Citation:

Ju**,Y., AND R S. Varma*. EFFICIENT AND GREENER CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION. ISBN: 88-901804-2-0, Chapter -, R.L. Schulz and D.C. Folz (ed.), Microwave and Radio Frequency Applications; Proceedings of the Fourth World Congress on Microwave and Radio Frequency Applications, November 2004, Austin, Texas. BERTANI & C. GRAPHIC INDUSTRY, CAVIAGO, Italy, , 362-372, (2005).

Description:

The diverse nature of chemical entities requires various ‘green’ strategic pathways in our quest towards attaining sustainability. A solvent-free approach involving 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 provides a novel approach 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 and synthesis of a wide variety of precursors and intermediates namely, enones, imines, enamines, nitroalkenes, and oxidized sulfur species. A concise synthesis of flavones, tetrahydroquinolones, 2-aroylbenzofurans, and thiazole derivatives is possible. MW-assisted solventless preparation of ionic liquids conserves the use of volatile organics. A three-component solventless coupling of aldehyde, alkyne and amine (A³ coupling) has also been optimized that uses only CuBr as a catalyst. An expeditious synthesis of N-aryl azacycloalkanes, important building blocks for pharmaceuticals can be accomplished via double N-alkylation of aniline derivatives with alkyl dihalides or ditosylates to assemble two C-N bonds in a simple S_N2 heterocyclization reaction; this new methodology avoids the conventional multi-step approach and the use of expensive metal catalysts.

Record Details: