A very simple, efficient, and regiospecific protocol for aminobromination of a wide scope of beta-nitrostyrene derivatives with N-bromoacetamide (NBA) as nitrogen/bromine sources has been developed by using K(3)PO(4) as catalyst. The reaction proceeded smoothly and cleanly to give the bromoamines in good to excellent yields (78-99%) within 24 h in CH(2)Cl(2) at room temperature without protection of inert gases. A possible mechanism involving a nucleophilic conjugate addition was proposed.
The regio- and stereoselective aminobromination of alpha,beta-unsaturated ketones catalyzed by copper powder has been established with 4-TsNH(2) and NBS as the nitrogen/bromine sources, respectively. This method provides an easy access for preparation of vicinal aminohalo derivatives in the presence of 1 mol % catalyst. Electron-rich alpha,beta-unsaturated ketones afforded the corresponding aminobrominated products in excellent yields (up to 99.8%), revealing that the addition has an electrophilic feature.
The silver salt catalyzed [3+2] cycloaddition reaction of trifluoromethylated N-acylhydrazones and ethyl isocyanoacetate was investigated. The reaction proceeds quickly to produce a series of trifluoromethylated 2-imidazoline compounds in high yields with excellent stereoselectivity, which provides a novel and efficient method for the synthesis of trifluoromethylated 2-imidazoline compounds.
As novel and efficient difluoromethyl
building blocks, difluoroacetohydrazonoyl
bromides have been synthesized for the first time. The synthetic utility
of this reagent for the construction of difluoromethyl organic compounds
is demonstrated by their effective regioselective [3 + 2] cycloaddition
reactions with ynones, alkynoates, and ynamides. The reactions provide
a novel and efficient protocol to access difluoromethyl-substituted
pyrazoles in good to excellent yields.
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