Resins JandaJel

The group of Janda has presented a microwave-mediated oxazole synthesis utilizing /3-ketoestcrs bound to a novel polymeric resin [57]. The desired polymer support was prepared by transesterification reactions of tert-butyl /f-ketoesters and hydroxy-butyl-functionalized JandaJel resin and subsequent standard diazo transfer. The resulting a-diazo /f-ketoesters were employed for the synthesis of an array of oxa-zoles (Scheme 7.41). 

Honigfort ME, Brittain WJ (2003) Use of JandaJel resins for copper removal in atom transfer radical polymerization. Macromolecules 36 3111... 

A similar imidazolidinone was attached by Pihko to a JandaJel resin and studied as catalyst (137, 20 mol.%) for the Diels-Alder reaction of different dienes and dienophiles with excellent enantioselectivities (70-99% ee for the major endo adduct) [344]. Except in terms of activity the performance of this catalyst was... 

Table 3. Swelling Comparison Between Gel-Type and JandaJel Resins ...

Soluble polymer-bound catalysts for epoxidation reactions have also been explored, with a complete study into the nature of the polymeric backbone performed by Janda [70]. Chiral (salen)-Mn complexes were appended to MeO-PEG, NCPS, Jan-daJeF and Merrifield resin via a glutarate spacer. It was found that for the Jacobsen epoxidation of ds-/ -mefhylstyrene, the enantioselectivities for each polymer-supported catalyst were comparable (86-90%) to commercially available Jacobsen catalyst (88%). Both soluble polymer-supported catalysts could be used twice before a decline in yield and enantioselectivity was observed. However, neither soluble polymer support proved as suitable as the insoluble JandaJel-supported (salen)-Mn complex for the epoxidation because residual impurities during precipitation and leaching of Mn from the complex, resulted in lowered yields. 

Resins with 1-2% of cross-linker (Fig. 14, A) degraded in the presence of strong Lewis acids (TMSOTf) or strong bases (BuLi). However, increasing the cross-linking level (5-10%) gave resins that were unaffected by these conditions. Resins with 1-2% of cross-linker (Fig. 14, B) showed good stability under the conditions reported above. The resin synthesized with 2% of cross-linker (Fig. 14, B) is commercialized under the name of JandaJel. 

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