31502-35-9Relevant academic research and scientific papers
Ni-Catalyzed Regioselective β,δ-Diarylation of Unactivated Olefins in Ketimines via Ligand-Enabled Contraction of Transient Nickellacycles: Rapid Access to Remotely Diarylated Ketones
Basnet, Prakash,Dhungana, Roshan K.,Thapa, Surendra,Shrestha, Bijay,Kc, Shekhar,Sears, Jeremiah M.,Giri, Ramesh
supporting information, p. 7782 - 7786 (2018/06/22)
We disclose a [(PhO)3P]/NiBr2-catalyzed regioselective β, δ-diarylation of unactivated olefins in ketimines with aryl halides and arylzinc reagents. This diarylation proceeds at remote locations to the carbonyl group to afford, after simple H+ workup, diversely substituted β, δ-diarylketones that are otherwise difficult to access readily with existing methods. Deuterium-labeling and crossover experiments indicate that diarylation proceeds by ligand-enabled contraction of transient nickellacycles.
On the mechanism of the nickel-catalysed regioselective cyclodimerization of isoprene
van Leeuwen,Roobeek
, p. 1973 - 1983 (2007/10/02)
A study of various Ni-ligand catalysed oligomerizations of isoprene has shown that with π-acidic P ligands the selectivity to cyclodimers amount to 97%. A new type of ligand is introduced, viz. fluoroalkyl phosphites having π-acceptor properties comparable to those of, e.g. PCl3. With tris(hexafluoroisopropyl) phosphite the main product is 1,4-dimethy1-4-vinylcyclohexene. A detailed explanation based on a two-step mechanism is given. As to the first step, for a series of ligands having similar steric properties the changes in product distribution as a function of the electronic ligand parameter are explained in terms of a gradual change in HOMO-LUMO interactions between Ni and the olefins, with strong π-acidic ligands promoting the head-to-head coupling of the isoprene molecules. The second step, involving reductive elimination of a cyclodimer from the metal, shows an increasing selectivity towards substituted cyclohexenes for the head-to-head and tail-to-tail intermediates with increasing π-acidity of the ligand. The qualitative orbital treatment presented as an explanation is also applicable to reactions found for other metallacyclopentanes.
