Ir‐Catalyzed Sulfur‐Directed Vinylic C─H Activation for the Stereoselective Synthesis of 1,3‐Dienes Using Alkynoates

Abstract Vinylic sp 2 C─H alkenylation with alkynoates was investigated in the presence of a cationic iridium catalyst using aryl 2‐substituted allyl sulfides as substrates. In the reaction of dimethyl acetylenedicarboxylate, the double bonds were isomerized from the expected C─H alkenylated products, and sulfur‐containing 1,3‐dienes were obtained stereoselectively. A mechanism study suggested that the stereospecific isomerization involves thermal 1,5‐sigmatropic rearrangement. On the other hand, in the case of phenylpropiolates, a regio‐ and stereoselective C─H alkenylation proceeded without isomerization when the reaction was stopped at low conversion.