Pd‐Catalyzed, Ligand‐Enabled Stereoselective 1,2‐Iodine(III) Shift/1,1‐Carboxyalkynylation of Alkynylbenziodoxoles

A PdII‐catalyzed 2:1 coupling reaction of alkynylbenziodoxole with carboxylic acid to afford (alk‐1‐en‐3‐ynyl)benziodoxole, which is efficiently promoted by an octahydrophenazine ligand, is reported. The reaction involves a Pd‐assisted 1,2‐iodine(III) shift of the alkynylbenziodoxole followed by stereoselective introduction of carboxy and alkynyl groups (the latter originating from another molecule of the alkynylbenziodoxole) into the 1‐position of the transient Pd‐vinylidene species. The product of this 1,1‐carboxyalkynylation reaction serves as a new functionalized enyne‐type building block for further synthetic transformations. Shifty iodine: A PdII‐octahydrophenazine catalyst promotes 2:1 coupling of alkynylbenziodoxole with carboxylic acid. The reaction involves a PdII‐assisted 1,2‐iodine(III) shift of the alkynylbenziodoxole followed by stereoselective introduction of carboxy and alkynyl groups into the 1‐position of the transient Pd‐vinylidene species. The product of this 1,1‐carboxyalkynylation reaction serves as a new functionalized enyne‐type building block for further synthetic transformations.