- Rhodium versus iridium catalysts in the controlled tandem hydroformylation-isomerization of functionalized unsaturated fatty substrates
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The hydroformylation of 10-undecenitrile (1) and related unsaturated fatty substrates (H2C=CH(CH2)7CH2R; R=CO2Me, CH2Br, CHO) has been studied with rhodium, iridium, ruthenium, and palladium biphephos catalysts. The reactions proceeded effectively with all four systems, with high selectivities for the linear aldehyde (ratio of linear/branched aldehydes=99:1). The biphephos-bis[chloro(cyclooctadiene)iridium] system showed a non-optimized hydroformylation turnover frequency (TOFHF) of 770h-1 that was only approximately 5times lower than that of the rhodium-based system (TOFHF=3320h-1); the palladium and ruthenium biphephos systems were less active (TOFHF=210 and 310h-1, respectively). Upon recycling, remarkable productivities were achieved in both cases (TON≈58-000mol(1/1-int)-mol(Ir)-1 and 250-000mol(1/1-int)-mol(Rh)-1, in which int=internal olefin). Competitive isomerization of terminal to internal olefins occurred with these catalysts. Iridium biphephos systems allowed slightly better control of the distribution of the internal isomers than the rhodium biphephos catalyst, with higher ratios of 9-/8-undecenitrile (1-int). Place your bets now: Iridium-biphephos catalysts are highly effective in the controlled tandem isomerization-hydroformylation of 10-undecenitrile and related functionalized unsaturated fatty substrates.
- Ternel, Jrmy,Couturier, Jean-Luc,Dubois, Jean-Luc,Carpentier, Jean-Franois
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p. 513 - 520
(2015/03/04)
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- Bidentate ligands by self-assembly through hydrogen bonding: A general room temperature/ambient pressure regioselective hydroformylation of terminal alkenes
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The 6-DPPon (1)/rhodium catalyst allows for the first time a room temperature/ambient pressure regioselective hydroformylation of terminal alkenes with low catalyst loadings in good activity. The generality of this catalyst under these conditions was demonstrated for a wide range of structurally diverse alkenes equipped with many important functional groups. Thus, this practical and highly selective hydroformylation protocol, which omits the need for special pressure equipment, should find wide application in organic synthesis.
- Seiche, Wolfgang,Schuschkowski, Alexander,Breit, Bernhard
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p. 1488 - 1494
(2007/10/03)
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