A practically simple, mild and efficient method is developed for the synthesis of N-substituted ureas by nucleophilic addition of amines to potassium isocyanate in water without organic co-solvent. Using this methodology, a variety of N-substituted ureas (mono-, di-and cyclic-) were synthesized in good to excellent yields with high chemical purity by applying simple filtration or routine extraction procedures avoiding silica gel purification. The developed methodology was also found to be suitable for gram scale synthesis of molecules having commercial application in large volumes. The identified reaction conditions were found to promote a unique substrate selectivity from a mixture of two amines.
A facile, two-pot conversion of carboxylic acids into the corresponding nitriles has been developed using triflic anhydride as a promoter and aqueous NH4OH as a source of nitrogen. The methodology involves synthesis of primary amides from carboxylic acids as the key first step using triflic anhydride and aqueous NH4OH as a source of nitrogen. Triflic anhydride is also found to be an excellent reagent for conversion of primary amides into nitriles, affording high yields with considerable chemoselectivity and functional group tolerance. In spite of the mild reaction conditions and broad substrate scope for the two-step conversions, all attempts for one-pot domino conversion of acids into nitriles exhibited limited success because of poor yields.
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