Itaconate derivatives

One exception to the use of primary phosphines is in the reported syntheses of the catASium M dass of ligands 20 [46-49]. In one report, reaction of the cyclic sulfate with P(TMS)3 yields the TMS-protected secondary phospholane, which could then be reacted with the appropriate 1,2-dichloro spedes [46]. An alternative procedure to the same intermediate involves preparation of 1-phenyl-phospholane via the bismesylate, subsequent lithium-induced P-Ph deavage, and quenching with TMSC1 [49]. The ligand based on 2,3-dichloromaleic anhydride (20a originally referred to as MalPHOS [46]) has been shown to be effective for the chiral reduction of a- and /1-deliydroarnino acid derivatives and itaconate derivatives. 

As it is possible to observe in Table 3.5, the values reported are very close to 0.51, which indicates proximity to the theta condition at the air - water interface for all these poly(itaconates) derivatives. 

Although they are often considered as poorer ligands than diphosphines, they lead also to very efficient and attractive enantioselective catalytic systems as exemplified here. As recent examples, diphosphinites 19 and 20 have been involved successfully in hydrogenation of olefins (mostly itaconate derivatives and enamides, up to > 99.9 % ee) ([84-89] and functionalized ketones (21) (up to 86 % ee) [90], hydrocyanation (19) [91], standard Pd-mediated allylic alkylation (20) [92] (up to 86% ee) [93], and Diels-Alder reaction between a,/l-enals and dienes (eq. (4) 99 % ee) [94]. 

Both platinum and rhodium catalysts have been studied for enantioselective hydroformylation. The asymmetric hydroformylation of an itaconate derivative occurs with the highest selectivity in the presence of platinum catalysts (Equation 17.17). However, the chemical yields of branched aldehydes from reactions catalyzed by platinum catalysts are typically low. Therefore, enantioselective hydroformylation of mono-substituted olefins with platinum catalysts have generally been unsatisfactory, and most effort has been spent on developing rhodium catalysts for asymmetric hydroformylation. 

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