The Petasis reaction (alternatively called the Petasis borono–Mannich (PBM) reaction) is the chemical reaction of an amine, aldehyde, and vinyl- or aryl-boronic acid to form substituted amines.Reported in 1993 by Nicos Petasis as a practical method towards the synthesis of a geometrically pure antifungal agent, naftifine, the Petasis reaction can be described as a variation of the Mannich reaction. Rather than generating an enolate to form the substituted amine product, in the Petasis reaction, the vinyl group of the organoboronic acid serves as the nucleophile. In comparison to other methods of generating allyl amines, the Petasis reaction tolerates a multifunctional scaffold, with a variety of amines and organoboronic acids as potential starting materials. Additionally, the reaction does not require anhydrous or inert conditions. As a mild, selective synthesis, the Petasis reaction is useful in generating α-amino acids, and is utilized in combinatorial chemistry and drug discovery.