2-Fluoro-3-methoxybenzaldehyde (CAS number 103438-88-6) is a benzaldehyde building block, bearing a fluoride and a methoxy at 2- and 3-positions. 2-Fluoro-3-methoxybenzaldehyde finds widespread use as a precursor for active pharmaceutical ingredients (APIs), particularly in the synthesis of benzosuberone derivatives. To construct benzosuberone cores, 2-fluoro-3-methoxybenzaldehyde reacts with (3-carboxypropyl)triphenylphosphonium bromide through a Wittig reaction. The formation of cycloheptanone ring is achieved through a Friedel-Craft acylation using Eaton's reagent (phosphorus pentoxide and methanesulfonic acid).
2-Fluoro-3-methoxybenzaldehyde is also employed in the synthesis of bicyclic heterocycles, including hydroisoquinolines, acrydinone and quinazolines.