An efficient and mild protocol for the synthesis of unsymmetrical ureas in the absence of catalyst and additives

Synthesis of Unsymmetrical Ureas andS-Thiocarbamates under Catalyst-free Conditions in a [BMIM]BF4Ionic Liquid

“…This could be probably due to the acidity of the media which can deactivate the amine nucleophile by protonation leading to formation of aniline. However, we have previously reported that, when p ‐nitroaniline was applied as a nucleophile in this reaction, the same results were observed due to the weak nucleophilicity of the amine .…”

“…The main advantage of this method is in situ formation of phenyl isocynate in the reaction media, instead of using it as a starting precursor, as we previously reported in the synthesis of unsymmetrical ureas from phenylurea and amines under the refluxing temperature of dioxane .…”

Acyclic and Cyclic Ureas (Update 2013)

“…Examples are reaction of urea with amines by using iodine, [87] zinc(II) chloride, [88] or catalytic amounts of cerium(III) chloride hexahydrate/potassium iodide and microwave irradiation, [89] or under thermal conditions. [90] 1-Ethyl-3-phenylurea (26,Ar 1 =Ph); Typical Procedure: [86] In a 25-mL Schlenk tube equipped with a magnetic stirrer bar, Cu(OAc) 2 (18 mg, 0.1 mmol), ethylurea (88 mg, 1 mmol), PhNH 2 (121 mg, 1.3 mmol), and 2-methylbutan-2ol (2 mL) were added successively. The Schlenk tube was closed and the resulting mixture was stirred at 140 8 8C for 8 h under argon.…”

Synthesis of Complex Ureas with Brominated Heterocyclic Intermediates

“…[21][22][23][24] Hence, the development of greener and safer methodologies is essential for preparing these relevant molecules. [25][26][27][28][29][30][31][32][33] For this reason, as part of our ongoing efforts in the synthesis of biologically active heterocycles, we present a novel approach that uses simple ureas as building blocks to generate more complex derivatives. This procedure involves the reaction of 1-(3-(bromomethyl)-1-tosyl-1H-indol-2-yl) ketones 3 with simple ureas to prepare 1-((2-acyl-1-tosyl-1H-indol-3-yl)methyl) ureas 4 in good yields.…”

“…Hence, the development of greener and safer methodologies is essential for preparing these relevant molecules [25–33] . For this reason, as part of our ongoing efforts in the synthesis of biologically active heterocycles, we present a novel approach that uses simple ureas as building blocks to generate more complex derivatives.…”