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This paper reports a study of a green method of the common N-Boc protection of amines. It uses ultrasound irradiation because it doesn't require a reaction solvent, can have an excellent yield, and be performed in a short period of time at ambient temperature. This sonochemical study attempts to perform a process while adhering to green chemistry principles. After the experiment, the results showed that the energy from the ultrasound radiation--without any catalyst or reaction solvent--generate vibrations within the reactants, facilitating the N-Boc protection of amine in the reaction. The researchers concluded that this procedure was easier and more efficient than traditional methods of N-Boc protection because it is environmentally friendly, finished in a shorter amount of time, performed under conditions without a solvent, and doesn't generate byproducts. Additionally, this paper references our original paper when it mentions Amberlyst-15 as a catalyst used in Lewis-acid catalyzed reactions for N-boc protection.

In this paper, researchers attempt to reproduce the results an earlier paper reported about a procedure for chemoselective mono-N-Boc protection of amino acids, amines, and peptides with a di-tert-butyl decarbonate. The reaction was catalyzed with Amberlyst-5 catalyst in ethanol, which can be used for both N-boc protection and deprotection. This experiment involved reacting aniline with 1.1 equiv (Boc)2O with the Amberlyst-15 catalyst present at room temperature. Protic solvents were found to be most effective, particularly ethanol, so it was used as the reaction solvent and generated a respectable yield. A solvent-free reaction was also done to test an earlier report that said this reaction would finish within 1-12 minutes, but results were not consistent with it because the time and experimental yield did not match it. In the reaction with ethanol solvent, no impurities, such as urea or N,N-di-Boc derivatives, were detected from TLC and H1 NMR analyses—a good result. Amines reacted well to give outstanding yields of N-boc products. The researchers concluded that this procedure, taking place at room temperature in ethanol solvent with easily recoverable Amberlyst-5 catalyst, is an efficient procedure for N-tert-butoxycarbonylation of various types of amines.