title: Regiocontrol in catalytic reductive couplings through alterations of silane rate dependence.
abstract: Combinations of ligand, reducing agent, and reaction conditions have been identified that allow alteration in the rate- and regioselectivity-determining step of nickel-catalyzed aldehyde-alkyne reductive couplings. Whereas previously developed protocols involve metallacycle-forming oxidative cyclization as the rate-determining step, this study illustrates that the combination of large ligands, large silanes, and elevated reaction temperature alters the rate- and regiochemistry-determining step for one of the two possible product regioisomers. These modifications render metallacycle formation reversible for the minor isomer pathway, and σ-bond metathesis of the metallacycle Ni-O bond with the silane reductant becomes rate limiting. The ability to tune regiocontrol via this alteration in reversibility of a key step allows highly regioselective outcomes that were not possible using previously developed methods.
authors.affiliation: Department of Chemistry, University of Michigan , 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States.
authors.forename: Evan P
authors.initials: EP
authors.lastname: Jackson
authors.forename: John
authors.initials: J
authors.lastname: Montgomery
mesh_terms: D002384:Catalysis; D007700:Kinetics; D019163:Reducing Agents / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D019163:Reducing Agents; D012821:Silanes