Cobalt-Mediated Reactions of Oxazoles and Thiazoles with Alkynes

Abstract An experimental foray into the potential of oxazoles and thiazoles to enter into CpCo-mediated [2+2+2] cycloadditions is described. α,ω-Diynes failed to engage the heterocycles productively, as illustrated by the behavior of the unique cobaltacyclopentadiene(oxazole) complex 10 , the isolation and X-ray structural determination of which is recorded. Alkyne-tethered systems gave moderate yields to products resulting from [2+2+2] cycloaddition and C–H activation. The azaenol ether bridge in the cycloaddition products appears sensitive to oxidation, elimination, and rearrangement, depending on the system and reaction conditions.