Table 1. Selected Optimization Results for the Mn- and Co-Catalyzed Cyclizations.

^aDetermined by ¹H NMR spectroscopy with 1,3,5-trimethoxybenzene as the internal standard.

^bIsolated yield.

^cAir was continuously introduced into the reaction mixture.

^dThe reaction was conducted at 25 °C for 12 h.

^eThe reaction was conducted at 25 °C for 1 h.