Mechanistic investigation of 1,3-dipolar cycloaddition between bifunctional 2-pyridylselenyl reagents and nitriles including reactions with cyanamides

Novel selenodiazolium salts derived from the reaction between 2-pyridylselenyl reagents and cyanamides are described and fully characterized. Eight adducts were studied by means of single crystal structural analysis, which revealed the presence of four-center N⋯Se interactions for some of them with an estimated interaction energy of −3.9 kcal mol−1, as revealed by theoretical calculations. Importantly, the reaction mechanism between nitriles of the general formulae RC ≡ N (R = Me, Ph, Br, CCl3, Me2N, Ph(H)N) and 2-pyridylchalcogenyl halides 2-PyChX (Ch = Se, Te; X = Cl, Br) was investigated by theoretical methods, which suggested the asynchronous cycloaddition nature of the process. © 2023 The Royal Society of Chemistry.