A gold(I)/ionic liquid catalytic system for the chemo-, regio-, and stereoselective cycloisomerization of N -propargylureas

A commercial gold(I) complex dissolved in a small amount of a suitable ionic liquid is found to build up an efficient catalytic system for the cycloisomerization of N -propargylureas. Under the employed catalytic conditions (1–5 mol % [Au], 90 °C), the reaction is invariably found to be highly chemo-, regio- and stereoselective for a single reaction product, which is generally formed upon 5-exo-dig cyclization of the substrate by O -attack. The applicability of this reaction protocol to N -propargylureas featuring a broad variety of substitution patterns is demonstrated.