Fast Palladium Catalyzed Arylation of Alkenes Using Bulky Monodentate Phosphorus Ligands

Abstract

Complex 1bshows an unprecedented high activity in the Heck reaction. Kinetic studies show that in this system not the oxidative addition but the alkene coordination/migratory insertion is the rate determining step.

Strong evidence of solution-phase catalysis associated with palladium leaching from immobilized thiols during Heck and Suzuki coupling of aryl iodides, bromides, and chlorides

“…6, curve C), presumably when nanoparticle formation could have already occurred, is suggested as evidence that if nanoparticles are formed, their surface is inactive, as postulated above. Collectively, this evidence suggests Heck catalysis by molecular or dimeric palladium as postulated by de Vries [5,20,42,43] and Schmidt [5,24] and supported by Rothenberg [44] and Fiddy [45]. Further testing to conclusively demonstrate lack of activity of nanoparticle surfaces by the use of insoluble poisons is outside the scope of this paper, but is suggested as a potentially interesting future work.…”

“…Thus, our poisoning results strongly suggest that under all conditions tested here, catalysis is solely associated with leached palladium species. Poisoning by SH-SBA-15 also implies that the active soluble catalytic species is not from nanoparticle surfaces but rather from molecular or dimeric palladium, which is consistent with the work of de Vries [20,42,43], Schmidt [24], Rothenberg [44] and Fiddy [45].…”

Di-t-butyl(ferrocenylmethyl)phosphine: air-stability, structural characterization, coordination chemistry, and application to palladium-catalyzed cross-coupling reactions

“…Much of the research focus has been centered on the use of sterically demanding tertiary alkylphosphine ligands that enhance the rate determining oxidative addition step. Ligands such as t-Bu 3 P [19][20][21][22], (o-biphenyl)PR 2 [23][24][25], BuP(1-adamantyl) 2 [26] and others [14,15,27] have been used to form catalysts that show high activities at moderate temperatures (20-100°C), even with unactivated aryl chlorides. Many of these ligands oxidize rapidly in air, so they need to be handled in an inert atmosphere or converted to the corresponding phosphonium salt [28].…”

The Heck reaction in the production of fine chemicals

“…In addition, unreactive arylating agents like aryl chlorides can be used. More variations on this theme are the use of bulky phosphite (18,41) or phosphoramidite ligands (42), carbene ligands (43,44), and pincer ligands (31,45). Another interesting, cheap, and very active class of catalysts are the palladacycles based on aromatic compounds with side chains containing N (41,46), O (47), or S (48,49).…”