NHC–Gold(I) Complexes as Effective Catalysts for the Carboxylative Cyclization of Propargylamines with Carbon Dioxide

NHC–gold­(I)
complexes promote carboxylative cyclization
of a range of propargylic amines to afford (Z)-5-alkylidene-1,3-oxazolidin-2-ones
in methanol under neutral and mild conditions. The highly active and
robust catalyst permits CO2 utilization under a mixed gas
atmosphere containing CO or H2. As a key intermediate,
a new alkenylgold­(I) complex was successfully identified from a stoichiometric
reaction of Au­(OH)­(IPr) and 1-methylamino-2-butyne in THF. The methanol
solvent influences the formation of catalytically active cationic
gold species and facilitates protodeauration from the alkenylgold
complex to release the cyclic urethane product due to in situ generation
of methylcarbonic acid in the presence of CO2.