Non-asymmetric hydroformylation

After the first hydroformylation attempts with tris(pyrrolyl)phosphine, numerous other aminophosphines with preferentially pyridyl groups or related nitrogen containing heterocycles, such as imidazols, triazols, indols, or carbazols, were prepared and tested. 

In the hydroformylation of 1-octene (CO/H2 = l l, 40bar, 108ppm [Rh], 100 °C), almost full conversion took place within 4h. The l/b ratio decreased in the order 1 (80 20) 2 (68 32) 3 (59 41). When a mixture of linear octenes was subjected to the reaction at 60 bar syngas pressure and at a temperature of 130 °C, with ligand 1 85% nonanal isomers and 11% alcohols as hydrogenation products were produced. In the reaction with pentenenitrile, as expected the 

In the hydroformylation of 2-pentene (120 C, 6h) at moderate syngas pressure (50 bar), the relevant Rh complexes behaved similar to an unmodified catalyst. At low pressures ( 25 bar), improved results were obtained particularly with P(pyrrol)3, PhP(pyrrol)2, and the fluorinated ligand. All monodentate phosphoramidites produced only moderate n-regioselectivities. 

BASF claimed the use of bidentate symmetric bisamidite ligands based on xan-thene or trypticene backbones [13]. The ligands were screened in the isomerizmg hydroformylation of isomeric butenes, pure 2-butene, 1-hexene, 1-octene, and 2-octene (Table 2.2). 

Ligand Substrate Conditions Conversion/aldehyde-selectivity (%) n-Regioselectivity (%) 

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