Fig. 9

Iron-catalyzed reductive N-methylation^a. a Reaction pathway showing stepwise reductive methylation of nitro compounds. b ¹³C-Labeled experiment showing paraformaldehyde as C1 source^{i, ii, iii}. Reaction conditions: ⁱ0.5 mmol of 5-nitrobenzimidazole, 10 mmol of ¹³C-labeled paraformaldehyde (300 mg), 50 mg Fe₂O₃/NGr@C (5 mol% Fe), 1 mmol Na₂CO₃ (106 mg), 2 mL DMSO-water (1:1), 130 °C, 24 h. ⁱⁱ0.5 mmol of 1, 10 mmol paraformaldehyde (300 mg), 50 mg Fe₂O₃/NGr@C (5 mol% Fe), 1 mmol Na₂CO₃ (106 mg), 2 mL DMSO-water (1:1), 130 °C, 24 h. ⁱⁱⁱ0.5 mmol of 1, 50 bar H₂, 50 mg Fe₂O₃/NGr@C (5 mol% Fe), 1 mmol Na₂CO₃ (106 mg), 2 mL DMSO-water (1:1), 130 °C, 24 h. All are isolated yields