Highly efficient synthesis of 1H-quinazoline-2,4-diones using carbon dioxide in the presence of catalytic amount of DBU

The first example of chemical fixation of carbon dioxide in the presence of catalytic amount of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or DBN (1,5-diazabicyclo[4.3.0]non-5-ene) was developed. Carbon dioxide easily reacted with 2-aminobenzonitriles under mild conditions (1 atm, 20 °C), assisted by excess amount of DBU or DBN to give corresponding 1H-quinazoline-2,4-diones in excellent yields. Also, catalytic amount of DBU or DBN is effective for the synthesis of 1H-quinazoline-2,4-diones. Using catalytic amount of DBU (0.05 equiv.), 7-chloro-1H-quinazoline-2,4-diones which is a key intermediate of medicines (FK366, Zenarestat® and KF31327) was synthesized successfully in a 90% yield under the CO2 pressure of 10 atm at 80°C.