Formation of Hindered Arylcarbamates using Alkyl Aryl Carbonates under Highly Reactive Conditions.

Hindered O-tert-alkyl N-arylcarbamates were conveniently prepared by treating arylamines with aryl tert-alkyl carbonates in the presence of a strong base. The new method avoids the use of sensitive and difficult-to-access dialkyl dicarbonates and isocyanates, which are most commonly used in known methods. Instead, the stable and readily accessible alkyl aryl carbonates are used. Therefore, the new method is particularly suitable for the synthesis of N-arylcarbamates that contain a complex O-alkyl moiety. Using the method, electron-rich and electron-poor, and primary and secondary arylamines can all be conveniently converted to their carbamates with acceptable yields. The method was also found equally effective for the synthesis of the less hindered O-secondary and O-primary alkyl N-arylcarbamates.