https://doi.org/10.1177/1747519819883840 Journal of Chemical Research 1–12 © The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1747519819883840 journals.sagepub.com/home/chl Introduction Phthalazine, also known as benzo-orthodiazine, 2,3-diazon- aphthalene, and benzo[d]pyridazine, is a compound in which pyridazine is fused with a benzene ring. Although, N-containing heterocyclic compounds are widely distributed in nature, the presence of two adjacent nitrogen atoms in the phthalazine ring makes it rare and not very familiar in isolated extracts from living organisms, owing to the fact that it can be constructed from hydrazine which is an uncommon amine source in nature. Phthalazines and phthalazine hybrids as antimicrobial agents: Synthesis and biological evaluation Asmaa Kamal Mourad , Abdelmoneim Abdelsalam Makhlouf, Ahmed Yousef Soliman and Samar Ahmed Mohamed Abstract Phthalazine and phthalazinone derivatives are important owing to their significant biological activities and pharmacological properties. Herein, a benzoic acid derivative (2), a benzoxazin-1-one derivative (3), and an oxophthalazin-2(1H)-yl) acetohydrazide (13) are utilized as precursors to construct a novel series of phthalazinones bearing various valuable functional groups in excellent yields via several simple and promising approaches. Finally, the antimicrobial activity of the newly synthesized phthalazines is screened against different microbial strains; namely, Gram-negative and Gram-positive bacteria utilizing Amoxicillin as a standard drug. Keywords benzoxazinone, Friedel Craft’s reaction, 1,3,4-oxadiazole, phthalazine, pyrazole Date received: 28 July 2019; accepted: 1 October 2019 Chemistry Department, Faculty of Science, Fayoum University, Fayoum, Egypt Corresponding author: Asmaa Kamal Mourad, Chemistry Department, Faculty of Science, Fayoum University, Fayoum 63514, Egypt. Email: akk00@fayoum.edu.eg 883840CHL 0 0 10.1177/1747519819883840Journal of Chemical ResearchMourad et al. research-article 2019 Research Paper