Sulfur(iv)-mediated umpolung α-heterofunctionalization of 2-oxazolines

The alpha-umpolung of carbonyl compounds significantly expands the boundaries of traditional carbonyl chemistry. Despite various umpolung methods available today, reversing the inherent reactivity of carbonyls still remains a substantial challenge. In this article, we report the first use of sulfonium salts, in lieu of well-established hypervalent iodines, for the carbonyl umpolung event. The protocol enables the incorporation of a wide variety of heteroatom nucleophiles into the alpha-carbon of 2-oxazolines. The success of this investigation hinges on the following factors: (1) the use of sulfoxides, which are abundant, structurally diverse and tunable, and easily accessible, ensures the identification of a superior oxidant namely phenoxathiin sulfoxide for the umpolung reaction; (2) the assembly/deprotonation protocol previously developed for rearrangement reactions in our laboratory was successfully applied here for the construction of alpha-umpoled 2-oxazolines.

Automated summary

In this article, the use of sulfonium salts for carbonyl umpolung event is reported, allowing the incorporation of heteroatom nucleophiles into the alpha-carbon of carbonyl compounds.