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EFFICIENT CHEMICAL TRANSFORMATIONS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA
Citation:
Varma*, R S. EFFICIENT CHEMICAL TRANSFORMATIONS USING ALTERNATIVE REACTION CONDITIONS AND MEDIA. Presented at Canada-U.S. Joint Workshop , Montreal, QC, CANADA, May 20 - 21, 2004.
Impact/Purpose:
To inform the public
Description:
The diverse nature of chemical entities requires various green' strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable mineral supports such as alumina, silica, clay, or doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cyclization, rearrangement, oxidation and reduction reactions including rapid one-pot assembly of heterocyclic compounds from in situ generated reactive intermediates. The strategy is adaptable to multi-component reactions e.g. Ugi and Biginelli reactions for rapid assembly of a library of compounds. Synthesis of a wide variety of significant precursors and intermediates namely, enones, imines, enamines, nitroalkenes, and oxidized sulfur species is depicted and their value in concise synthesis of flavones, tetrahydroquinolones, 2-aroylbenzofurans, and thiazole derivatives is illustrated. Ultrasound- and MW-assisted solventless preparation of ionic liquids and their application in alkylation and metal-catalyzed multi-component reactions is described. The effectiveness of these techniques for a rapid preparation of vanadium phosphate oxide (VPO) catalysts or benign epoxidation of alkenes using hydrotelecite catalysts is presented. The case of supercritical (sc) CO2, an attractive 'Greener' media, is represented by selective hydrogenation of maleic anhydride to y-butyrolactone.