Oxazole Synthesis by Sequential Asmic-Ester Condensations and Sulfanyl–Lithium Exchange–Trapping

Oxazoles are rapidly assembled through a sequential deprotonation–condensation of Asmic, anisylsulfanyl­methyl­isocyanide, with esters followed by sulfanyl–lithium exchange–trapping. Deprotonating Asmic affords a metalated isocyanide that efficiently traps esters to afford oxazoles bearing a versatile C-4 anisylsulfanyl substituent. Interchange of the anisylsulfanyl substituent is readily achieved through a first-in-class sulfur–lithium exchange–electrophilic trapping sequence whose versatility is illustrated in the three-step synthesis of the bioactive natural product streptochlorin.