Monatshefte f€ ur Chemie 135, 283–291 (2004) DOI 10.1007/s00706-003-0058-5 Synthesis, Properties, and Reactions of 5-Substituted Derivatives of 2,3-Diphenylquinoxaline [1] Jozef Salon ˇ 1 , Viktor Milata 1; , Miloslav Chudı ´k 1 , Nadez ˇda Pro ´nayova ´ 2 , Ja ´n Les ˇko 2;y , Milan Seman 3 , and Anna Belicova ´ 3 1 Department of Organic Chemistry, Faculty of Chemical Technology, Slovak Technical University, SK-812 37-Bratislava, Slovakia 2 Central laboratory of Chemical Technique, Faculty of Chemical Technology, Slovak Technical University, SK-812 37-Bratislava, Slovakia 3 Institute of Cells Biology, Faculty of Natural Sciences of the Comenius University, SK-811 07 Bratislava, Slovakia Received March 27, 2003; accepted (revised) April 15, 2003 Published online December 30, 2003 # Springer-Verlag 2003 Summary. Catalytic hydrogenation of 5-nitro-2,3-diphenylquinoxaline led to the corresponding amine which, in turn, afforded products of nucleophilic substitution on reaction with alkoxymethylene derivatives. Thermal cyclization of selected alkoxymethylene derivatives yielded substituted pyrido- quinoxalines. The conditions for successful hydrolysis of ester, decarboxylation of the acid, following chlorination of pyridone and reductive removal of the chlorine atom from it to produce parental heterocycle 2,3-diphenyl-pyrido[2,3-f ]quinoxaline were found. All of the tested products of the nucleo- philic substitution showed no antibacterial activity. Keywords. Nucleophilic substitutions; Enols; Cyclizations; Pyridoquinoxalines; Antibacterial activity. Introduction Numerous quinoxaline derivatives have attracted attention by their biological importance and have been synthesized by many research groups [2]. For example, quinoxaline-2-one has been shown to possess anti-inflammatory, tranquilizing, and antidepressant properties. Imidazoquinoxalines have even been found to be strong carcinogens in food [3]. Due to this and in continuation of our strategy aiming at  Corresponding author. E-mail: vmilata@cvt.stuba.sk y Dedicated to Prof. Dr. M. Uher on the occasion of his 65 th birthday