Ruthenium-catalyzed hydroformylation of the functional unsaturated fatty nitrile 10-undecenitrile

• Hydroformylation proceeds effectively with ruthenium–Biphephos systems, with very high selectivities for the linear aldehyde.
• Readily available chloro–ruthenium precursors can be used, without detrimental effect on the stability of the active species.
• Hydroformylation TOF that is ca. 1–2 orders of magnitude lower as compared to the analogous Rh-based system.

The hydroformylation of 10-undecenitrile (1), a route towards polyamide-12, has been studied using Ru-diphosphite catalysts. The reactions proceeded effectively by in situ combination of chloro precursors such as RuCl2(PPh3)3 and RuCl2(DMSO)4 with Biphephos. High productivities (TON up to 15,000 mol(aldehyde) mol(Ru)−1) were achieved by carrying the reactions at low catalyst loading ([1]0/[Ru] = 20,000), at 120 °C in toluene or acetonitrile under 20 bar CO/H2 (1:1), with 20 equiv of Biphephos vs. Ru. Up to 75% chemoselectivity for the aldehydes and very high regioselectivities for the linear aldehyde (l/b = 99:1) were reached under such optimized conditions. Lower loadings of Biphephos (down to 2.5 equiv. vs. Ru) did not affect the chemo- and regioselectivities but the activity. The Ru-Biphephos combinations showed a non-optimized hydroformylation TOFHF of ca. 2–7 min−1, that is ca. 1–2 order of magnitude lower than that of analogous Rh-based systems (TOFHF = ca. 80 min−1). These Ru-Biphephos systems are, however, incapable, under the conditions suitable for selective hydroformylation, to promote isomerization of internal olefins, and hence to achieve a tandem isomerization-hydroformylation process.

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