Hydroalkenylation: palladium catalyzed co-dimerization of unactivated alkenes

Our Voyage from Catalytic Cross-Hydroalkenylation to Transfer-Dehydroaromatization of Cyclic π-Systems: Reactivity and Selectivity Changes Enabled by NHC-Ni and NHC-Pd Hydride Equivalents

“…cyclic olefin) by P-based systems. 38b Presumably, the problem is related to the high olefin isomerization ability of the P-M-H (e.g., M = Ni or Pd). 40 The α-olefin could only be applied in some cases with NHC ligands, such as an indene with a (NHC)Ni catalyst and OTf anion.…”

“…We noticed that the HA of cyclic olefins had been demonstrated in Pd catalysis systems since the early days. Pioneering examples employed two general approaches: (1) the alkenyl halide approach, 47 and (2) the simple olefin approach 38b (Scheme 10 ). The alkenyl halide approach employs a reductive Heck reaction catalytic cycle, which involves the oxidative addition of vinyl halides (or halogen equivalents) to Pd(0), followed by the migratory insertion of the coupling partners (i.e., dienes, alkenes, alkynes).…”

“…In contrast, in the simple olefin approach, the waste associated with the haloalkenes and reducing agents are eliminated accordingly. After sequential regio- and chemo-selective migratory insertion of alkenes and olefin donors (i.e., alkenes, alkynes), 38b,49 β-hydride elimination of the Pd complex results in the desired HA product and regenerates Pd-H catalyst.…”

“…Structural characteristics on alkene acceptors that can slow down the reversible hydrometallation step are employed to offer high chemo- and regioselectivity and avoid undesired β-H elimination. 38b 53 For instance, the use of benzylic stabilization led to the successful cross-HA between cyclohexenyl substrates and alkynes. 49c Simpler cyclohexenyl substrates are rarely applied in intermolecular HA reactions.…”

Palladium Catalysis: Dependence of the Efficiency of C−C Bond Formation on Carboxylate Ligand and Alkali Metal Carboxylate or Carboxylic Acid Additive. Part B: The Hydro(hetero)arylation, Hydroalkenylation and Hydroalkylation Reactions

“…Jung and co-workers who reported the hydroalkenylation of cyclopentene with styrene using catalytic amounts of both Pd(PPh 3 ) 4 and HBF 4 , assumed a hydridopalladium complex as the active catalytic species. [30] Gevorgyan's team also proposed a hydridopalladium complex as the species catalyzing the lightassisted hydroalkenylation of ethyl acrylate with styrene. [31] Using palladium carboxylate associated to a phosphine in the presence of tetra-butylammonium bromide, a trialkylamine and a carboxylic acid, the authors observed a determining role of the ligand and the acid (Scheme 7a).…”