In the process of producing an aromatic polyisocyanate from a methylated benzene compound having the sequential steps of ammoxidation, hydrolysis, conversion of amide to carbamate, condensation and conversion of polycarbamate ester to polyisocyanate, the improvement of converting said amide to said carbamate in a one-step reaction wherein said amide is reacted with an N-halogenating agent in the presence of alcohol and in a reaction medium having a pH of from neutral to basic and a temperature greater than 40.degree. C.