Tetrahedron report number 598 Clay and clay-supported reagents in organic synthesis Rajender S. Varma p Clean Processes Branch, National Risk Management Research Laboratory, US Environmental Protection Agency, 26WestMartinLutherKingDrive,Cincinnati,OH45268,USA Received 3 November 2001 Contents 1. Introduction 1236 2. Structure of clay minerals 1236 2.1. Layer structure 1236 2.1.1. Composition and isomorphous substitution 1236 2.2. Smectite group minerals 1236 2.2.1. Montmorillonites 1237 3. Properties of clays 1237 3.1. Ion exchange 1237 3.2. Swelling 1237 3.3. Intercalation and cation-exchange 1237 3.4. Acidity 1237 4. Pillared clays 1237 5. Supported reagents 1238 5.1. Clay-supported reagents 1238 5.1.1. `Clayfen and claycop' 1238 6. Organic reactions in clay media 1238 6.1. Oligomerization reactions 1239 6.2. Dehydration reactions 1239 6.3. Addition reactions 1239 6.4. Isomerization and rearrangement reactions 1240 6.5. Aromatic electrophilic substitution Friedel±Crafts reaction) 1240 6.6. Miscellaneous reactions Diels±Alder, Heck and Suzuki reaction) 1241 7. Basic clays 1242 8. Microwave-accelerated solvent-free organic transformations using clay-supported reagents 1243 8.1. Synthesis of imines and enamines 1243 8.2. Synthesis of imines and enamines using Envirocat EPZG w as a catalyst 1244 8.3. Oxidation of sul®des to sulfoxides using clayfen 1244 8.4. Oxidation of alcohols by clayfen 1245 8.5. Oxidation of organic substrates by claycop and hydrogen peroxide 1245 8.6. Solvent-free reductive amination of carbonyl compounds using sodium borohydride on wet clay 1245 8.7. One-pot conversion of aromatic aldehydes to nitriles using hydroxylamine±clay 1247 8.8. Cleavage of semicarbazones and phenylhydrazones with ammonium persulfate±clay 1247 8.9. DethioacetalizationÐregeneration of ketones from thioketones using clay supported nitrate salts 1248 8.10. Nitration of aromatics and selective nitration of styrenes with clayfen and clayan 1248 8.11. Rearrangement reactions pinacol±pinacolone and Beckmann) 1249 8.12. Synthesis of heterocylic compounds 1249 8.12.1. Aziridines and benzimidazoles 1249 8.12.2. Iso¯av-3-enes and ¯avones 1249 Tetrahedron 58 2002) 1235±1255 Pergamon TETRAHEDRON 0040±4020/02/$ - see front matter Published by Elsevier Science Ltd. PII: S0040-402001)01216-9 Keywords: clay; clay-supported reagents; organic synthesis; microwave irradiation. p Tel.: 11-513-487-2701; fax: 11-513-569-7677; e-mail: varma.rajender@epa.gov