A Heterogeneous Catalyst for the Transformation of Fatty Acids to α‑Olefins

Heterogeneous catalysts have so far not been very efficient [turnover frequency (TOF) < 19 h^–1] or very selective (≤60%) for α-olefin formation in deoxygenation of fatty acids. Here we report more than 20-fold higher activity (TOF = 420 h^–1) and high selectivity (>95%) for one such deoxygenation, decarbonylative dehydration, by using a heterogeneous Pd/C catalyst in the presence of phosphine ligands. The process is solvent free, allows for catalyst recycling, and does not require <i>in situ</i> distillation of the product to maintain high selectivity

Palladium Precatalysts for Decarbonylative Dehydration of Fatty Acids to Linear Alpha Olefins

Transition-metal-catalyzed decarbonylative dehydration of even-numbered fatty acids to give valuable odd-numbered alpha olefins has so far been performed using approaches in which the catalyst is formed in situ. We show that well-defined Pd­(bis-phosphine) precatalysts eliminate the need for excess phosphine and selectively produce linear alpha olefins under mild conditions and with substantially increased turnover frequency (TOF) and substrate scope. In particular, the new precatalyst Pd­(cinnamyl)­Cl­(DPEPhos) (<b>5</b>) selectively converts substrates containing unprotected aliphatic-alcohol and amine functional groups to their corresponding linear alpha olefins

Generation and Trapping of a Cage Annulated Vinylidenecarbene and Approaches to Its Cycloalkyne Isomer

A novel cage-annulated (bis-homocubyl) vinylidenecarbene has been generated and successfully trapped without any intermediacy of its cycloalkyne isomer. The greater kinetic and thermodynamic stability of the vinylidenecarbene vis-à-vis its cycloalkyne isomer has been predicted by DFT B3LYP/6-31G* calculations. The calculated results suggest the prospects of the cycloalkyne becoming amenable for trapping, if generated under suitable experimental conditions, owing to the substantial kinetic energy barrier associated with its possible ring contraction via 1,2-shift to the vinylidenecarbene isomer and marginal ground state energy difference. However, all of our attempts to directly generate and trap the cycloalkyne yielded unsatisfactory results. Attempted generation and trapping of a C2-symmetric bis-vinylidenecarbene from a bis-vinylidenedibromide met with unexpected failure

Generation and Trapping of a Cage Annulated Vinylidenecarbene and Approaches to Its Cycloalkyne Isomer

A novel cage-annulated (bis-homocubyl) vinylidenecarbene has been generated and successfully trapped without any intermediacy of its cycloalkyne isomer. The greater kinetic and thermodynamic stability of the vinylidenecarbene vis-à-vis its cycloalkyne isomer has been predicted by DFT B3LYP/6-31G* calculations. The calculated results suggest the prospects of the cycloalkyne becoming amenable for trapping, if generated under suitable experimental conditions, owing to the substantial kinetic energy barrier associated with its possible ring contraction via 1,2-shift to the vinylidenecarbene isomer and marginal ground state energy difference. However, all of our attempts to directly generate and trap the cycloalkyne yielded unsatisfactory results. Attempted generation and trapping of a C2-symmetric bis-vinylidenecarbene from a bis-vinylidenedibromide met with unexpected failure