Research Article Remarkable Conversion of 2-Thioxo-2,3-dihydroquinazolin-4(1H)-ones into the Corresponding Quinazoline-2,4(1H,3H)-diones: Spectroscopic Analysis and X-Ray Crystallography Adel S. El-Azab , Nasr Y. Khalil , and Alaa A.-M. Abdel-Aziz Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia Correspondence should be addressed to Adel S. El-Azab; adelazab@ksu.edu.sa Received 21 December 2020; Revised 5 March 2021; Accepted 13 March 2021; Published 2 April 2021 Academic Editor: Xi Liu Copyright © 2021 Adel S. El-Azab et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A simple and efficient new synthetic method to obtain 3-substituted quinazolin-2,4-diones 9 – 16 by the reaction of 3-substituted 2- thioxo-quinazolin-4-ones 1 – 8 with sodamide under mild conditions was presented. e structure of the newly synthesized compounds was determined by infrared spectroscopy, UV-visible spectroscopy, nuclear magnetic resonance, and single-crystal X-ray crystallo- graphic analysis. e crystal structure of 6-methyl-3-phenylquinazoline-2,4(1H,3H)-dione ( 11) [C 15 H 12 N 2 O 2 : MF � 252.27, triclinic, P-1, a � 7.8495 (13) ˚ A, b � 12.456 (2) ˚ A, c � 13.350 (2) ˚ A, α � 103.322 (3) ° , β � 90.002 (3) ° , c � 102.671 (4) ° ,V � 1237.5 (3) ˚ A 3 , Z � 4, R � 0.0592, wR � 0.1699, S � 1.039] was determined. In the crystal cell, two identical conformers of compound 11 were found connected by intramolecular hydrogen bonds, responsible for the favourable occurrence of these two independent molecules. 1. Introduction e oxidation of thiones into carbonyl compounds has attracted the interest of organic chemists since the early 19 th century [1]. Diverse method for this conversion was de- veloped, such as oxidative procedure by organic and inor- ganic reagents. e oxidation of thiocarbonyl compounds into carbonyl compounds can be performed using different oxidative reagents. Potassium permanganate [2–10] and lead tetra acetate were used to oxidize cyclic thiocarbonate into the corresponding carbonate [8, 11]. e oxidation of thi- oamide into the corresponding amides was achieved using manganese dioxide, ceric ammonium nitrate, and copper nitrate [12–14]. Hydrogen peroxide and peroxy acids were used to oxidate different thioketones into the corresponding ketones [15, 16]. Conversely, molecular oxygen and ozon- ation were used to oxidate thione into the corresponding ketones [17–22]. e oxidation of thione compounds into the related carbonyl compounds was achieved using sele- nium oxide and tin oxides [23–27]. Moreover, quinazolinones, such as quinazolin-2,4-dio- nes, and their corresponding 2-thioxo-quinazolin-4-ones undergo several biological activities, such as carbonic anhydrase [28–31], COX-1/2 [32, 33], tyrosine kinase in- hibitions [34], and antitumor activity [35–41]. Due to the biological importance of quinazolin-2,4-diones and 2-thi- oxo-quinazolin-4-ones, their molecular structures are studied by spectroscopic and theoretical methods [42–46]. Moreover, urea molecule, which constitutes quinazolin-2,4- dione, was extensively studied experimentally and theoret- ically [47–55]. e crystal form of urea showed a planar conformation, indicating a network of hydrogen bonds [56]. In this study, a new simple methodology was used to oxidate the different quinazolin-2-thiones into the corre- sponding 2,4-quinazolindione; this was achieved by heating the different quinazolin-2-thiones with sodamide in Hindawi Journal of Chemistry Volume 2021, Article ID 6612177, 8 pages https://doi.org/10.1155/2021/6612177