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

A regioselective sulfonyl/sufinyl migration cycloisomerization cascade of alkyne‐tethered ynamides is developed in the presence of XPhos‐gold catalyst. This is the first example of a general [1,3]‐sulfonyl migration from the nitrogen to the β‐carbon of ynamides, followed by umpolung 5‐endo‐dig cyclization of the ynamide α‐carbon to the gold activated alkyne, and finally deaurative [1,5]‐sulfinylation. This process allows the synthesis of peripheral decorated unconventional 4‐sulfinylated pyrroles with a broad scope from N‐propargyl‐tethered ynamides. On the other hand, 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 (DFT) studies help rationalizing these reaction pathways.

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