Dehalogenation, using polymer-supported

The reductive dehalogenation of haloalkanes has also been achieved in high yield using polymer supported hydridoiron tetracarbonyl anion (Table 11.15). In reactions where the structure of the alkyl group is such that anionic cleavage is not favoured, carbonylation of the intermediate alkyl(hydrido)iron complex produces an aldehyde (see Chapter 8) [3]. 

Reductive dehalogenation of haloalkanes using polymer-supported hydridoiron tetracarbonyl anion... 

Five catalyst types were used in these product distribution studies Pd/C, Pd/alumina, pure Pd metal powder, Pd/Fe, and Pd/Cu/support. The last two catalysts are not traditional materials. The Pd/Cu, which was used in the reduction of nitrate, was a bimetallic catalyst on an alumina, silica, or polymer support. Fe is an atypical support in that it has the intrinsic ability to reductively dehalogenate chlorinated compounds by oxidizing to Fe2+ however, the rapid reaction rates associated with Pd/Fe are indicative of Pd-catalyzed reactions, which are much faster than Fe reactions. 

Optically active l,l -binaphthols are among the most important chiral ligands of a variety of metal species. Binaphthol-aluminum complexes have been used as chiral Lewis acid catalysts. The l,T-binaphthyl-based chiral ligands owe their success in a variety of asymmetric reactions to the chiral cavity they create around the metal center [107,108]. In contrast with the wide use of these binaphthyls, the polymer-supported variety has been less popular. The optically active and sterically regular poly(l,l -bi-naphthyls) 96 have been prepared by nickel-catalyzed dehalogenating polycondensation of dibromide monomer 95 (Sch. 7) [109] and used to prepare the polybinaphthyl aluminum(III) catalyst 97 this had much greater catalytic activity than the corresponding monomeric catalyst when used in the Mukaiyama aldol reaction (Eq. 29). Unfortunately no enantioselectivity was observed in the aldol reaction. 

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