Formation of Oxazoles from Elusive Gold(I) α-Oxocarbenes: A Mechanistic Study.
The gold(I) catalyzed reaction between phenylacetylene, pyridine N-oxide and acetonitrile leading, via a putative gold-α-oxocarbene intermediate, towards an oxazole product has been investigated. A novel mass spectrometric method called "delayed reactant labeling" is used to track consecutive and parallel reactions. It clearly shows that the intramolecular formation of a pyridine adduct of gold-α-oxocarbene is in competition with the formation of the oxazole product. The reaction mechanism most probably corresponds to competition between acetonitrile and pyridine in an almost barrierless reaction with putative gold-α-oxocarbene within the solvent cage. The detected ionic species have been characterized by helium tagging infrared photodissociation spectroscopy.
Department of Organic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, 128 43, Prague, Czech Republic.
Jiří
J
Schulz
Department of Organic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, 128 43, Prague, Czech Republic.
Juraj
J
Jašík
Department of Organic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, 128 43, Prague, Czech Republic.
Andrew
A
Gray
Department of Organic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, 128 43, Prague, Czech Republic. roithova@natur.cuni.cz.
Jana
0000-0001-5144-0688
J
Roithová
carbenes; gold catalysis; mass spectrometry; reaction intermediates; reaction mechanism