Three-Component [2+2+1] Gold(I)-Catalyzed Oxidative Generation of Fully Substituted 1,3-Oxazoles Involving Internal Alkynes

Three-component [2+2+1] gold(I)-catalyzed reaction of internal alkynes (alkynyl esters or -ketones), nitriles, and 2-chloropyridine N-oxide led to a wide range of fully substituted 1,3-oxazoles (32 examples; up to 92% isolated yields). Nitrile (RCN)-C-3 species, employed in the reaction as both reactants and solvents, comprise conventional nitriles (R-3 = Alk, Ar) and also push-pull systems such as cyanamides (R-3 = NH2 and NAlk(2)) and the thiocyanate (R-3 = SPr). The advantages of the developed method include mild reaction conditions, high functional-group tolerance, broad range of substituents R-1/R-3 along with a possibility of easy modification of COR2 or the amino group when R-1 = NH2.