Dinickel Catalyzed Vinylidene-Alkene Cyclization Reactions

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Reductive cyclization reactions are crucial for synthesizing cyclic organic molecules.
• Developing efficient catalysts for these transformations is an ongoing challenge in synthetic chemistry.

Purpose of the Study:

• To investigate the efficacy of a dinickel catalyst in promoting reductive cyclization reactions.
• To elucidate the reaction mechanism and identify key intermediates.
• To explore both chemical and electrochemical methods for driving the cyclization.

Main Methods:

• Utilized a dinickel catalyst for reductive cyclization of 1,1-dichloroalkenes with pendant olefins.
• Employed zinc reductant and electrocatalysis (carbon working electrode) for the reactions.
• Conducted mechanistic studies including structural characterization of a dinickel metallacycle.
• Performed spin-polarized, unrestricted Density Functional Theory (DFT) calculations.

Main Results:

• The dinickel catalyst successfully promoted reductive cyclization reactions.
• Mechanistic studies supported the formation of a Ni2(vinylidene) species and a dinickel metallacycle intermediate.
• β-Hydride elimination and C-H reductive elimination were identified as key steps in product formation.
• The dinickel metallacycle was structurally characterized and its stoichiometric conversion demonstrated.
• DFT calculations confirmed the cooperative role of both nickel centers in the catalytic cycle.

Conclusions:

• Dinickel catalysts are effective in promoting reductive cyclization of dichloroalkenes.
• The reaction proceeds through a well-defined dinickel metallacycle intermediate.
• Both chemical and electrochemical methods can be employed for this transformation.
• Computational modeling provides valuable insights into the cooperative mechanism of dinickel catalysts.