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GREENER CHEMICAL SYNTHESIS USING MICROWAVES
Citation:
VARMA, R. S. GREENER CHEMICAL SYNTHESIS USING MICROWAVES. Presented at 39th Annual Microwave Power Symposium, Seattle, WA, July 13 - 15, 2005.
Impact/Purpose:
To inform the public.
Description:
A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of 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. MW-assisted solventless preparation of ionic liquids and their application in alkylation and metal-catalyzed multi-component reactions is described. A novel aqueous N-alkylation of amines by alkyl halides that proceeds expeditiously in the presence of NaOH to deliver tertiary amines will be presented; the ensuing N-aryl azacycloalkanes are synthesized via a simple, efficient and eco-friendly protocol that involves double N-alkylation of amines. This green chemical reaction proceeds in the presence of aqueous potassium carbonate and the protocol can be extended to a variety of five- and even six-membered heterocyclic systems. These MW-assisted environmentally friendlier chemical transformations circumvent the need for multi-step processes that use expensive metal catalysts, utilize water as a "cleaner" reaction medium, afford excellent product