Mechanistic Understanding of a Silver Pyridylpyrrolide as a Catalyst for 3 + 2 Cyclization of a Nitrile with Diazo Ester

The trinuclear argentate complex Ag3(μ2-3,5-(CF3)2PyrPy)3 (PyrPy = 2,2′-pyridylpyrrolide) catalyzes the 3 + 2 cycloaddition of several NCR (R = Me, Ph, tBu) and N2CHCO2Et to disubstituted oxazoles, even in the presence of light and air. Structural and theoretical studies imply a three-coordinate silver carbene complex, (3,5-(CF3)2PyrPy)Ag(CHCO2Et), to be responsible in a stepwise nitrile addition and cyclization step to form the heterocycle.