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.