An Efficient Solid-Phase Synthesis of Ureas

Significance

An efficient and simple solid-phase synthesis of ureas was described. Thus, treatment of carboxylic acids 1 with diphenyl phosphoryl azide (DPPA) in the presence of triethylamine at r.t., followed by addition of silica-bound thiol 2 and heating overnight gave the silica-bound thiocarbamate 3. The resulting thiocarbamate 3 reacted with amines 4 in acetonitrile to release the corresponding ureas 5 from the silica support in 45-98% yield.