Light-sensitive protecting groups for amines and alcohols: The photosolvolysis of n-substituted 7-nitroindolines

Representative examples of primary and secondary amines were protected as urea derivatives 4 of 5-bromo-7-nitroindoline and even more efficiently as ureas 8 derived from 5,7-dinitroindoline, via high-yield reactions with carbamoyl chlorides 3 and 7, respectively. Deprotection of 4 or 8 was achieved in high yields by UV irradiation at room temperature in Pyrex vessels under neutral conditions and exclusion of air. In a similar manner the dinitroindolines serve as protecting groups for alcohols and phenols; the derived carbamates 5 and 9 can likewise be deprotected photochemically in high yields.