Gold‐Catalyzed Oxygen Transfer to Alkynylsulfones: A Diazo‐Free Route to 4‐Sulfonyl‐1,3‐Oxazoles
Elena I. Chikunova, Dmitry Dar’in, Vadim Yu. Kukushkin, Alexey Yu. Dubovtsev
Abstract
Abstract The gold‐catalyzed annulation of alkynylsulfones, involving pyridine N ‐oxides (as O ‐atom transfer reagents) and nitriles (as C=N synthons), comprises a diazo‐free route to valuable 4‐sulfonyl‐1,3‐oxazoles. This reaction operates under relatively mild conditions (IPrAuNTf 2 5 mol %, rt or 60 °C), and a number of functionalities was compatible (35 examples; 14–95%). In most cases, the SO 2 fragment, which is typically expulsed in the previously reported Au‐catalyzed O ‐transfers to alkynylsulfones, retains in the heterocyclic products. The postulated reaction mechanism suggests a key role of reactive gold α‐oxo carbene intermediates formed via the O ‐atom transfer. magnified image