The synthesis of hydroxamic acids starting from carboxylic acids
employing 1-propanephosphonic acid cyclic anhydride (T3P) activation
is described. Application of ultrasonication accelerates this conversion.
Further, the T3P has also been employed to activate the hydroxamates,
leading to isocyanates via the Lossen rearrangement. The isocyanates
were trapped with suitable nucleophiles to afford the corresponding
ureas and carbamates.
T3P - hydroxamic acids - Lossen rearrangement - isocyanates