Selective Decarbonylation of Fatty Acid Esters to Linear α-Olefins

Abstract

Selective decarbonylation of p-nitrophenol esters of fatty acids to the corresponding linear α-olefins (LAOs) was achieved using palladium catalysis. After extensive ligand screening, a mixed-ligand system exploiting the trans-spanning diphosphine XantPhos and an N-heterocyclic carbene (IPr) was identified as the most effective in yielding high α-selectivity and high conversions of the ester (>98% selectivity, >90% conversion using 2.5 mol % of PdCl2 and 5 mol % of the ligands, 190 °C, 2–2.5 h). On the basis of insights from modeling at the density functional level of theory, we propose that the mixed-ligand set achieves high α-selectivity by promoting olefin dissociation from the palladium center following β-hydride elimination, which is especially facilitated both by the combined steric bias of the mixed-ligand set and by the ability of the XantPhos ligand to coordinate in both mono- and bidentate fashions.

Creating Cavities at Palladium–Phosphine Interfaces for Enhanced Selectivity in Heterogeneous Biomass Conversion

“…Previous DFT studies in homogeneous Pd catalysts 30,44 suggested dehydrogenations as rate-determining TSs, while the present work on Pd(111) surfaces points toward the C−C bond breaking process (TS-C3). Interestingly, the relative activation energies for dehydrogenation (from the prior alkyl intermediate to the corresponding TS) are quite similar for…”

“…82 Indeed, the hemilabile behavior of these ligands have been reported in homogeneous systems. 30,83 In the gas phase, the relaxed conformation of the phosphine coming from C1 is only 0.20 eV less stable than that coming from C. It is clear than the energy toll essentially emerges from the loss of Pd•••P and Pd•••C interactions after partial decoordination. Additionally, starting from the DPEPhos Me model, we included two Ph groups in the P atom that detaches from the surface to better mimic the complete DPEPhos ligand.…”

Palladium‐Catalyzed Decarbonylative Trifluoromethylation of Acid Fluorides

“…We started our investigations with the biaryl acid fluoride 1 a , utilizing Xantphos as the ligand for Pd. Although Xantphos has never been effective in catalytic trifluoromethylations, it is one of the few ligands capable of facilitating reductive elimination from [L n Pd II (Ar)(CF 3 )] ,. To our delight 15 % of the desired product ArCF 3 2 a (see Table ) was formed in our initial investigations employing TMSCF 3 as transmetalating agent.…”

The Mechanism of Rh-Catalyzed Transformation of Fatty Acids to Linear Alpha olefins

“…The highest activities and selectivities have so far been obtained with homogenous catalysts [2,14,22]. Homogeneously catalyzed decarbonylative dehydration has proven to be a promising reaction in the production of LAOs [12][13][14][15][22][23][24][25][26][27][28][29][30], as well as in the toolbox of the synthetic organic chemist [31].…”

“…With this promising outlook, transition-metal catalysts based on palladium [12][13][14][15]22,25,29,30,32], rhodium [14,23], iridium [27,33], nickel, [24,34], and iron [28] have been developed. Palladium-based catalysts have so far reached the highest activities [14].…”