4 research outputs found
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<sup>–1</sup>] 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<sup>–1</sup>) 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 PdÂ(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
PdÂ(cinnamyl)ÂClÂ(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