Regioselectivity in the rhodium-catalyzed hydroformylation of styrene as a function of reaction temperature and gas pressure

Amino‐phosphanes in RhI‐Catalyzed Hydroformylation: New Mechanistic Insights Using D2O as Deuterium‐Labeling Agent

“…[22,37,38] Reversible 2,1 styrene insertion has previously been evidenced for hydroformylation experiments carried out under D 2 with Rh 4 (CO) 12 as the catalyst (without phosphane ligands) or with [Rh(acac)(CO) 2 ] in the presence of the mono-, diphosphane, or (R,S)-binaphos ligand. [21,23,37,38] With the latter Rh-binaphos catalytic system, the amount of α-plus β-D 1 -styrene was observed to increase significantly from 2 to 30 % when the syngas pressure was increased from 1 to 100 atm. Our results indicate that the styrene insertion becomes less reversible in the presence of phosphane ligands, with the exception of run 4.…”

“…We decided to further investigate the mechanistic details of the enantioselective process by additional experiments based on H/D isotopic exchanges using D 2 O as a deuterium source. Indeed, deuterioformylations performed in the presence of D 2 instead of H 2 have been most effective for elucidating mechanistic details in catalytic processes, for instance the degree of reversibility for the olefins insertion reactions into the Rh-H bond, [21][22][23] or the different behavior of primary, secondary, and tertiary Rh-alkyl intermediates under hydroformylation conditions. [24] In addition, the use of deuterated reagents like D 2 , EtOD, or (S)-CH 3 -CH(Ph)OD have also provided mechanistic information, respectively, in iridium-catalyzed alkane dehydrogenation, [25] in palladium-catalyzed styrene hydroalkoxycarbonylation, [26] or in metal-catalyzed hydrogen transfer from alcohols to ketones.…”

Rh-catalyzed linear hydroformylation of styrene

“…(room temperature) the kinetic, branched product is predominantly formed and deuterium labeling studies prove that the formation of both the linear and the branched alkyl species 3 is not reversible at low temperatures. 4 At higher temperatures, the insertion into the Rh-H bond becomes reversible. The branched alkyl species 3b can convert back to complex 2 under β-hydrogen elimination, whereas this happens to a far lesser extent for the linear alkyl species 3a.…”

“…Especially, using rhodium catalysts with sigma-donating ligands such as triphenylphosphine (or without phosphorus ligands) the branched product is predominantly formed. 3,4 However, especially in pharmaceutical chemistry, catalysts that selectively produce the linear aldehyde gain more and more interest, also because their synthesis via other routes is often cumbersome. The linear 3-phenylpropanal is also accessible via selective hydrogenation of the C-C double bond in cinnamaldehyde or via oxidation of the hydroxyl moiety in 3-phenylpropanol with e.g.…”

Selective hydroformylation of alkyl acrylates using [2,2′-bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl]/Rh catalyst: reversal of regioselectivity

“…Lazzaroni et al found that the formation of the linear and the branched Rhalkyl species in hydroformylation of styrene are not reversible at low temperature (equals to complexes 3i and 3ii in our case) but reversible at high temperature. 36 In order to probe the reversibility of rhodium hydride addition to coordinated ethyl acrylate, H 2 was replaced by D 2 for deuterioformylation. If hydride addition is irreversible, no deuterium could be found at the a-or b-vinyl position of the recovered ethyl acrylate.…”