Anthranilic acid method
7 g of anthranilic acid, 5 ml of o-toluidine and 4 ml of glacial acetic acid were mixed in a round-bottom flask. 40-50 g of polyphosphoric acid was slowly added to this mixture, and the mixture was heated for 20-30 minutes to 140-160 ° C. After that, the mixture was heated to 180 ° C for 10 minutes, then cooled and poured into 150-200 ml of water and neutralized with a 20% solution of Na2CO3. Methanol was added until prolonged turbidity was observed in the solution, and after one hour methaqualone in the form of a free base precipitated, and once again recrystallized in this way. Yield 55%.