One-Pot Synthesis of 1,4-Dihydro-2-thioxo-2H-3,1-benzoxazine-4-acetic Acid Derivatives by the Reaction of 2-Isothiocyanatophenyl Ketones with Lithium Enolates of Acetates and Tertiary Acetamides

The one-pot synthesis of 4-aryl-1,4-dihydro-2-thioxo-2H-3,1-benzoxazine-4-acetic acid derivatives 2 was achieved in good yields by the reaction of aryl(2-isothiocyanatophenyl)methanones 1 with lithium enolates of acetates and tertiary acetamides. (2E)-1-(2-Isothiocyanatophenyl)-3-phenylprop-2-en-1-one (3) gave 1,4-dihydro-4-[(1E)-2-phenylethenyl]-2-thioxo-2H-3,1-benzoxazine-4-acetic acid derivatives 4 in good yields as well.