Rhodium bulky diphosphite catalysts

Table 2. Hydroformylation using rhodium bulky diphosphite catalysts ...

For lower alkenes such as 2-butenes UCC has achieved high contents of linear products (see Table 2). Bryant reported 74% selectivity for the formation of linear pentanal by hydrofonnylation of 2-butene using the rhodium bulky diphosphite catalyst [22, 23]. 

In contrast to bulky monophosphite modified systems, rhodium diphosphite catalysts showed very low activity for internal alkenes like cyclohexene. The required monodentate coordination of the ligand is... 

Among the rhodium complexes, the catalyst containing the nonsymmetrical atropisomeric phosphine-phosphite chelating ligand (1) gave the best enantioselec-tivity (up to 92% ee) in the hydroformylation of the ibuprofen precursor 4-isobutyl-styrene [2] whereas the use of the bulky diphosphite ligand 2 resulted in a remarkable regioselectivity with a branched/normal ratio of 98.5/1.5 and somewhat lower optical yield (82% ee) [3]. 

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