Selenium-Catalyzed Carbonylation to Phenylcarbamates and Methylene Diphenyl Dicarbamates

A clean, economical and efficient approach to phenylcarbamates and methylene diphenyl dicarbamates was reported. With cheap and easily available nonmetal selenium as the catalyst, carbon monoxide instead of virulent phosgene as the carbonylation reagent, oxygen as the oxidant, the selenium-catalyzed oxidative carbonylation reaction of aniline could proceed smoothly with alcohols to afford phenylcarbamates mostly in moderate to good yields. Then, catalyzed by HCl/ZnCl2, the condensation of formaldehyde with the generated phenylcarbamates gave methylene diphenyl dicarbamates in moderate to good yields. The applicability of the substrates was good. Catalyst selenium could be easily recovered due to its function of phase-transfer catalysis and could be recycled. High atomic economy, low cost, no emission of corrosive waste, and phosgene-free condition make this approach very promising. The possible reaction mechanisms were also proposed.