| Developing protocol to ureas has been one of the hot topics in organic synthesisdue to its importance in pharmaceuticals, bio-active molecules and functionalmaterials. Therefore, an efficient method to construct such a skeleton has been ofsignificance in practical applications. In this thesis, two convenient methods tosynthesize ureas by aid of carbamate Boc2O have been established. The main resultsobtained are as follows：1)We have applied the microwave technique in the synthesis of urea under metalor organic catalyst free conditions. In this transformation, carbonyl group of Boc wasretained into the urea molecule, avoiding the deprotection step. This method featureswith being of rapid, efficient, simple, atom-economic and green procedure. N-Boc ofan aromatic amine （1.0eq.） and an excess of the amine were added in the microwavereaction tube. The reaction was run at150oC for45-75min. Then unasymmetric ureawas given in good to excellent yield. The pure product was obtained by simplywashing with a small amount of petroleum ether.2)A facial and efficient one-pot strategy for synthesis of symmetric andunsymmetric ureas from amines and Boc2O by aid of bases under the metal-free andsolvent-free conditions has been developed. Sodium t-butoxide exhibited the highestreactivity. The mixture of Boc2O （1.0eq.） and an excess of amine was stirred at roomtemperature for0.5h, affording N-Boc aromatic amines. Then sodium tert-butanol（1.1eq.） was added. The reaction was heated for several hours, and symmetrical ureaderivatives were obtained in the one-pot. The mixture of aryl amine （1.0eq.） andBoc2O （1.05eq.） was stirred at room temperature or heating conditions, and gave theN-Boc aryl amine. Sodium t-butanol （1.1eq.） and an excess of aliphatic amines（primary, secondary, a cyclic or heterocyclic amine） was added, affording asymmetricurea derivatives after refluxing for several hours. The excess of the amines playeddual roles as a reagent and solvent in this transformation. |
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