Synthesis and Antibacterial Screening of Some 1-Aroyl-3-aryl Thiourea Derivatives

A series of 1-aroyl-3-aryl thioureas derivatives were synthesized and evaluated for antibacterial activity. The results indicated that the compounds possessed higher activity against gram-negative bacteria than gram-positive bacteria. Amongst all these compounds, C18 (89.4%) exhibited the greatest antibacterial activity against gram-negative bacteria while C5 (85.6%) displayed maximum antibacterial activity against gram-positive bacteria. Preliminary study of the structure-activity relationship revealed that an electronic factor on aryl rings had a great effect on the antibacterial activity of these compounds. 1. Introduction The increased use of antibacterial and antifungal agents has resulted in the development of drug resistant microbial pathogens which results in failure in clinical application of these agents. This highlights the incessant need for the development of new classes of antimicrobial agents and alteration of known drugs in such way that would allow them to retain their physiological action but reduce their resistance to the pathogen. Thiourea derivatives are versatile building blocks for the synthesis of a variety of heterocyclic compounds and display a wide spectrum of biological activities such as antimicrobial [1–4], antimalarial [5], antitubercular [6], anticancer [7], anti-HIV [8], carbonic anhydrases inhibitor [9], appetite suppressants [10], β3-adrenergic receptor agonists [11], and CNS activity [12]. Therefore, their beneficial properties have prompted several groups to study these compounds. We have been interested in antimicrobial agents for a few years and have performed QSAR analysis and synthesis of antimicrobial agents [13–15]. Here in the present work we report the synthesis and screening of some 1-aroyl-3-aryl thiourea derivatives for their antimicrobial potency. 2. Experimental Synthesis of some 1-aroyl-3-aryl thioureas (C1–C18) (Figure 1 and Table 1) was carried out by treating substituted benzoyl chloride with an equimolar quantity of potassium thiocyanate in acetone followed by reaction with an equimolar amount of substituted anilines to furnish the 1-aroyl-3-aryl thiourea derivatives. Table 1: Synthesized 1-aroyl-3-aryl thiourea derivatives. Figure 1: Synthesis of 1-aroyl-3-aryl thiourea. 2.1. General Procedure for the Synthesis of 1-Aroyl-3-aryl Thioureas A solution of substituted benzoyl chloride (10？mmol) in acetone (50？mL) was added dropwise to a suspension of potassium thiocyanate (10？mmol) in acetone (30？mL) and the reaction mixture was refluxed for 30？min. After cooling to room temperature, a solution of