Transition Metal-Free Formal C─H/C─H Coupling of Arylacetamides and Sulfoxides: An Interrupted Pummerer/[2,3]-sigmatropic Rearrangement Sequence.

Arylacetamides are important structural motifs found in many bioactive compound classes. Given their significance, the selective decoration of arylacetamides by transition metal-catalyzed C─H activation has attracted considerable attention. Here, we report a two-step transition metal-free formal C─H/C─H coupling of arylacetamides with sulfoxides that proceeds via the formation and rearrangement of little-known α-amido sulfonium salts; the amide motif "catches" the sulfoxide partner prior to its delivery to the ortho-position of the aromatic ring by rearrangement of a sulfur ylide intermediate. The approach delivers alkylated arylacetamides bearing sulfide functional handles that can be exploited in downstream manipulations. This protocol has allowed the synthesis of a dopamine D1 receptor allosteric modulator without recourse to the use of transition metals.