Isoselective Hydroformylation of Propylene by Iodide‐Assisted Palladium Catalysis

Abstract

Isobutanal is a high value bulk material that, in principle, could be produced with 100 % atom‐economy by isoselective hydroformylation of propylene with syngas. However, leading industrial Rh‐ and Co‐catalyzed hydroformylation methods preferentially form n‐butanal over the iso‐product, and methods offering isoselectivity remain underdeveloped. Here we report an iodide‐assisted Pd‐catalyzed hydroformylation of propylene that produces isobutanal with unprecedented levels of selectivity. The method involves PdI2, simple alkyl monophosphines, such as tricyclohexylphosphine, and common green solvents, enabling the title reaction to occur with isoselectivity in up to 50 : 1 iso/n product ratios under industrially relevant conditions (80–120 °C). The catalytic and preliminary mechanistic experiments indicate a key role of the iodide anions in both the catalytic activity and the isoselectivity.

Catalytic utilization of converter gas – an industrial waste for the synthesis of pharmaceuticals

“…We believe that converter gas can be used for many other atom- and step-economical reduction transformations in the near future. In particular, converter gas from steel plants might replace natural gas sources in well-known large-scale industrial processes involving CO such as synthesis of acetic acid, 36–38 hydroformylation, 39–41 urea synthesis, 8,42–44 etc. Hopefully, this discovery will attract other researchers to develop chemical processes involving converter gas.…”

Dioxaphosphabicyclooctanes: small caged phosphines from tris(hydroxymethyl)phosphine

“…42 Recently, Dydio and co-workers showed the relevance of phosphine stereoelectronics in achieving a rare iso-selective hydroformylation of propylene. 43 Using Pd Vaska-type complexes, 44 they found that cone angle of between 152–178° and a TEP below 2060 cm −1 was crucial to achieving active catalysts.…”

Iodide-Assisted Pd Catalysis as an Attractive Alternative to Rh Catalysis for the Industrially Relevant Isoselective Hydroformylation of Simple Aliphatic Alkenes

“…the classic mononuclear catalytic cycle (rather than a binuclear mechanism as concluded in our mechanistic studies). 12…”

“…37 The observed effect was proposed to originate from the halide-assisted heterolytic splitting of dihydrogen, which facilitates the hydrogenolysis of the Pd–acyl species within the classic mononuclear catalytic cycle (rather than a binuclear mechanism as concluded in our mechanistic studies). 12…”

“…8 9 10 In sharp contrast to these efforts and inspired by our prior work, 11 we reported recently an alternative strategy for the development of isoselective methods, which is based on a monophopshine–PdI 2 catalytic system. 12 In this Synpacts article, we intend to portray the state of the art of the field, contextualize our recent contribution, and highlight the remaining challenges that need to be addressed to facilitate the industrial implementation of the devised technology.…”