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NON-TRADITIONAL 'GREENER' ALTERNATIVES TO SYNTHETIC ORGANIC TRANSFORMATIONS USING MICROWAVES
Citation:
Varma*, R S. NON-TRADITIONAL 'GREENER' ALTERNATIVES TO SYNTHETIC ORGANIC TRANSFORMATIONS USING MICROWAVES. Chapter 6, Rashmi Sanghi, M.M.Srivastava (ed.), Green Chemistry: Environment Friendly Alternatives. Narosa Pubishing House, New Delhi, India, , 93-106.
Description:
Non-traditional 'Greener' Alternatives to synthetic Organic Transformations Using Microwaves
A rapid and environmentally friendlier approach for organic synthesis and transformations is described which involves microwave (MW) exposure of neat reactants (undiluted) often in presence of inorganic oxides as recyclable catalysts such as alumina, silica, clay, or 'doped' surfaces. A variety of deprotection, condensation, cyclization, oxidation and reduction reactions will be presented including the efficient one-pot assembly of heterocyclic molecules from in situ generated intermediates such as enamines and a-tosyloxyketones. Industrially significant compounds namely, enones, imines, enamines, nitroalkenes, oxidized sulfur species and heterocycles such as flavones, tetrahydroquinolones, 2-aroylbenzofurans, and thiazoles are easily obtainable by this methodology. The application of this solventless MW approach to multi-component reactions will be highlighted that can be adapted for high speed parallel synthesis of the library of dihydropyrimidine-2(1H)-ones and imidazo[1,2-a]annulated pyridines, pyrazines and pyrimidines. The solvent-free preparation of room temperature ionic liquids, a newer class of solvents with barely measurable vapor pressure, is also described.