Umpolung Reactivity of Ynamides: An Unconventional [1,3]‐Sulfonyl and [1,5]‐Sulfinyl Migration Cascade

A regioselective sulfonyl/sulfinyl migration cycloisomerization cascade of alkyne‐tethered ynamides is developed in the presence of XPhosgold catalyst. This reaction is the first example of a general [1,3]‐sulfonyl migration from the nitrogen center to the β‐carbon atom of ynamides, followed by umpolung 5‐endo‐dig cyclization of the ynamide α‐carbon atom to the gold‐activated alkyne, and final deaurative [1,5]‐sulfinylation. This process allows the synthesis of peripherally decorated unconventional 4‐sulfinylated pyrroles with broad scope from N‐propargyl‐tethered ynamides. In contrast, N‐homopropargyl‐tethered ynamides undergo intramolecular tetradehydro Diels–Alder reaction to provide 2,3‐dihydro‐benzo[f]indole derivatives. Control experiments and density‐functional theory studies were used to study the reaction pathways. Double migration: A regioselective umpolung [1,3]‐sulfonyl/[1,5]‐sulfinyl migration cycloisomerization cascade of alkyne‐tethered ynamides allows the construction of unconventional 4‐sulfinylated pyrroles through deaurative [1,5]‐sulfinylation. Density functional theory was used to study the reaction pathway.