Cu-Catalyzed Conversion of Propargyl Acetates to E-α,β-Unsaturated Amides via Ketenimine Formation with Sulfonyl Azides

The reaction between readily accessible propargyl acetates and sulfonyl azides in the presence of CuI catalyst yields trans-alpha,beta-unsaturated N-tosylamides via N-sulfonyl ketenimine formation followed by a probable 1,3-OAc migration ([3,3]-sigmatropic rearrangement). The reaction is very general, allowing all kinds of substitution, including alkyl, aryl (electron-donating, -withdrawing, and -neutral), heteroaryl, and vinyl groups, on the C-terminal of acrylamide. Also, the method affords the products at ambient temperature with excellent diastereoselectivity in moderate to good yields.