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ENVIRONMENTALLY FRIENDLIER ORGANIC TRANSFORMATIONS ON MINERAL SUPPORTS UNDER NON-TRADITIONAL CONDITIONS
Citation:
Pillai**, U R., E SahleDemessie*, AND R S. Varma*. ENVIRONMENTALLY FRIENDLIER ORGANIC TRANSFORMATIONS ON MINERAL SUPPORTS UNDER NON-TRADITIONAL CONDITIONS. Presented at Materials Discussion No. 5, Madrid, Spain, 9/22-25/02.
Description:
Synthetic organic reactions performed under non-traditional conditions are gaining popularity primarily to circumvent the growing environmental concerns. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) either in presence of a catalyst or catalyzed by the surfaces of less-expensive and recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is described which is applicable to a wide range of deprotection, 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 for multi-component reactions for rapid assembly of a library of compounds. Alternatively, carbon dioxide provides an attractive media for supported metallic catalysts such as Pd/alumina for industrially significant transformations such as selective hydrogenation of maleic anhydride to g-butyrolactone and a,b-unsaturated ketones to a,b-unsaturated alcohols. The use of microwave and ultrasound as the energy source is described for the useful epoxidation of alkenes and a,b-unsaturated ketones over hydrotalcites. The salient eco-friendly features of these processes namely the selectivity, experimental ease of manipulation, and the enhanced reaction rates are described.