Comparison of Different Polymer- and Silica-Supported 9-Amino-9-deoxy- epi -quinines as Recyclable Organocatalysts

9-Amino-9-deoxy-epi-quinine,properlymodifiedbysuitablelinkers,wasanchoredonhighlycross-linkedpolystyrene,poly-(ethyleneglycol),andsilica.Theresultingspecieswerecharac-terizedbyNMRspectroscopyandtestedassupportedorgano-catalystsinthereactionbetweenisobutyricaldehydeandtrans-b-nitrostyrene.Polystyrene-andpoly(ethyleneglycol)-supportedcatalystsoutperformedtheirnonsupportedcounter-partaffordingthedesiredproductinhighyieldandee(>90î).Silica-supportedcatalystsprovedtobelessefficientintermsofbothchemicalyieldandenantioselectivity.Polystyr-ene-andpoly(ethyleneglycol)-supported9-amino-9-deoxy-epi-quininewerethenusedinthesamereactionwithdifferentsubstrates,leadingtothedesiredproductsinhighyieldandee,aswellasinthreeotherreactionsoperatingwithdifferentmechanism.Aninvestigationoftherecyclabilityofthepoly-styrene-andpoly(ethyleneglycol)-supportedsystemsshowedthatthesecouldberecoveredandrecycledwithnolossofste-reochemicalactivitybutwithamarkederosionofchemicalef-ficiencyoccurringatthefifthreactioncycle.Thiswasascribedtochemicaldegradation