Asymmetric Hydroformylation Catalyzed by Highly Cross-Linked Polystyrene-Supported (R, S) -BINAPHOS-Rh (I) Complexes

Using highly cross-linked polystyrene-supported chiral phosphine-phosphite (R, S) -BINAPHOS-Rh (I) complexes, olefins were hydroformylated to give the corresponding iso-aldehydes in high ee's in benzene suspension. The efficiency in catalytic activity and selectivity is at the highest level among the heterogeneous catalysis recorded to date. In a batch equipped with a fixed bed of a polystyrene-supported (R, S) -BINAPHOS-Rh (I), gaseous substrates, cis-2-butene and 3, 3, 3-trifluoropropene, were smoothly converted into the corresponding iso-aldehydes with high selectivities (100 % regioselectivity and 80 % ee for cis-2-butene, 93 % regioselectivity and 90 % ee for 3, 3, 3-trifluoropropene) under vapor-phase reaction conditions. When the asymmetric hydroformylation of 3, 3, 3-trifluoropropene was carried out in a continuous vapor-flow column reactor, 2-trifluoromethylpropanal was obtained with 95 % regioselectivity and 90 % ee. Such less volatile olefins as styrene, vinyl acetate, 1-alkenes, polyfluorinated alkenes, were also converted into the corresponding aldehydes with high selectivities comparable to those obtained under homogeneous conditions, when they were injected through scCO2-flow column reactor in a stepwise manner. Substituents were incorporated at the phenyl groups of (R, S) -BINAPHOS. Using Rh catalysts complexed by 3-methoxy substituted ligand, olefins were hydroformylated to give iso-aldehydes, whose regio- and enantioselectivities were improved as compared with the unsubstituted ligand. Asymmetric hydroformylation of styrene with Rh (I) - (un) substituted ligands was monitored by in situ high pressure IR to disclose the aldehyde-production rate was robs = kobs [Rh] 1.0 [styrene] 0.6 [ligand] -0.1PCO-0.9 (kobs : a constant under isothermal conditions). Higher catalytic activity observed with 3-methoxy substituted ligand compared to that with normal ones is attributed to higher concentration of an active species. An alkoxy-substituted ligand was incorporated into polystyrene, and the resulting polymer-supported (R, S) -BINAPHOS-Rh (I) complex was successfully used for asymmetric hydroformylation of various olefins.