en Pharmacy Review <span style="font-size:13pt"><span style="line-height:150%"><span new="" roman="" style="font-family:" times=""><span style="font-size:12.0pt"><span style="line-height:150%">This mini-review provides a chronological and mechanistic overview of synthetic developments leading from salicylic acid to mesalazine (5-aminosalicylic acid). Historical nitration routes (1843&ndash;1954) relied on mineral acids under uncontrolled conditions, while modern approaches (2005&ndash;2025) have achieved regioselective 5-nitration with yields exceeding 85% using catalytic, microwave-assisted, or solvent-free systems. Subsequent reduction of 5-nitrosalicylic acid to its amine derivative has evolved from tin or sulfide reagents to environmentally benign catalytic hydrogenations, electrochemical, and mechanochemical protocols. Recent industrial patents and academic studies demonstrate scalable aqueous hydrogenations with precise pH control and remarkable product selectivity.&nbsp;&nbsp;</span></span></span></span></span><br> &nbsp; Mesalazine, Salicylic acid, 5-Nitration, Nitro reduction, Green chemistry 36 45 http://tbsrj.mazums.ac.ir/browse.php?a_code=A-10-3627-2&slc_lang=en&sid=1 Seyyed Amir Siadati Chemistry_2021@yahoo.com 100319475328460032040 100319475328460032040 Yes melika Ebrahimzadeh zadeh20@gmail.com 100319475328460032041 100319475328460032041 No E Babanezhad esmaeil.babanezhad@gmail.com 100319475328460032042 100319475328460032042 No