H-indenes. Examination of the scope of this reaction revealed that ethereal, aminomethylene, and unactivated 2° C-H bonds could be functionalized.