Stereodefined synthesis of a new type of 1,3-dienes by ligand-controlled carbon-carbon and carbon-heteroatom bond formation in nickel-catalyzed reaction of diaryldichalcogenides with Alkynes

We have found that ligand control over the carbon-carbon and carbon-heteroatom bond formation on the nickel center provides an easy and convenient route to symmetrical (minor) and unsymmetrical (major) isomers of sulfur- and selenium-substituted 1,3-dienes. The unsymmetrical product is a new type of 1,4-substituted conjugated diene, which was readily synthesized from alkynes and diaryidichalcogenides. The unique feature of this developed one-pot transformation is total stereodefined synthesis of the diene skeleton, controlling not only the configuration of the double bond but also the s-gauche conformation of the central C-C bond. The mechanistic study revealed the key feature of alkyne insertion into the Ni-E and Ni-C bonds (E = S, Se), which governs the direction of the chemical transformation.