Rhodium-Catalyzed Tandem Isomerization/Hydroformylation of the Bio-Sourced 10-Undecenenitrile: Selective and Productive Catalysts for Production of Polyamide-12 Precursor.
Résumé
The hydroformylation of 10-undecenenitrile (1) - a substrate readily prepd. from renewable castor oil - in the presence of rhodium-phosphane catalysts systems is reported. The corresponding linear aldehyde (2) can be prepd. in high yields and regioselectivities with a (dicarbonyl)rhodium acetoacetonate-biphephos [Rh(acac)(CO)2-biphephos] catalyst. The hydroformylation process is accompanied by isomerization of 1 into internal isomers of undecenenitrile (1-int); yet, it is shown that the Rh-biphephos catalyst effectively isomerizes back 1-int into 1, eventually allowing high conversions of 1/1-int into 2. Recycling of the catalyst by vacuum distn. under a controlled atm. was demonstrated over 4-5 runs, leading to high productivities up to 230,000 mol (2)*mol (Rh)-1 and 5,750 mol (2)*mol (biphephos)-1. Attempted recycling of the catalyst using a thermomorphic multicomponent solvent (TMS) phase-sepn. procedure proved ineffective because the final product 2 and the Rh-biphephos catalyst were always found in the same polar phase. Auto-oxidn. of the linear aldehyde 2 into the fatty 10-cyano-2-methyldecanoic acid (5) proceeds readily upon exposure to air at room temp., opening a new effective entry toward polyamide-12. [on SciFinder(R)]