Quinazolin-4-ones, 3-aryl-2-methyl

Methoxide converted a series of X-phenyl iV-(4-thiocarboxamidophenyl)carbamates (32 X = 4-MeO, 3-MeO, 4-C1, 3-C1, H) into methyl )V-(4-thiocarboxamidophenyl) carbamate (33) and the corresponding phenate via an E cB mechanism (Scheme 11). However, when a series of the corresponding aryl )V-(2-thiocarboxamidophenyl)car-bamates (34 R1 = H, R2 = 4-MeO, 3-MeO, 4-Me, 3-C1, 4-C1, 3-N02, H) were treated similarly, a rapid intramolecular cyclization occurred to give 4-thioxo-lH,3H-quinazolin-2-one (35 R1 = H) and the corresponding phenate (Scheme 12). All the... 

The quinazolinone structure is found in many biologically active compounds methaqualone, mecloqualone, piriqualone, afloqualone, and so on. Methaqualone (MQ, 470), 2-methyl-3-(2-methylphenyl)quinazolin (3H)-one, an hypnotic and anticonvulsive drug, is one of the leading examples of atropisomeric six-membered N-aryl heterocycles. Methaqualone gives stable atropisomers at room temperature due to the three substituents in ortho positions of the N-aryl rotating bond. 

Some new facile syntheses for 2-methyl-3-(o-tolyl)quinazolin-4-one (methaqualone) " and 3-aryl-2-mercapto-quinazolin-4-ones have been announced. The former synthesis can be carried out in high yield in one pot by allowing isatoic anhydride to react sequentially with aniline in toluene and pentane-2,5-dione in ethanolic hydrogen chloride. The latter preparation consists of condensing aryl isothiocyanates with anthranilic acid in hot acetic acid-sodium acetate mixture. 

Aryl-5H-l,3,4-thiadiazolo[2,3-b]quinazolin-5-ones (216) are accessible in moderate yield by the condensation of 2-chloro-l,3,4-thiadiazoles and methyl anthranilate in boiling acetic acid. ... 

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