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NON-TRADITIONAL 'GREENER' ALTERNATIVES OR ORGANIC TRANSFORMATIONS
Citation:
Varma*, R S. NON-TRADITIONAL 'GREENER' ALTERNATIVES OR ORGANIC TRANSFORMATIONS. Presented at Dept. Chemistry, Univ. of Kentucky, Lexington, KY, November 08, 2002.
Impact/Purpose:
To inform the public.
Description:
Non-traditional 'Greener' Alternatives to Organic Transformations
Synthetic organic transformations performed under non-traditional conditions are becoming popular primarily to circumvent the growing environmental concerns. 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 described 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 for multi-component reactions for rapid assembly of a library of compounds. Ultrasound-assisted solventless protocol is presented that provides ready access to non-volatile solvents, ionic liquids. 'Greener' solvents such as supercritical (sc) carbon dioxide provide an attractive media for supported metallic catalysts such as Pd/alumina for industrially significant transformations namely selective hydrogenation of maleic anhydride to g-butyrolactone. The salient eco-friendly features of these processes namely the selectivity, experimental ease of manipulation, and the enhanced reaction rates will be described.
Rajender S. Varma
lean Processes Branch, National Risk Management Research Laboratory,
US Environmental Protection Agency, MS 443, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268 USA
E-mail: Varma.Rajender@epa.gov
Synthetic organic transformations performed under non-traditional conditions are becoming popular primarily to circumvent the growing environmental concerns. 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 described 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 for multi-component reactions for rapid assembly of a library of compounds. Ultrasound-assisted solventless protocol is presented that provides ready access to non-volatile solvents, ionic liquids. 'Greener' solvents such as supercritical (sc) carbon dioxide provide an attractive media for supported metallic catalysts such as Pd/alumina for industrially significant transformations namely selective hydrogenation of maleic anhydride to g-butyrolactone. The salient eco-friendly features of these processes namely the selectivity, experimental ease of manipulation, and the enhanced reaction rates will be described.