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Efficient Iodine-catalyzed Synthesis of 3-Aryl 4(3H)-quinazolinones

Compounds with a 4-quinazolinone motif have displayed a variety of interesting pharmacological properties such as antimalarial, antitumor, anticonvulsant, antiinflammatory, fungicidal, antimicrobial and calcilytic activities.1–7 An examination of the literature indicates that 4-quinazolinones substituted at the 3-position are attracting the attention of chemists because they appear to have important sedative, hypnotic and anticonvulsive effects.8 There are several methods for the preparation of this class of compounds. The most direct procedure includes the condensation of anthranilic acid, ortho esters and amines in the presence of various catalysts such as NaHSO4 or Amberlyst-15,9 Yb(III)-resin,10 Yb(OTf)3, Bi(TFA)3-[nbp]FeCl4 ionic liquid,12 La(NO3)3·6H2O or p-toluenesulfonic acid,13 Keggin-type heteropolyacid,14 SnCl4·4H2O, and SiO2-FeCl3. While this type of multi-component reaction (MCR) can produce the desired products in a single step, some of these methods have certain drawbacks such as expensive catalysts, high temperatures (60–80◦C), long reaction times (20 h), and the use of harmful organic solvents. Most so-called “solvent-free” techniques still require an organic solvent such as CH2Cl2 during work up to remove the support, reagents or side-products. Therefore, it is desirable to develop simple, efficient, and green methods for the synthesis of 4(3H)-quinazolinones. In this regard, in recent years, molecular iodine has received considerable attention as an inexpensive and easily available catalyst for various organic transformations such as esterification,17 oxidation,18 acetylation,19 Hantzsch,20 Biginelli reaction,21 aziridination,22 allylation,23 Michael addition,24 Johnson–Claisen rearrangement,25 and Diels–Alder reactions.26 We report the synthesis of 3-aryl 4(3H)-quinazolinones by the condensation of anthranilic acid 1, ortho esters 2 and aromatic amines 3 in the presence of a catalytic amount of I2 at room temperature without solvent (Scheme 1). A model reaction of anthranilic acid with triethyl orthoformate and aniline carried out at room temperature in the absence of catalyst gave only a 5% yield after 1 h. However, a