N-Benzoyl-N'-(2-carboxy- and 2-methoxycarbonylphenyl)thioureas have been obtained by the reaction of N-benzoyl isothiocyanate with anthranilic acid and methyl anthranilate, respectively. Kinetics of cyclization of these compounds into 2-mercapto-3,4-dihydro-4-quinazolone have been studied in water and in methanol. In the base-catalyzed cyclization of N-benzoyl-N'-(2-carboxyphenyl)thiourea the proper cyclization is preceded by solvolysis of the benzoyl group. In the case of N-benzoyl-N'-(2-methoxycarbonylphenyl)thiourea the reaction rate is limited by the base-catalyzed cyclization of the starting benzoyl derivative; the benzoyl group is split off in a subsequent rapid step.

Die Kinetik der basenkatalysierten Cyclisierung des Thioharnstoffs (IIb) [bei höherer Basenkonzentration entsteht neben dem Anion (III) noch das Dianion (IV)] in Methanol und Wasser sowie die Kinetik der Methanolyse und der Hydrolyse von (IIa) und der Cyclisierung des Zwischenprodukts (V) der (IIb)‐Cyclisierung werden untersucht.