Insights in the Rhodium-Catalyzed Tandem Isomerization-Hydroformylation of 10-Undecenitrile: Evidence for a Fast Isomerization Regime

Abstract

The tandem isomerization-hydroformylation of 10-undecenitrile (1) into the corresponding linear aldehyde (2) with a Rh-biphephos system was studied and the formation of internal olefin isomers (1-int-x) was monitored over time. The existence of an "isomerization phenomenon" was evidenced, where fast isomerization of 1 into up to 70% of 1-int-x followed by fast back-isomerization of 1-int-x into 1 and, in turn, into 2 occurs. This fast dynamic isomerization regime is favored at high syngas pressure (40 bar) and low biphephos-to-Rh ratio (5-10), and it is best observed at relatively high catalyst loadings ([1] 0 /[Rh] ≤ 3000). The latter regime is indeed evanescent, and gives place to a second stage in which isomerization of internal olefins (and eventual conversion into 2) proceeds much more slowly. The results are tentatively rationalized by the formation of an unstable species that promotes dynamic isomerization and which slowly vanishes or collapses into a Rh-biphephos species which is the one responsible for hydroformylation.

Silicon Carbide Supported Liquid Phase (SLP) Hydroformylation Catalysis – Effective Reaction Kinetics from Continuous Gas‐phase Operation

“…Using oleonitrile as substrate in the Rh‐bpp catalyzed hydroformylation, also Le Goanvic et al . report a positive effect of CO when syngas composition is changed from H 2 :CO of 1 : 1 to 1 : 4 at 10 bar [34] . A comparison experiment using a SILP‐Rh‐bpp catalyst ([C 2 C 1 im][NTf 2 ] as ionic liquid) showed a similar positive trend for the hydroformylation reactions (0.7 for n ‐pentanal, 0.5 for 2‐methylbutanal) while a negative effective reaction order was observed for all side reactions (see Supporting Information).…”

“…[28,33] Literature using Rh-bpp in liquid phase also showed a positive influence of CO partial pressure. [29,34] The obtained effective reaction orders were used in a rate model using the power-law approach. A training set of pressure settings at 100 °C was used to fit the unknown rate constants, and the model was tested using additional pressure settings.…”

“…This is contrary to former findings with comparable SILP hydroformylation catalysts [28,33] . Literature using Rh‐bpp in liquid phase also showed a positive influence of CO partial pressure [29,34] . The obtained effective reaction orders were used in a rate model using the power‐law approach.…”

Integration of Milstein Ru–PNN and Rh–Tribi/Tetrabi for Isomerization Linear Selective Hydroformylation of Far Internal Alkenes

“…Manipulation of the subtle interplay between the metal center and the coordination ligand is traditionally used for optimization of the desired catalysts. In this context, electron-deficient phosphorus ligands, such as Biphephos, − pyrrolyldiamidites, − and Naphos, demonstrate high activity and selectivity for α-alkenes and 2-alkenes, whereas a linear selectivity less than 90% is generally reported for challenging 3- and 4-alkenes. ,,− To enable this important process, the concept of dual-metal catalysis in which an isomerization catalyst is applied aiming at promoting the isomerization of internal alkenes to α-alkenes was introduced by Beller, Nozaki, , Vorholt, and others (Figure a). − As displayed in Figure b, Shvo’s catalyst and Pd catalyst in Rh/bisphosphite-catalyzed isomerization linear hydroformylation reactions give interesting linear selectivity, i.e., up to 90% linear selectivity obtained for challenging methyl oleate, implying the potential of such concept. Directed by our efforts in looking for another type of robust dual-catalysis system, in this paper, we reported a Milstein Ru–PNN catalyst integrated with our Rh–Tribi/Tetrabi catalysts for isomerization linear hydroformylation of 2-alkenes up to 4-alkenes, giving greatly improved linear selectivities and activities (linear selectivity improvements of 2.2–58%, up to 94.2–98.6%, and turnover number improvements of 61–335 TON, up to 385–851, Figure c) compared to the Ru–PNN/Rh–Bisbi system.…”