The work presented in this thesis revolves around the mechanistic and the development of Ni-catalyzed processes. In 2018, our group reported a catalytic method for the synthesis of diversely 2-substituted 1,3-dienes. This work describes the synthesis of conjugated dienes via Ni-catalyzed cross coupling between a vinyl Grignard and enol phosphates. This methodology relies on the use of two complementary biphosphine-nickel complexes – [(dppe)NiCl₂] and [(dmpe)NiCl₂].

Nickel has been well documented for standing apart from other transition metals in d¹⁰ column due to its smaller size, lower reduction potential and lower electronegativity. Its proclivity to access a larger range of oxidation state than palladium, leads to diverse mechanistic scenarios. However, there are few examples of mechanistic studies delving into Ni-catalyzed reactions using C(sp²)–O electrophiles such as aryl ethers, aryl sulfamates, aryl esters and aryl carbonates. Examples dealing with mechanistic investigations of reactions with the vinyl counterparts of the aforementioned functions are even scarcer. The work presented in this Thesis aims at giving a deeper and finer understanding of the studied coupling. Based on supporting stoichiometric organometallic syntheses, structural analyses, reaction monitoring, radical-clock experiments and kinetic investigations, a comparative mechanistic study between the two precatalysts has been conducted. We demonstrate that the two bisphosphine-nickel complexes operate via distinct Ni(0)/Ni(II) catalytic manifolds.

Nickel-catalyzed functionalization of alkynes with aryl boronic acids represents a swift gateway to the construction of value-added stereochemically defined highly substituted olefins. The work described in this Thesis deals with the development of a stereo- and regioselective Ni-catalyzed hydroarylation of enynones. Of this project branched out two new reactions. A Ni-catalyzed carbometalative cyclization of enynones with electrophile-tethered aryl boronic acids granting access to indanones scaffolds. A Ni-catalyzed hydroalkoxylation of the C≡C bond of enynones providing a way to highly substituted enol ethers.