Synthesis of Multifunctional 3-Amino-4-phosphono-2-quinolinones via Regioselective Ring Enlargement of Imino Isatins

Multifunctional 3-amino-4-dialkylphosphono-2-quinolinones have been prepared by onepot nucleophilic addition and regioselective ring enlargement of imino isatins. The addition reaction between imino isatins and dialkyl (diazomethyl)phosphonate proceeds smoothly using potassium carbonate as a catalyst, and a subsequent regioselective ring expansion promotes by salicylic acid to afford the desired products in high yields.